From 398a6f95b1e27f2bfc357b3ddd4c1395d81e7623 Mon Sep 17 00:00:00 2001
From: Thomas Van Lenten <thomasvl@google.com>
Date: Wed, 25 Sep 2024 16:10:39 -0700
Subject: [PATCH] Update proto files from upstream.

Using upstream 4fbb0c5eedf5658c5f3fac574b8bb0d3b3664621
---
 .../test_messages_proto2_editions.proto       |    1 +
 .../test_messages_proto3_editions.proto       |    1 +
 .../SwiftProtobuf/google/protobuf/api.proto   |    2 +-
 .../google/protobuf/descriptor.proto          |    2 +-
 .../test_messages_proto2_editions.proto       |    1 +
 .../test_messages_proto3_editions.proto       |    1 +
 Protos/upstream/google/protobuf/api.proto     |    2 +-
 .../upstream/google/protobuf/descriptor.proto |    2 +-
 .../google/protobuf/edition_unittest.proto    |    2 +
 .../upstream/google/protobuf/unittest.proto   | 2321 +++++++++++------
 .../google/protobuf/unittest_lite.proto       |    2 +
 .../protobuf/unittest_no_field_presence.proto |    7 +
 .../protobuf/unittest_proto3_arena.proto      |    1 +
 13 files changed, 1540 insertions(+), 805 deletions(-)

diff --git a/Protos/Conformance/editions/test_messages_proto2_editions.proto b/Protos/Conformance/editions/test_messages_proto2_editions.proto
index 3738b6233..23988c624 100644
--- a/Protos/Conformance/editions/test_messages_proto2_editions.proto
+++ b/Protos/Conformance/editions/test_messages_proto2_editions.proto
@@ -23,6 +23,7 @@ option objc_class_prefix = "EditionsProto2";
 
 // This is the default, but we specify it here explicitly.
 option optimize_for = SPEED;
+option cc_enable_arenas = true;
 
 // This proto includes every type of field in both singular and repeated
 // forms.
diff --git a/Protos/Conformance/editions/test_messages_proto3_editions.proto b/Protos/Conformance/editions/test_messages_proto3_editions.proto
index 0c0beceb2..c092ea6c8 100644
--- a/Protos/Conformance/editions/test_messages_proto3_editions.proto
+++ b/Protos/Conformance/editions/test_messages_proto3_editions.proto
@@ -28,6 +28,7 @@ option objc_class_prefix = "EditionsProto3";
 
 // This is the default, but we specify it here explicitly.
 option optimize_for = SPEED;
+option cc_enable_arenas = true;
 
 // This proto includes every type of field in both singular and repeated
 // forms.
diff --git a/Protos/SwiftProtobuf/google/protobuf/api.proto b/Protos/SwiftProtobuf/google/protobuf/api.proto
index 422235167..afc9cc156 100644
--- a/Protos/SwiftProtobuf/google/protobuf/api.proto
+++ b/Protos/SwiftProtobuf/google/protobuf/api.proto
@@ -166,7 +166,7 @@ message Method {
 // The mixin construct implies that all methods in `AccessControl` are
 // also declared with same name and request/response types in
 // `Storage`. A documentation generator or annotation processor will
-// see the effective `Storage.GetAcl` method after inherting
+// see the effective `Storage.GetAcl` method after inheriting
 // documentation and annotations as follows:
 //
 //     service Storage {
diff --git a/Protos/SwiftProtobuf/google/protobuf/descriptor.proto b/Protos/SwiftProtobuf/google/protobuf/descriptor.proto
index 4752e3d53..f07f9832d 100644
--- a/Protos/SwiftProtobuf/google/protobuf/descriptor.proto
+++ b/Protos/SwiftProtobuf/google/protobuf/descriptor.proto
@@ -80,7 +80,7 @@ enum Edition {
   EDITION_2024 = 1001;
 
   // Placeholder editions for testing feature resolution.  These should not be
-  // used or relyed on outside of tests.
+  // used or relied on outside of tests.
   EDITION_1_TEST_ONLY = 1;
   EDITION_2_TEST_ONLY = 2;
   EDITION_99997_TEST_ONLY = 99997;
diff --git a/Protos/upstream/editions/golden/test_messages_proto2_editions.proto b/Protos/upstream/editions/golden/test_messages_proto2_editions.proto
index 3738b6233..23988c624 100644
--- a/Protos/upstream/editions/golden/test_messages_proto2_editions.proto
+++ b/Protos/upstream/editions/golden/test_messages_proto2_editions.proto
@@ -23,6 +23,7 @@ option objc_class_prefix = "EditionsProto2";
 
 // This is the default, but we specify it here explicitly.
 option optimize_for = SPEED;
+option cc_enable_arenas = true;
 
 // This proto includes every type of field in both singular and repeated
 // forms.
diff --git a/Protos/upstream/editions/golden/test_messages_proto3_editions.proto b/Protos/upstream/editions/golden/test_messages_proto3_editions.proto
index 0c0beceb2..c092ea6c8 100644
--- a/Protos/upstream/editions/golden/test_messages_proto3_editions.proto
+++ b/Protos/upstream/editions/golden/test_messages_proto3_editions.proto
@@ -28,6 +28,7 @@ option objc_class_prefix = "EditionsProto3";
 
 // This is the default, but we specify it here explicitly.
 option optimize_for = SPEED;
+option cc_enable_arenas = true;
 
 // This proto includes every type of field in both singular and repeated
 // forms.
diff --git a/Protos/upstream/google/protobuf/api.proto b/Protos/upstream/google/protobuf/api.proto
index 422235167..afc9cc156 100644
--- a/Protos/upstream/google/protobuf/api.proto
+++ b/Protos/upstream/google/protobuf/api.proto
@@ -166,7 +166,7 @@ message Method {
 // The mixin construct implies that all methods in `AccessControl` are
 // also declared with same name and request/response types in
 // `Storage`. A documentation generator or annotation processor will
-// see the effective `Storage.GetAcl` method after inherting
+// see the effective `Storage.GetAcl` method after inheriting
 // documentation and annotations as follows:
 //
 //     service Storage {
diff --git a/Protos/upstream/google/protobuf/descriptor.proto b/Protos/upstream/google/protobuf/descriptor.proto
index 4752e3d53..f07f9832d 100644
--- a/Protos/upstream/google/protobuf/descriptor.proto
+++ b/Protos/upstream/google/protobuf/descriptor.proto
@@ -80,7 +80,7 @@ enum Edition {
   EDITION_2024 = 1001;
 
   // Placeholder editions for testing feature resolution.  These should not be
-  // used or relyed on outside of tests.
+  // used or relied on outside of tests.
   EDITION_1_TEST_ONLY = 1;
   EDITION_2_TEST_ONLY = 2;
   EDITION_99997_TEST_ONLY = 99997;
diff --git a/Protos/upstream/google/protobuf/edition_unittest.proto b/Protos/upstream/google/protobuf/edition_unittest.proto
index 81848b87e..c0d0ebbbf 100644
--- a/Protos/upstream/google/protobuf/edition_unittest.proto
+++ b/Protos/upstream/google/protobuf/edition_unittest.proto
@@ -91,6 +91,7 @@ message TestAllTypes {
 
   string optional_string_piece = 24 [ctype=STRING_PIECE];
   string optional_cord = 25 [ctype=CORD];
+  bytes optional_bytes_cord = 86 [ctype=CORD];
 
   // Defined in unittest_import_public.proto
   protobuf_unittest_import.PublicImportMessage
@@ -266,6 +267,7 @@ extend TestAllExtensions {
   // TODO: ctype=CORD is not supported for extension. Add
   // ctype=CORD option back after it is supported.
   string optional_cord_extension = 25;
+  bytes optional_bytes_cord_extension = 86;
 
   protobuf_unittest_import.PublicImportMessage
     optional_public_import_message_extension = 26;
diff --git a/Protos/upstream/google/protobuf/unittest.proto b/Protos/upstream/google/protobuf/unittest.proto
index 6e97be2f3..14cf08e09 100644
--- a/Protos/upstream/google/protobuf/unittest.proto
+++ b/Protos/upstream/google/protobuf/unittest.proto
@@ -13,27 +13,32 @@
 //
 // LINT: ALLOW_GROUPS, LEGACY_NAMES
 
-syntax = "proto2";
-
-// Some generic_services option(s) added automatically.
-// See:  http://go/proto2-generic-services-default
-option cc_generic_services = true;     // auto-added
-option java_generic_services = true;   // auto-added
-option py_generic_services = true;     // auto-added
-option cc_enable_arenas = true;
-
-import "google/protobuf/unittest_import.proto";
+edition = "2023";
 
 // We don't put this in a package within proto2 because we need to make sure
 // that the generated code doesn't depend on being in the proto2 namespace.
 // In test_util.h we do "using namespace unittest = protobuf_unittest".
 package protobuf_unittest;
 
+import "google/protobuf/unittest_import.proto";
+
+option features = {
+  enum_type: CLOSED
+  repeated_field_encoding: EXPANDED
+  utf8_validation: NONE
+};
+
+// Some generic_services option(s) added automatically.
+// See:  http://go/proto2-generic-services-default
+option cc_generic_services = true; // auto-added
+option java_generic_services = true; // auto-added
+option py_generic_services = true; // auto-added
+option cc_enable_arenas = true;
+
 // Protos optimized for SPEED use a strict superset of the generated code
 // of equivalent ones optimized for CODE_SIZE, so we should optimize all our
 // tests for speed unless explicitly testing code size optimization.
 option optimize_for = SPEED;
-
 option java_outer_classname = "UnittestProto";
 
 // This proto includes every type of field in both singular and repeated
@@ -43,113 +48,191 @@ message TestAllTypes {
     // The field name "b" fails to compile in proto1 because it conflicts with
     // a local variable named "b" in one of the generated methods.  Doh.
     // This file needs to compile in proto1 to test backwards-compatibility.
-    optional int32 bb = 1;
+    int32 bb = 1;
   }
 
   enum NestedEnum {
     FOO = 1;
     BAR = 2;
     BAZ = 3;
-    NEG = -1;  // Intentionally negative.
+    NEG = -1; // Intentionally negative.
   }
 
   // Singular
-  optional    int32 optional_int32    =  1;
-  optional    int64 optional_int64    =  2;
-  optional   uint32 optional_uint32   =  3;
-  optional   uint64 optional_uint64   =  4;
-  optional   sint32 optional_sint32   =  5;
-  optional   sint64 optional_sint64   =  6;
-  optional  fixed32 optional_fixed32  =  7;
-  optional  fixed64 optional_fixed64  =  8;
-  optional sfixed32 optional_sfixed32 =  9;
-  optional sfixed64 optional_sfixed64 = 10;
-  optional    float optional_float    = 11;
-  optional   double optional_double   = 12;
-  optional     bool optional_bool     = 13;
-  optional   string optional_string   = 14;
-  optional    bytes optional_bytes    = 15;
-
-  optional group OptionalGroup = 16 {
-    optional int32 a = 17;
+  int32 optional_int32 = 1;
+  int64 optional_int64 = 2;
+  uint32 optional_uint32 = 3;
+  uint64 optional_uint64 = 4;
+  sint32 optional_sint32 = 5;
+  sint64 optional_sint64 = 6;
+  fixed32 optional_fixed32 = 7;
+  fixed64 optional_fixed64 = 8;
+  sfixed32 optional_sfixed32 = 9;
+  sfixed64 optional_sfixed64 = 10;
+  float optional_float = 11;
+  double optional_double = 12;
+  bool optional_bool = 13;
+  string optional_string = 14;
+  bytes optional_bytes = 15;
+
+  message OptionalGroup {
+    int32 a = 17;
   }
 
-  optional NestedMessage                        optional_nested_message  = 18;
-  optional ForeignMessage                       optional_foreign_message = 19;
-  optional protobuf_unittest_import.ImportMessage optional_import_message  = 20;
-
-  optional NestedEnum                           optional_nested_enum     = 21;
-  optional ForeignEnum                          optional_foreign_enum    = 22;
-  optional protobuf_unittest_import.ImportEnum    optional_import_enum     = 23;
-
-  optional string optional_string_piece = 24 [ctype=STRING_PIECE];
-  optional string optional_cord = 25 [ctype=CORD];
+  OptionalGroup optionalgroup = 16 [
+    features.message_encoding = DELIMITED
+  ];
+
+  NestedMessage optional_nested_message = 18;
+  ForeignMessage optional_foreign_message = 19;
+  protobuf_unittest_import.ImportMessage optional_import_message = 20;
+  NestedEnum optional_nested_enum = 21;
+  ForeignEnum optional_foreign_enum = 22;
+  protobuf_unittest_import.ImportEnum optional_import_enum = 23;
+  string optional_string_piece = 24 [
+    ctype = STRING_PIECE
+  ];
+
+  string optional_cord = 25 [
+    ctype = CORD
+  ];
+  bytes optional_bytes_cord = 86 [ctype=CORD];
 
   // Defined in unittest_import_public.proto
-  optional protobuf_unittest_import.PublicImportMessage
-      optional_public_import_message = 26;
+  protobuf_unittest_import.PublicImportMessage optional_public_import_message = 26;
+  NestedMessage optional_lazy_message = 27 [
+    lazy = true
+  ];
 
-  optional NestedMessage optional_lazy_message = 27 [lazy=true];
-  optional NestedMessage optional_unverified_lazy_message = 28 [unverified_lazy=true];
+  NestedMessage optional_unverified_lazy_message = 28 [
+    unverified_lazy = true
+  ];
 
   // Repeated
-  repeated    int32 repeated_int32    = 31;
-  repeated    int64 repeated_int64    = 32;
-  repeated   uint32 repeated_uint32   = 33;
-  repeated   uint64 repeated_uint64   = 34;
-  repeated   sint32 repeated_sint32   = 35;
-  repeated   sint64 repeated_sint64   = 36;
-  repeated  fixed32 repeated_fixed32  = 37;
-  repeated  fixed64 repeated_fixed64  = 38;
+  repeated int32 repeated_int32 = 31;
+  repeated int64 repeated_int64 = 32;
+  repeated uint32 repeated_uint32 = 33;
+  repeated uint64 repeated_uint64 = 34;
+  repeated sint32 repeated_sint32 = 35;
+  repeated sint64 repeated_sint64 = 36;
+  repeated fixed32 repeated_fixed32 = 37;
+  repeated fixed64 repeated_fixed64 = 38;
   repeated sfixed32 repeated_sfixed32 = 39;
   repeated sfixed64 repeated_sfixed64 = 40;
-  repeated    float repeated_float    = 41;
-  repeated   double repeated_double   = 42;
-  repeated     bool repeated_bool     = 43;
-  repeated   string repeated_string   = 44;
-  repeated    bytes repeated_bytes    = 45;
-
-  repeated group RepeatedGroup = 46 {
-    optional int32 a = 47;
+  repeated float repeated_float = 41;
+  repeated double repeated_double = 42;
+  repeated bool repeated_bool = 43;
+  repeated string repeated_string = 44;
+  repeated bytes repeated_bytes = 45;
+
+  message RepeatedGroup {
+    int32 a = 47;
   }
 
-  repeated NestedMessage                        repeated_nested_message  = 48;
-  repeated ForeignMessage                       repeated_foreign_message = 49;
-  repeated protobuf_unittest_import.ImportMessage repeated_import_message  = 50;
+  repeated RepeatedGroup repeatedgroup = 46 [
+    features.message_encoding = DELIMITED
+  ];
 
-  repeated NestedEnum                           repeated_nested_enum     = 51;
-  repeated ForeignEnum                          repeated_foreign_enum    = 52;
-  repeated protobuf_unittest_import.ImportEnum    repeated_import_enum     = 53;
+  repeated NestedMessage repeated_nested_message = 48;
+  repeated ForeignMessage repeated_foreign_message = 49;
+  repeated protobuf_unittest_import.ImportMessage repeated_import_message = 50;
+  repeated NestedEnum repeated_nested_enum = 51;
+  repeated ForeignEnum repeated_foreign_enum = 52;
+  repeated protobuf_unittest_import.ImportEnum repeated_import_enum = 53;
+  repeated string repeated_string_piece = 54 [
+    ctype = STRING_PIECE
+  ];
 
-  repeated string repeated_string_piece = 54 [ctype=STRING_PIECE];
-  repeated string repeated_cord = 55 [ctype=CORD];
+  repeated string repeated_cord = 55 [
+    ctype = CORD
+  ];
 
-  repeated NestedMessage repeated_lazy_message = 57 [lazy=true];
+  repeated NestedMessage repeated_lazy_message = 57 [
+    lazy = true
+  ];
 
   // Singular with defaults
-  optional    int32 default_int32    = 61 [default =  41    ];
-  optional    int64 default_int64    = 62 [default =  42    ];
-  optional   uint32 default_uint32   = 63 [default =  43    ];
-  optional   uint64 default_uint64   = 64 [default =  44    ];
-  optional   sint32 default_sint32   = 65 [default = -45    ];
-  optional   sint64 default_sint64   = 66 [default =  46    ];
-  optional  fixed32 default_fixed32  = 67 [default =  47    ];
-  optional  fixed64 default_fixed64  = 68 [default =  48    ];
-  optional sfixed32 default_sfixed32 = 69 [default =  49    ];
-  optional sfixed64 default_sfixed64 = 70 [default = -50    ];
-  optional    float default_float    = 71 [default =  51.5  ];
-  optional   double default_double   = 72 [default =  52e3  ];
-  optional     bool default_bool     = 73 [default = true   ];
-  optional   string default_string   = 74 [default = "hello"];
-  optional    bytes default_bytes    = 75 [default = "world"];
-
-  optional NestedEnum  default_nested_enum  = 81 [default = BAR        ];
-  optional ForeignEnum default_foreign_enum = 82 [default = FOREIGN_BAR];
-  optional protobuf_unittest_import.ImportEnum
-      default_import_enum = 83 [default = IMPORT_BAR];
-
-  optional string default_string_piece = 84 [ctype=STRING_PIECE,default="abc"];
-  optional string default_cord = 85 [ctype=CORD,default="123"];
+  int32 default_int32 = 61 [
+    default = 41
+  ];
+
+  int64 default_int64 = 62 [
+    default = 42
+  ];
+
+  uint32 default_uint32 = 63 [
+    default = 43
+  ];
+
+  uint64 default_uint64 = 64 [
+    default = 44
+  ];
+
+  sint32 default_sint32 = 65 [
+    default = -45
+  ];
+
+  sint64 default_sint64 = 66 [
+    default = 46
+  ];
+
+  fixed32 default_fixed32 = 67 [
+    default = 47
+  ];
+
+  fixed64 default_fixed64 = 68 [
+    default = 48
+  ];
+
+  sfixed32 default_sfixed32 = 69 [
+    default = 49
+  ];
+
+  sfixed64 default_sfixed64 = 70 [
+    default = -50
+  ];
+
+  float default_float = 71 [
+    default = 51.5
+  ];
+
+  double default_double = 72 [
+    default = 5.2e4
+  ];
+
+  bool default_bool = 73 [
+    default = true
+  ];
+
+  string default_string = 74 [
+    default = "hello"
+  ];
+
+  bytes default_bytes = 75 [
+    default = "world"
+  ];
+
+  NestedEnum default_nested_enum = 81 [
+    default = BAR
+  ];
+
+  ForeignEnum default_foreign_enum = 82 [
+    default = FOREIGN_BAR
+  ];
+
+  protobuf_unittest_import.ImportEnum default_import_enum = 83 [
+    default = IMPORT_BAR
+  ];
+
+  string default_string_piece = 84 [
+    ctype = STRING_PIECE,
+    default = "abc"
+  ];
+
+  string default_cord = 85 [
+    ctype = CORD,
+    default = "123"
+  ];
 
   // For oneof test
   oneof oneof_field {
@@ -157,29 +240,54 @@ message TestAllTypes {
     NestedMessage oneof_nested_message = 112;
     string oneof_string = 113;
     bytes oneof_bytes = 114;
-    string oneof_cord = 115 [ctype=CORD];
-    string oneof_string_piece = 116 [ctype=STRING_PIECE];
-    NestedMessage oneof_lazy_nested_message = 117 [lazy=true];
+    string oneof_cord = 115 [
+      ctype = CORD
+    ];
+
+    string oneof_string_piece = 116 [
+      ctype = STRING_PIECE
+    ];
+
+    NestedMessage oneof_lazy_nested_message = 117 [
+      lazy = true
+    ];
   }
 }
 
 // This proto includes a recursively nested message.
 message NestedTestAllTypes {
-  optional NestedTestAllTypes child = 1;
-  optional TestAllTypes payload = 2;
+  NestedTestAllTypes child = 1;
+  TestAllTypes payload = 2;
   repeated NestedTestAllTypes repeated_child = 3;
-  optional NestedTestAllTypes lazy_child = 4 [lazy=true];
-  optional TestAllTypes eager_child = 5 [lazy=false];
+  NestedTestAllTypes lazy_child = 4 [
+    lazy = true
+  ];
+
+  TestAllTypes eager_child = 5 [
+    lazy = false
+  ];
 }
 
 message TestDeprecatedFields {
-  optional int32 deprecated_int32 = 1 [deprecated=true];
-  repeated string deprecated_repeated_string = 4 [deprecated=true];
-  optional TestAllTypes.NestedMessage deprecated_message = 3 [deprecated=true];
+  int32 deprecated_int32 = 1 [
+    deprecated = true
+  ];
+
+  repeated string deprecated_repeated_string = 4 [
+    deprecated = true
+  ];
+
+  TestAllTypes.NestedMessage deprecated_message = 3 [
+    deprecated = true
+  ];
+
   oneof oneof_fields {
-    int32 deprecated_int32_in_oneof = 2 [deprecated=true];
+    int32 deprecated_int32_in_oneof = 2 [
+      deprecated = true
+    ];
   }
-  optional TestDeprecatedFields nested = 5;
+
+  TestDeprecatedFields nested = 5;
 }
 
 message TestDeprecatedMessage {
@@ -189,20 +297,21 @@ message TestDeprecatedMessage {
 // Define these after TestAllTypes to make sure the compiler can handle
 // that.
 message ForeignMessage {
-  optional int32 c = 1;
-  optional int32 d = 2;
+  int32 c = 1;
+  int32 d = 2;
 }
 
 enum ForeignEnum {
   FOREIGN_FOO = 4;
   FOREIGN_BAR = 5;
   FOREIGN_BAZ = 6;
-  FOREIGN_BAX = 32;  // (1 << 32) to generate a 64b bitmask would be incorrect.
-  FOREIGN_LARGE = 123456;  // Large enough to escape the Boxed Integer cache.
+  FOREIGN_BAX = 32; // (1 << 32) to generate a 64b bitmask would be incorrect.
+  FOREIGN_LARGE = 123456; // Large enough to escape the Boxed Integer cache.
 }
 
 enum TestDeprecatedEnum {
   option deprecated = true;
+
   TEST_DEPRECATED_ENUM_UNSPECIFIED = 0;
   TEST_DEPRECATED_ENUM_VALUE1 = 1;
   TEST_DEPRECATED_ENUM_VALUE2 = 2;
@@ -210,13 +319,16 @@ enum TestDeprecatedEnum {
 
 message TestReservedFields {
   reserved 2, 15, 9 to 11;
-  reserved "bar", "baz";
+
+  reserved bar, baz;
 }
 
 enum TestReservedEnumFields {
   UNKNOWN = 0;
+
   reserved 2, 15, 9 to 11;
-  reserved "bar", "baz";
+
+  reserved bar, baz;
 }
 
 message TestAllExtensions {
@@ -225,143 +337,212 @@ message TestAllExtensions {
 
 extend TestAllExtensions {
   // Singular
-  optional    int32 optional_int32_extension    =  1;
-  optional    int64 optional_int64_extension    =  2;
-  optional   uint32 optional_uint32_extension   =  3;
-  optional   uint64 optional_uint64_extension   =  4;
-  optional   sint32 optional_sint32_extension   =  5;
-  optional   sint64 optional_sint64_extension   =  6;
-  optional  fixed32 optional_fixed32_extension  =  7;
-  optional  fixed64 optional_fixed64_extension  =  8;
-  optional sfixed32 optional_sfixed32_extension =  9;
-  optional sfixed64 optional_sfixed64_extension = 10;
-  optional    float optional_float_extension    = 11;
-  optional   double optional_double_extension   = 12;
-  optional     bool optional_bool_extension     = 13;
-  optional   string optional_string_extension   = 14;
-  optional    bytes optional_bytes_extension    = 15;
-
-  optional group OptionalGroup_extension = 16 {
-    optional int32 a = 17;
-  }
+  int32 optional_int32_extension = 1;
+  int64 optional_int64_extension = 2;
+  uint32 optional_uint32_extension = 3;
+  uint64 optional_uint64_extension = 4;
+  sint32 optional_sint32_extension = 5;
+  sint64 optional_sint64_extension = 6;
+  fixed32 optional_fixed32_extension = 7;
+  fixed64 optional_fixed64_extension = 8;
+  sfixed32 optional_sfixed32_extension = 9;
+  sfixed64 optional_sfixed64_extension = 10;
+  float optional_float_extension = 11;
+  double optional_double_extension = 12;
+  bool optional_bool_extension = 13;
+  string optional_string_extension = 14;
+  bytes optional_bytes_extension = 15;
+  OptionalGroup_extension optionalgroup_extension = 16 [
+    features.message_encoding = DELIMITED
+  ];
+
+  TestAllTypes.NestedMessage optional_nested_message_extension = 18;
+  ForeignMessage optional_foreign_message_extension = 19;
+  protobuf_unittest_import.ImportMessage optional_import_message_extension = 20;
+  TestAllTypes.NestedEnum optional_nested_enum_extension = 21;
+  ForeignEnum optional_foreign_enum_extension = 22;
+  protobuf_unittest_import.ImportEnum optional_import_enum_extension = 23;
+  string optional_string_piece_extension = 24 [
+    ctype = STRING_PIECE
+  ];
 
-  optional TestAllTypes.NestedMessage optional_nested_message_extension = 18;
-  optional ForeignMessage optional_foreign_message_extension = 19;
-  optional protobuf_unittest_import.ImportMessage
-    optional_import_message_extension = 20;
-
-  optional TestAllTypes.NestedEnum optional_nested_enum_extension = 21;
-  optional ForeignEnum optional_foreign_enum_extension = 22;
-  optional protobuf_unittest_import.ImportEnum
-    optional_import_enum_extension = 23;
-
-  optional string optional_string_piece_extension = 24 [ctype=STRING_PIECE];
   // TODO: ctype=CORD is not supported for extension. Add
   // ctype=CORD option back after it is supported.
-  optional string optional_cord_extension = 25;
+  string optional_cord_extension = 25;
+  bytes optional_bytes_cord_extension = 86;
 
-  optional protobuf_unittest_import.PublicImportMessage
-    optional_public_import_message_extension = 26;
+  protobuf_unittest_import.PublicImportMessage
+      optional_public_import_message_extension = 26;
+  TestAllTypes.NestedMessage optional_lazy_message_extension = 27 [
+    lazy = true
+  ];
 
-  optional TestAllTypes.NestedMessage
-    optional_lazy_message_extension = 27 [lazy=true];
-  optional TestAllTypes.NestedMessage
-    optional_unverified_lazy_message_extension = 28 [unverified_lazy=true];
+  TestAllTypes.NestedMessage optional_unverified_lazy_message_extension = 28 [
+    unverified_lazy = true
+  ];
 
   // Repeated
-  repeated    int32 repeated_int32_extension    = 31;
-  repeated    int64 repeated_int64_extension    = 32;
-  repeated   uint32 repeated_uint32_extension   = 33;
-  repeated   uint64 repeated_uint64_extension   = 34;
-  repeated   sint32 repeated_sint32_extension   = 35;
-  repeated   sint64 repeated_sint64_extension   = 36;
-  repeated  fixed32 repeated_fixed32_extension  = 37;
-  repeated  fixed64 repeated_fixed64_extension  = 38;
+  repeated int32 repeated_int32_extension = 31;
+  repeated int64 repeated_int64_extension = 32;
+  repeated uint32 repeated_uint32_extension = 33;
+  repeated uint64 repeated_uint64_extension = 34;
+  repeated sint32 repeated_sint32_extension = 35;
+  repeated sint64 repeated_sint64_extension = 36;
+  repeated fixed32 repeated_fixed32_extension = 37;
+  repeated fixed64 repeated_fixed64_extension = 38;
   repeated sfixed32 repeated_sfixed32_extension = 39;
   repeated sfixed64 repeated_sfixed64_extension = 40;
-  repeated    float repeated_float_extension    = 41;
-  repeated   double repeated_double_extension   = 42;
-  repeated     bool repeated_bool_extension     = 43;
-  repeated   string repeated_string_extension   = 44;
-  repeated    bytes repeated_bytes_extension    = 45;
-
-  repeated group RepeatedGroup_extension = 46 {
-    optional int32 a = 47;
-  }
+  repeated float repeated_float_extension = 41;
+  repeated double repeated_double_extension = 42;
+  repeated bool repeated_bool_extension = 43;
+  repeated string repeated_string_extension = 44;
+  repeated bytes repeated_bytes_extension = 45;
+  repeated RepeatedGroup_extension repeatedgroup_extension = 46 [
+    features.message_encoding = DELIMITED
+  ];
 
   repeated TestAllTypes.NestedMessage repeated_nested_message_extension = 48;
   repeated ForeignMessage repeated_foreign_message_extension = 49;
   repeated protobuf_unittest_import.ImportMessage
-    repeated_import_message_extension = 50;
-
+      repeated_import_message_extension = 50;
   repeated TestAllTypes.NestedEnum repeated_nested_enum_extension = 51;
   repeated ForeignEnum repeated_foreign_enum_extension = 52;
-  repeated protobuf_unittest_import.ImportEnum
-    repeated_import_enum_extension = 53;
+  repeated protobuf_unittest_import.ImportEnum repeated_import_enum_extension = 53;
+  repeated string repeated_string_piece_extension = 54 [
+    ctype = STRING_PIECE
+  ];
 
-  repeated string repeated_string_piece_extension = 54 [ctype=STRING_PIECE];
   // TODO: ctype=CORD is not supported for extension. Add
   // ctype=CORD option back after it is supported.
   repeated string repeated_cord_extension = 55;
-
-  repeated TestAllTypes.NestedMessage
-    repeated_lazy_message_extension = 57 [lazy=true];
+  repeated TestAllTypes.NestedMessage repeated_lazy_message_extension = 57 [
+    lazy = true
+  ];
 
   // Singular with defaults
-  optional    int32 default_int32_extension    = 61 [default =  41    ];
-  optional    int64 default_int64_extension    = 62 [default =  42    ];
-  optional   uint32 default_uint32_extension   = 63 [default =  43    ];
-  optional   uint64 default_uint64_extension   = 64 [default =  44    ];
-  optional   sint32 default_sint32_extension   = 65 [default = -45    ];
-  optional   sint64 default_sint64_extension   = 66 [default =  46    ];
-  optional  fixed32 default_fixed32_extension  = 67 [default =  47    ];
-  optional  fixed64 default_fixed64_extension  = 68 [default =  48    ];
-  optional sfixed32 default_sfixed32_extension = 69 [default =  49    ];
-  optional sfixed64 default_sfixed64_extension = 70 [default = -50    ];
-  optional    float default_float_extension    = 71 [default =  51.5  ];
-  optional   double default_double_extension   = 72 [default =  52e3  ];
-  optional     bool default_bool_extension     = 73 [default = true   ];
-  optional   string default_string_extension   = 74 [default = "hello"];
-  optional    bytes default_bytes_extension    = 75 [default = "world"];
-
-  optional TestAllTypes.NestedEnum
-    default_nested_enum_extension = 81 [default = BAR];
-  optional ForeignEnum
-    default_foreign_enum_extension = 82 [default = FOREIGN_BAR];
-  optional protobuf_unittest_import.ImportEnum
-    default_import_enum_extension = 83 [default = IMPORT_BAR];
-
-  optional string default_string_piece_extension = 84 [ctype=STRING_PIECE,
-                                                       default="abc"];
+  int32 default_int32_extension = 61 [
+    default = 41
+  ];
+
+  int64 default_int64_extension = 62 [
+    default = 42
+  ];
+
+  uint32 default_uint32_extension = 63 [
+    default = 43
+  ];
+
+  uint64 default_uint64_extension = 64 [
+    default = 44
+  ];
+
+  sint32 default_sint32_extension = 65 [
+    default = -45
+  ];
+
+  sint64 default_sint64_extension = 66 [
+    default = 46
+  ];
+
+  fixed32 default_fixed32_extension = 67 [
+    default = 47
+  ];
+
+  fixed64 default_fixed64_extension = 68 [
+    default = 48
+  ];
+
+  sfixed32 default_sfixed32_extension = 69 [
+    default = 49
+  ];
+
+  sfixed64 default_sfixed64_extension = 70 [
+    default = -50
+  ];
+
+  float default_float_extension = 71 [
+    default = 51.5
+  ];
+
+  double default_double_extension = 72 [
+    default = 5.2e4
+  ];
+
+  bool default_bool_extension = 73 [
+    default = true
+  ];
+
+  string default_string_extension = 74 [
+    default = "hello"
+  ];
+
+  bytes default_bytes_extension = 75 [
+    default = "world"
+  ];
+
+  TestAllTypes.NestedEnum default_nested_enum_extension = 81 [
+    default = BAR
+  ];
+
+  ForeignEnum default_foreign_enum_extension = 82 [
+    default = FOREIGN_BAR
+  ];
+
+  protobuf_unittest_import.ImportEnum default_import_enum_extension = 83 [
+    default = IMPORT_BAR
+  ];
+
+  string default_string_piece_extension = 84 [
+    ctype = STRING_PIECE,
+    default = "abc"
+  ];
+
   // TODO: ctype=CORD is not supported for extension. Add
   // ctype=CORD option back after it is supported.
-  optional string default_cord_extension = 85 [default="123"];
+  string default_cord_extension = 85 [
+    default = "123"
+  ];
 
   // For oneof test
-  optional uint32 oneof_uint32_extension = 111;
-  optional TestAllTypes.NestedMessage oneof_nested_message_extension = 112;
-  optional string oneof_string_extension = 113;
-  optional bytes oneof_bytes_extension = 114;
+  uint32 oneof_uint32_extension = 111;
+  TestAllTypes.NestedMessage oneof_nested_message_extension = 112;
+  string oneof_string_extension = 113;
+  bytes oneof_bytes_extension = 114;
+}
+
+message OptionalGroup_extension {
+  int32 a = 17;
+}
+
+message RepeatedGroup_extension {
+  int32 a = 47;
 }
 
 message TestMixedFieldsAndExtensions {
-  optional int32 a = 1;
+  int32 a = 1;
   repeated fixed32 b = 3;
+
   extensions 2, 4;
+
   extend TestMixedFieldsAndExtensions {
-    optional int32 c = 2;
+    int32 c = 2;
     repeated fixed32 d = 4;
   }
 }
 
 message TestGroup {
-  optional group OptionalGroup = 16 {
-    optional int32 a = 17;
-    optional int32 zz = 89;  // fast table size must be at least 16, for this
-                             // field to be parsed by the fast parser, since
-                             // 89 - 17 = 72 is a multiple of 8.
+  message OptionalGroup {
+    int32 a = 17;
+    int32 zz = 89;  // fast table size must be at least 16, for this
+                    // field to be parsed by the fast parser, since
+                    // 89 - 17 = 72 is a multiple of 8.
   }
-  optional ForeignEnum optional_foreign_enum = 22;
+
+  OptionalGroup optionalgroup = 16 [
+    features.message_encoding = DELIMITED
+  ];
+
+  ForeignEnum optional_foreign_enum = 22;
 }
 
 message TestGroupExtension {
@@ -372,24 +553,32 @@ message TestNestedExtension {
   extend TestAllExtensions {
     // Check for bug where string extensions declared in tested scope did not
     // compile.
-    optional string test = 1002 [default="test"];
+    string test = 1002 [
+      default = "test"
+    ];
+
     // Used to test if generated extension name is correct when there are
     // underscores.
-    optional string nested_string_extension = 1003;
+    string nested_string_extension = 1003;
   }
 
   extend TestGroupExtension {
-    optional group OptionalGroup_extension = 16 {
-      optional int32 a = 17;
-    }
-    optional ForeignEnum optional_foreign_enum_extension = 22;
+    OptionalGroup_extension optionalgroup_extension = 16 [
+      features.message_encoding = DELIMITED
+    ];
+
+    ForeignEnum optional_foreign_enum_extension = 22;
+  }
+
+  message OptionalGroup_extension {
+    int32 a = 17;
   }
 }
 
 message TestChildExtension {
-  optional string a = 1;
-  optional string b = 2;
-  optional TestAllExtensions optional_extension = 3;
+  string a = 1;
+  string b = 2;
+  TestAllExtensions optional_extension = 3;
 }
 
 // Emulates wireformat data of TestChildExtension with dynamic extension
@@ -397,35 +586,60 @@ message TestChildExtension {
 message TestChildExtensionData {
   message NestedTestAllExtensionsData {
     message NestedDynamicExtensions {
-      optional int32 a = 1;
-      optional int32 b = 2;
+      int32 a = 1;
+      int32 b = 2;
     }
-    optional NestedDynamicExtensions dynamic = 409707008;
+
+    NestedDynamicExtensions dynamic = 409707008;
   }
-  optional string a = 1;
-  optional string b = 2;
-  optional NestedTestAllExtensionsData optional_extension = 3;
+
+  string a = 1;
+  string b = 2;
+  NestedTestAllExtensionsData optional_extension = 3;
 }
 
 message TestNestedChildExtension {
-  optional int32 a = 1;
-  optional TestChildExtension child = 2;
+  int32 a = 1;
+  TestChildExtension child = 2;
 }
 
 // Emulates wireformat data of TestNestedChildExtension with dynamic extension
 // (DynamicExtension).
 message TestNestedChildExtensionData {
-  optional int32 a = 1;
-  optional TestChildExtensionData child = 2;
+  int32 a = 1;
+  TestChildExtensionData child = 2;
 }
 
 // Required and closed enum fields are considered unknown fields if the value is
 // not valid. We need to make sure it functions as expected.
 message TestRequiredEnum {
-  required ForeignEnum required_enum = 1;
+  ForeignEnum required_enum = 1 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
+
+  // A dummy optional field.
+  int32 a = 2;
+}
+
+// Required and open enum accepts invalid enum values.
+enum ForeignOpenEnum {
+  option features.enum_type = OPEN;
+
+  FOREIGN_OPEN_UNKNOWN = 0;
+  FOREIGN_OPEN_FOO = 4;
+  FOREIGN_OPEN_BAR = 5;
+  FOREIGN_OPEN_BAZ = 6;
+  FOREIGN_OPEN_BAX = 32;  // (1 << 32) to generate a 64b bitmask would be
+                          // incorrect.
+}
+
+message TestRequiredOpenEnum {
+  ForeignOpenEnum required_enum = 1 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
 
   // A dummy optional field.
-  optional int32 a = 2;
+  int32 a = 2;
 }
 
 // TestRequiredEnum + using enum values that won't fit to 64 bitmask.
@@ -434,13 +648,15 @@ message TestRequiredEnumNoMask {
     UNSPECIFIED = 0;
     FOO = 2;
     BAR = 100;
-    BAZ = -1;  // Intentionally negative.
+    BAZ = -1; // Intentionally negative.
   }
 
-  required NestedEnum required_enum = 1;
+  NestedEnum required_enum = 1 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
 
   // A dummy optional field.
-  optional int32 a = 2;
+  int32 a = 2;
 }
 
 message TestRequiredEnumMulti {
@@ -453,10 +669,18 @@ message TestRequiredEnumMulti {
 
   // Intentionally placed in descending field number to force sorting in closed
   // enum verification.
-  required NestedEnum required_enum_4 = 4;
-  optional int32 a_3 = 3;
-  required NestedEnum required_enum_2 = 2;
-  required ForeignEnum required_enum_1 = 1;
+  NestedEnum required_enum_4 = 4 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
+
+  int32 a_3 = 3;
+  NestedEnum required_enum_2 = 2 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
+
+  ForeignEnum required_enum_1 = 1 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
 }
 
 message TestRequiredNoMaskMulti {
@@ -470,14 +694,30 @@ message TestRequiredNoMaskMulti {
   // Intentionally placed in descending field number to force sorting in closed
   // enum verification. Also, using large field numbers to use tag only
   // matching for required fields.
-  required fixed32 required_fixed32_80 = 80;
-  required fixed32 required_fixed32_70 = 70;
+  fixed32 required_fixed32_80 = 80 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
+
+  fixed32 required_fixed32_70 = 70 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
+
+  NestedEnum required_enum_64 = 64 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
+
+  NestedEnum required_enum_4 = 4 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
 
-  required NestedEnum required_enum_64 = 64;
-  required NestedEnum required_enum_4 = 4;
-  optional int32 a_3 = 3;
-  required NestedEnum required_enum_2 = 2;
-  required ForeignEnum required_enum_1 = 1;
+  int32 a_3 = 3;
+  NestedEnum required_enum_2 = 2 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
+
+  ForeignEnum required_enum_1 = 1 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
 }
 
 // We have separate messages for testing required fields because it's
@@ -486,82 +726,93 @@ message TestRequiredNoMaskMulti {
 // required filed because the code output is basically identical to
 // optional fields for all types.
 message TestRequired {
-  required int32 a = 1;
-  optional int32 dummy2 = 2;
-  required int32 b = 3;
+  int32 a = 1 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
+
+  int32 dummy2 = 2;
+  int32 b = 3 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
 
   extend TestAllExtensions {
-    optional TestRequired single = 1000;
-    repeated TestRequired multi  = 1001;
+    TestRequired single = 1000;
+    repeated TestRequired multi = 1001;
   }
 
   // Pad the field count to 32 so that we can test that IsInitialized()
   // properly checks multiple elements of has_bits_.
-  optional int32 dummy4  =  4;
-  optional int32 dummy5  =  5;
-  optional int32 dummy6  =  6;
-  optional int32 dummy7  =  7;
-  optional int32 dummy8  =  8;
-  optional int32 dummy9  =  9;
-  optional int32 dummy10 = 10;
-  optional int32 dummy11 = 11;
-  optional int32 dummy12 = 12;
-  optional int32 dummy13 = 13;
-  optional int32 dummy14 = 14;
-  optional int32 dummy15 = 15;
-  optional int32 dummy16 = 16;
-  optional int32 dummy17 = 17;
-  optional int32 dummy18 = 18;
-  optional int32 dummy19 = 19;
-  optional int32 dummy20 = 20;
-  optional int32 dummy21 = 21;
-  optional int32 dummy22 = 22;
-  optional int32 dummy23 = 23;
-  optional int32 dummy24 = 24;
-  optional int32 dummy25 = 25;
-  optional int32 dummy26 = 26;
-  optional int32 dummy27 = 27;
-  optional int32 dummy28 = 28;
-  optional int32 dummy29 = 29;
-  optional int32 dummy30 = 30;
-  optional int32 dummy31 = 31;
-  optional int32 dummy32 = 32;
-
-  required int32 c = 33;
+  int32 dummy4 = 4;
+  int32 dummy5 = 5;
+  int32 dummy6 = 6;
+  int32 dummy7 = 7;
+  int32 dummy8 = 8;
+  int32 dummy9 = 9;
+  int32 dummy10 = 10;
+  int32 dummy11 = 11;
+  int32 dummy12 = 12;
+  int32 dummy13 = 13;
+  int32 dummy14 = 14;
+  int32 dummy15 = 15;
+  int32 dummy16 = 16;
+  int32 dummy17 = 17;
+  int32 dummy18 = 18;
+  int32 dummy19 = 19;
+  int32 dummy20 = 20;
+  int32 dummy21 = 21;
+  int32 dummy22 = 22;
+  int32 dummy23 = 23;
+  int32 dummy24 = 24;
+  int32 dummy25 = 25;
+  int32 dummy26 = 26;
+  int32 dummy27 = 27;
+  int32 dummy28 = 28;
+  int32 dummy29 = 29;
+  int32 dummy30 = 30;
+  int32 dummy31 = 31;
+  int32 dummy32 = 32;
+  int32 c = 33 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
 
   // Add an optional child message to make this non-trivial for go/pdlazy.
-  optional ForeignMessage optional_foreign = 34;
+  ForeignMessage optional_foreign = 34;
 }
 
 message TestRequiredForeign {
-  optional TestRequired optional_message = 1;
+  TestRequired optional_message = 1;
   repeated TestRequired repeated_message = 2;
-  optional int32 dummy = 3;
+  int32 dummy = 3;
 
   // Missing required fields must not affect verification of child messages.
-  optional NestedTestAllTypes optional_lazy_message = 4 [lazy = true];
+  NestedTestAllTypes optional_lazy_message = 4 [
+    lazy = true
+  ];
 }
 
 message TestRequiredMessage {
-  optional TestRequired optional_message = 1;
+  TestRequired optional_message = 1;
   repeated TestRequired repeated_message = 2;
-  required TestRequired required_message = 3;
+  TestRequired required_message = 3 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
 }
 
 message TestNestedRequiredForeign {
-  optional TestNestedRequiredForeign child = 1;
-  optional TestRequiredForeign payload = 2;
-  optional int32 dummy = 3;
+  TestNestedRequiredForeign child = 1;
+  TestRequiredForeign payload = 2;
+  int32 dummy = 3;
+
   // optional message to test required closed enum.
-  optional TestRequiredEnum required_enum = 5;
-  optional TestRequiredEnumNoMask required_enum_no_mask = 6;
-  optional TestRequiredEnumMulti required_enum_multi = 7;
-  optional TestRequiredNoMaskMulti required_no_mask = 9;
+  TestRequiredEnum required_enum = 5;
+  TestRequiredEnumNoMask required_enum_no_mask = 6;
+  TestRequiredEnumMulti required_enum_multi = 7;
+  TestRequiredNoMaskMulti required_no_mask = 9;
 }
 
 // Test that we can use NestedMessage from outside TestAllTypes.
 message TestForeignNested {
-  optional TestAllTypes.NestedMessage foreign_nested = 1;
+  TestAllTypes.NestedMessage foreign_nested = 1;
 }
 
 // TestEmptyMessage is used to test unknown field support.
@@ -577,9 +828,10 @@ message TestEmptyMessageWithExtensions {
 // Needed for a Python test.
 message TestPickleNestedMessage {
   message NestedMessage {
-    optional int32 bb = 1;
+    int32 bb = 1;
+
     message NestedNestedMessage {
-      optional int32 cc = 1;
+      int32 cc = 1;
     }
   }
 }
@@ -594,81 +846,114 @@ message TestMultipleExtensionRanges {
 message TestReallyLargeTagNumber {
   // The largest possible tag number is 2^28 - 1, since the wire format uses
   // three bits to communicate wire type.
-  optional int32 a = 1;
-  optional int32 bb = 268435455;
+  int32 a = 1;
+  int32 bb = 268435455;
 }
 
 message TestRecursiveMessage {
-  optional TestRecursiveMessage a = 1;
-  optional int32 i = 2;
+  TestRecursiveMessage a = 1;
+  int32 i = 2;
 }
 
 // Test that mutual recursion works.
 message TestMutualRecursionA {
   message SubMessage {
-    optional TestMutualRecursionB b = 1;
+    TestMutualRecursionB b = 1;
   }
-  optional TestMutualRecursionB bb = 1;
-  optional group SubGroup = 2 {
-    optional SubMessage sub_message = 3;  // Needed because of bug in javatest
-    optional TestAllTypes not_in_this_scc = 4;
+
+  TestMutualRecursionB bb = 1;
+
+  message SubGroup {
+    SubMessage sub_message = 3; // Needed because of bug in javatest
+    TestAllTypes not_in_this_scc = 4;
   }
-  repeated group SubGroupR = 5 {
-    optional TestAllTypes payload = 6;
+
+  SubGroup subgroup = 2 [
+    features.message_encoding = DELIMITED
+  ];
+
+  message SubGroupR {
+    TestAllTypes payload = 6;
   }
+
+  repeated SubGroupR subgroupr = 5 [
+    features.message_encoding = DELIMITED
+  ];
 }
 
 message TestMutualRecursionB {
-  optional TestMutualRecursionA a = 1;
-  optional int32 optional_int32 = 2;
+  TestMutualRecursionA a = 1;
+  int32 optional_int32 = 2;
 }
 
 message TestIsInitialized {
   message SubMessage {
-    optional group SubGroup = 1 {
-      required int32 i = 2;
+    message SubGroup {
+      int32 i = 2 [
+        features.field_presence = LEGACY_REQUIRED
+      ];
     }
+
+    SubGroup subgroup = 1 [
+      features.message_encoding = DELIMITED
+    ];
   }
-  optional SubMessage sub_message = 1;
+
+  SubMessage sub_message = 1;
 }
 
 // Test that groups have disjoint field numbers from their siblings and
 // parents.  This is NOT possible in proto1; only google.protobuf.  When attempting
 // to compile with proto1, this will emit an error; so we only include it
 // in protobuf_unittest_proto.
-message TestDupFieldNumber {                        // NO_PROTO1
-  optional int32 a = 1;                             // NO_PROTO1
-  optional group Foo = 2 { optional int32 a = 1; }  // NO_PROTO1
-  optional group Bar = 3 { optional int32 a = 1; }  // NO_PROTO1
-}                                                   // NO_PROTO1
+message TestDupFieldNumber {// NO_PROTO1
+  int32 a = 1; // NO_PROTO1
+  message Foo { // NO_PROTO1
+    int32 a = 1; // NO_PROTO1
+  } // NO_PROTO1
+  Foo foo = 2 [features.message_encoding = DELIMITED]; // NO_PROTO1
+  message Bar { // NO_PROTO1
+    int32 a = 1; // NO_PROTO1
+  } // NO_PROTO1
+  Bar bar = 3 [features.message_encoding = DELIMITED]; // NO_PROTO1
+} // NO_PROTO1
 
 // Additional messages for testing lazy fields.
 message TestEagerMessage {
-  optional TestAllTypes sub_message = 1 [lazy=false];
+  TestAllTypes sub_message = 1 [
+    lazy = false
+  ];
 }
+
 message TestLazyMessage {
-  optional TestAllTypes sub_message = 1 [lazy=true];
+  TestAllTypes sub_message = 1 [
+    lazy = true
+  ];
 }
+
 message TestLazyMessageRepeated {
   repeated TestLazyMessage repeated_message = 1;
 }
+
 message TestEagerMaybeLazy {
   message NestedMessage {
-    optional TestPackedTypes packed = 1;
+    TestPackedTypes packed = 1;
   }
-  optional TestAllTypes message_foo = 1;
-  optional TestAllTypes message_bar = 2;
-  optional NestedMessage message_baz = 3;
+
+  TestAllTypes message_foo = 1;
+  TestAllTypes message_bar = 2;
+  NestedMessage message_baz = 3;
 }
+
 // Needed for a Python test.
 message TestNestedMessageHasBits {
   message NestedMessage {
     repeated int32 nestedmessage_repeated_int32 = 1;
     repeated ForeignMessage nestedmessage_repeated_foreignmessage = 2;
   }
-  optional NestedMessage optional_nested_message = 1;
-}
 
+  NestedMessage optional_nested_message = 1;
+}
 
 // Test an enum that has multiple values with the same number.
 enum TestEnumWithDupValue {
@@ -695,122 +980,217 @@ enum TestSparseEnum {
 // Test message with CamelCase field names.  This violates Protocol Buffer
 // standard style.
 message TestCamelCaseFieldNames {
-  optional int32 PrimitiveField = 1;
-  optional string StringField = 2;
-  optional ForeignEnum EnumField = 3;
-  optional ForeignMessage MessageField = 4;
-  optional string StringPieceField = 5 [ctype=STRING_PIECE];
-  optional string CordField = 6 [ctype=CORD];
+  int32 PrimitiveField = 1;
+  string StringField = 2;
+  ForeignEnum EnumField = 3;
+  ForeignMessage MessageField = 4;
+  string StringPieceField = 5 [
+    ctype = STRING_PIECE
+  ];
+
+  string CordField = 6 [
+    ctype = CORD
+  ];
 
   repeated int32 RepeatedPrimitiveField = 7;
   repeated string RepeatedStringField = 8;
   repeated ForeignEnum RepeatedEnumField = 9;
   repeated ForeignMessage RepeatedMessageField = 10;
-  repeated string RepeatedStringPieceField = 11 [ctype=STRING_PIECE];
-  repeated string RepeatedCordField = 12 [ctype=CORD];
-}
+  repeated string RepeatedStringPieceField = 11 [
+    ctype = STRING_PIECE
+  ];
 
+  repeated string RepeatedCordField = 12 [
+    ctype = CORD
+  ];
+}
 
 // We list fields out of order, to ensure that we're using field number and not
 // field index to determine serialization order.
 message TestFieldOrderings {
-  optional string my_string = 11;
+  string my_string = 11;
+
   extensions 2 to 10;
-  optional int64 my_int = 1;
+
+  int64 my_int = 1;
+
   extensions 12 to 100;
-  optional float my_float = 101;
+
+  float my_float = 101;
+
   message NestedMessage {
-    optional int64 oo = 2;
+    int64 oo = 2;
+
     // The field name "b" fails to compile in proto1 because it conflicts with
     // a local variable named "b" in one of the generated methods.  Doh.
     // This file needs to compile in proto1 to test backwards-compatibility.
-    optional int32 bb = 1;
+    int32 bb = 1;
   }
 
-  optional NestedMessage optional_nested_message  = 200;
+  NestedMessage optional_nested_message = 200;
 }
 
 extend TestFieldOrderings {
-  optional string my_extension_string = 50;
-  optional int32 my_extension_int = 5;
+  string my_extension_string = 50;
+  int32 my_extension_int = 5;
 }
 
 message TestExtensionOrderings1 {
   extend TestFieldOrderings {
-    optional TestExtensionOrderings1 test_ext_orderings1 = 13;
+    TestExtensionOrderings1 test_ext_orderings1 = 13;
   }
-  optional string my_string = 1;
+
+  string my_string = 1;
 }
 
 message TestExtensionOrderings2 {
   extend TestFieldOrderings {
-    optional TestExtensionOrderings2 test_ext_orderings2 = 12;
+    TestExtensionOrderings2 test_ext_orderings2 = 12;
   }
+
   message TestExtensionOrderings3 {
     extend TestFieldOrderings {
-      optional TestExtensionOrderings3 test_ext_orderings3 = 14;
+      TestExtensionOrderings3 test_ext_orderings3 = 14;
     }
-    optional string my_string = 1;
+
+    string my_string = 1;
   }
-  optional string my_string = 1;
+
+  string my_string = 1;
 }
 
 message TestExtremeDefaultValues {
-  optional bytes escaped_bytes = 1 [default = "\0\001\a\b\f\n\r\t\v\\\'\"\xfe"];
-  optional uint32 large_uint32 = 2 [default = 0xFFFFFFFF];
-  optional uint64 large_uint64 = 3 [default = 0xFFFFFFFFFFFFFFFF];
-  optional  int32 small_int32  = 4 [default = -0x7FFFFFFF];
-  optional  int64 small_int64  = 5 [default = -0x7FFFFFFFFFFFFFFF];
-  optional  int32 really_small_int32 = 21 [default = -0x80000000];
-  optional  int64 really_small_int64 = 22 [default = -0x8000000000000000];
+  bytes escaped_bytes = 1 [
+    default =
+        "\0\001\a\b\f\n\r\t\v\\\'\"\xfe"
+  ];
+
+  uint32 large_uint32 = 2 [
+    default = 0xFFFFFFFF
+  ];
+
+  uint64 large_uint64 = 3 [
+    default = 0xFFFFFFFFFFFFFFFF
+  ];
+
+  int32 small_int32 = 4 [
+    default = -0x7FFFFFFF
+  ];
+
+  int64 small_int64 = 5 [
+    default = -0x7FFFFFFFFFFFFFFF
+  ];
+
+  int32 really_small_int32 = 21 [
+    default = -0x80000000
+  ];
+
+  int64 really_small_int64 = 22 [
+    default = -0x8000000000000000
+  ];
 
   // The default value here is UTF-8 for "\u1234".  (We could also just type
   // the UTF-8 text directly into this text file rather than escape it, but
   // lots of people use editors that would be confused by this.)
-  optional string utf8_string = 6 [default = "\341\210\264"];
+  string utf8_string = 6 [
+    default = "\341\210\264"
+  ];
 
   // Tests for single-precision floating-point values.
-  optional float zero_float = 7 [default = 0];
-  optional float one_float = 8 [default = 1];
-  optional float small_float = 9 [default = 1.5];
-  optional float negative_one_float = 10 [default = -1];
-  optional float negative_float = 11 [default = -1.5];
+  float zero_float = 7 [
+    default = 0
+  ];
+
+  float one_float = 8 [
+    default = 1
+  ];
+
+  float small_float = 9 [
+    default = 1.5
+  ];
+
+  float negative_one_float = 10 [
+    default = -1
+  ];
+
+  float negative_float = 11 [
+    default = -1.5
+  ];
+
   // Using exponents
-  optional float large_float = 12 [default = 2E8];
-  optional float small_negative_float = 13 [default = -8e-28];
+  float large_float = 12 [
+    default = 2e8
+  ];
+
+  float small_negative_float = 13 [
+    default = -8e-28
+  ];
 
   // Text for nonfinite floating-point values.
-  optional double inf_double = 14 [default = inf];
-  optional double neg_inf_double = 15 [default = -inf];
-  optional double nan_double = 16 [default = nan];
-  optional float inf_float = 17 [default = inf];
-  optional float neg_inf_float = 18 [default = -inf];
-  optional float nan_float = 19 [default = nan];
+  double inf_double = 14 [
+    default = inf
+  ];
+
+  double neg_inf_double = 15 [
+    default = -inf
+  ];
+
+  double nan_double = 16 [
+    default = nan
+  ];
+
+  float inf_float = 17 [
+    default = inf
+  ];
+
+  float neg_inf_float = 18 [
+    default = -inf
+  ];
+
+  float nan_float = 19 [
+    default = nan
+  ];
 
   // Tests for C++ trigraphs.
   // Trigraphs should be escaped in C++ generated files, but they should not be
   // escaped for other languages.
   // Note that in .proto file, "\?" is a valid way to escape ? in string
   // literals.
-  optional string cpp_trigraph = 20 [default = "? \? ?? \?? \??? ??/ ?\?-"];
+  string cpp_trigraph = 20 [
+    default = "? \? ?? \?? \??? ??/ ?\?-"
+  ];
 
   // String defaults containing the character '\000'
-  optional string string_with_zero       = 23 [default = "hel\000lo"];
-  optional  bytes bytes_with_zero        = 24 [default = "wor\000ld"];
-  optional string string_piece_with_zero = 25 [ctype=STRING_PIECE,
-                                               default="ab\000c"];
-  optional string cord_with_zero         = 26 [ctype=CORD,
-                                               default="12\0003"];
-  optional string replacement_string     = 27 [default="${unknown}"];
+  string string_with_zero = 23 [
+    default = "hel\000lo"
+  ];
+
+  bytes bytes_with_zero = 24 [
+    default = "wor\000ld"
+  ];
+
+  string string_piece_with_zero = 25 [
+    ctype = STRING_PIECE,
+    default = "ab\000c"
+  ];
+
+  string cord_with_zero = 26 [
+    ctype = CORD,
+    default = "12\0003"
+  ];
+
+  string replacement_string = 27 [
+    default = "${unknown}"
+  ];
 }
 
 message SparseEnumMessage {
-  optional TestSparseEnum sparse_enum = 1;
+  TestSparseEnum sparse_enum = 1;
 }
 
 // Test String and Bytes: string is for valid UTF-8 strings
 message OneString {
-  optional string data = 1;
+  string data = 1;
 }
 
 message MoreString {
@@ -818,7 +1198,7 @@ message MoreString {
 }
 
 message OneBytes {
-  optional bytes data = 1;
+  bytes data = 1;
 }
 
 message MoreBytes {
@@ -826,59 +1206,59 @@ message MoreBytes {
 }
 
 message ManyOptionalString {
-  optional string str1 = 1;
-  optional string str2 = 2;
-  optional string str3 = 3;
-  optional string str4 = 4;
-  optional string str5 = 5;
-  optional string str6 = 6;
-  optional string str7 = 7;
-  optional string str8 = 8;
-  optional string str9 = 9;
-  optional string str10 = 10;
-  optional string str11 = 11;
-  optional string str12 = 12;
-  optional string str13 = 13;
-  optional string str14 = 14;
-  optional string str15 = 15;
-  optional string str16 = 16;
-  optional string str17 = 17;
-  optional string str18 = 18;
-  optional string str19 = 19;
-  optional string str20 = 20;
-  optional string str21 = 21;
-  optional string str22 = 22;
-  optional string str23 = 23;
-  optional string str24 = 24;
-  optional string str25 = 25;
-  optional string str26 = 26;
-  optional string str27 = 27;
-  optional string str28 = 28;
-  optional string str29 = 29;
-  optional string str30 = 30;
-  optional string str31 = 31;
-  optional string str32 = 32;
+  string str1 = 1;
+  string str2 = 2;
+  string str3 = 3;
+  string str4 = 4;
+  string str5 = 5;
+  string str6 = 6;
+  string str7 = 7;
+  string str8 = 8;
+  string str9 = 9;
+  string str10 = 10;
+  string str11 = 11;
+  string str12 = 12;
+  string str13 = 13;
+  string str14 = 14;
+  string str15 = 15;
+  string str16 = 16;
+  string str17 = 17;
+  string str18 = 18;
+  string str19 = 19;
+  string str20 = 20;
+  string str21 = 21;
+  string str22 = 22;
+  string str23 = 23;
+  string str24 = 24;
+  string str25 = 25;
+  string str26 = 26;
+  string str27 = 27;
+  string str28 = 28;
+  string str29 = 29;
+  string str30 = 30;
+  string str31 = 31;
+  string str32 = 32;
 }
 
 // Test int32, uint32, int64, uint64, and bool are all compatible
 message Int32Message {
-  optional int32 data = 1;
+  int32 data = 1;
 }
 
 message Uint32Message {
-  optional uint32 data = 1;
+  uint32 data = 1;
 }
 
 message Int64Message {
-  optional int64 data = 1;
+  int64 data = 1;
 }
 
 message Uint64Message {
-  optional uint64 data = 1;
+  uint64 data = 1;
 }
 
 message BoolMessage {
-  optional bool data = 1;
+  bool data = 1;
 }
 
 // Test oneofs.
@@ -887,60 +1267,120 @@ message TestOneof {
     int32 foo_int = 1;
     string foo_string = 2;
     TestAllTypes foo_message = 3;
-    group FooGroup = 4 {
-      optional int32 a = 5;
-      optional string b = 6;
-    }
+    FooGroup foogroup = 4 [
+      features.message_encoding = DELIMITED
+    ];
+  }
+
+  message FooGroup {
+    int32 a = 5;
+    string b = 6;
   }
 }
 
 message TestOneofBackwardsCompatible {
-  optional int32 foo_int = 1;
-  optional string foo_string = 2;
-  optional TestAllTypes foo_message = 3;
-  optional group FooGroup = 4 {
-    optional int32 a = 5;
-    optional string b = 6;
+  int32 foo_int = 1;
+  string foo_string = 2;
+  TestAllTypes foo_message = 3;
+
+  message FooGroup {
+    int32 a = 5;
+    string b = 6;
   }
+
+  FooGroup foogroup = 4 [
+    features.message_encoding = DELIMITED
+  ];
 }
 
 message TestOneof2 {
   oneof foo {
     int32 foo_int = 1;
     string foo_string = 2;
-    string foo_cord = 3 [ctype=CORD];
-    string foo_string_piece = 4 [ctype=STRING_PIECE];
+    string foo_cord = 3 [
+      ctype = CORD
+    ];
+
+    string foo_string_piece = 4 [
+      ctype = STRING_PIECE
+    ];
+
     bytes foo_bytes = 5;
     NestedEnum foo_enum = 6;
     NestedMessage foo_message = 7;
-    group FooGroup = 8 {
-      optional int32 a = 9;
-      optional string b = 10;
-    }
-    NestedMessage foo_lazy_message = 11 [lazy=true];
-    bytes foo_bytes_cord = 30 [ctype=CORD];
+    FooGroup foogroup = 8 [
+      features.message_encoding = DELIMITED
+    ];
+
+    NestedMessage foo_lazy_message = 11 [
+      lazy = true
+    ];
+
+    bytes foo_bytes_cord = 30 [
+      ctype = CORD
+    ];
+  }
+
+  message FooGroup {
+    int32 a = 9;
+    string b = 10;
   }
 
   oneof bar {
-    int32 bar_int = 12 [default = 5];
-    string bar_string = 13 [default = "STRING"];
-    string bar_cord = 14 [ctype=CORD, default = "CORD"];
-    string bar_string_piece = 15 [ctype=STRING_PIECE, default = "SPIECE"];
-    bytes bar_bytes = 16 [default = "BYTES"];
-    NestedEnum bar_enum = 17 [default = BAR];
-    string bar_string_with_empty_default = 20 [default = ""];
-    string bar_cord_with_empty_default = 21 [ctype=CORD, default = ""];
-    string bar_string_piece_with_empty_default = 22 [ctype=STRING_PIECE, default = ""];
-    bytes bar_bytes_with_empty_default = 23 [default = ""];
+    int32 bar_int = 12 [
+      default = 5
+    ];
+
+    string bar_string = 13 [
+      default = "STRING"
+    ];
+
+    string bar_cord = 14 [
+      ctype = CORD,
+      default = "CORD"
+    ];
+
+    string bar_string_piece = 15 [
+      ctype = STRING_PIECE,
+      default = "SPIECE"
+    ];
+
+    bytes bar_bytes = 16 [
+      default = "BYTES"
+    ];
+
+    NestedEnum bar_enum = 17 [
+      default = BAR
+    ];
+
+    string bar_string_with_empty_default = 20 [
+      default = ""
+    ];
+
+    string bar_cord_with_empty_default = 21 [
+      ctype = CORD,
+      default = ""
+    ];
+
+    string bar_string_piece_with_empty_default = 22 [
+      ctype = STRING_PIECE,
+      default = ""
+    ];
+
+    bytes bar_bytes_with_empty_default = 23 [
+      default = ""
+    ];
   }
 
-  optional int32 baz_int = 18;
-  optional string baz_string = 19 [default = "BAZ"];
+  int32 baz_int = 18;
+  string baz_string = 19 [
+    default = "BAZ"
+  ];
 
   message NestedMessage {
-    optional int64 moo_int = 1;
+    int64 moo_int = 1;
     repeated int32 corge_int = 2;
-    optional NestedMessage child = 3;
+    NestedMessage child = 3;
   }
 
   enum NestedEnum {
@@ -955,49 +1395,95 @@ message TestRequiredOneof {
     int32 foo_int = 1;
     string foo_string = 2;
     NestedMessage foo_message = 3;
-    NestedMessage foo_lazy_message = 4 [lazy = true];
+    NestedMessage foo_lazy_message = 4 [
+      lazy = true
+    ];
   }
+
   message NestedMessage {
-    required double required_double = 1;
+    double required_double = 1 [
+      features.field_presence = LEGACY_REQUIRED
+    ];
   }
 }
 
 // Test messages for packed fields
 
 message TestPackedTypes {
-  repeated    int32 packed_int32    =  90 [packed = true];
-  repeated    int64 packed_int64    =  91 [packed = true];
-  repeated   uint32 packed_uint32   =  92 [packed = true];
-  repeated   uint64 packed_uint64   =  93 [packed = true];
-  repeated   sint32 packed_sint32   =  94 [packed = true];
-  repeated   sint64 packed_sint64   =  95 [packed = true];
-  repeated  fixed32 packed_fixed32  =  96 [packed = true];
-  repeated  fixed64 packed_fixed64  =  97 [packed = true];
-  repeated sfixed32 packed_sfixed32 =  98 [packed = true];
-  repeated sfixed64 packed_sfixed64 =  99 [packed = true];
-  repeated    float packed_float    = 100 [packed = true];
-  repeated   double packed_double   = 101 [packed = true];
-  repeated     bool packed_bool     = 102 [packed = true];
-  repeated ForeignEnum packed_enum  = 103 [packed = true];
+  repeated int32 packed_int32 = 90 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated int64 packed_int64 = 91 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated uint32 packed_uint32 = 92 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated uint64 packed_uint64 = 93 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated sint32 packed_sint32 = 94 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated sint64 packed_sint64 = 95 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated fixed32 packed_fixed32 = 96 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated fixed64 packed_fixed64 = 97 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated sfixed32 packed_sfixed32 = 98 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated sfixed64 packed_sfixed64 = 99 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated float packed_float = 100 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated double packed_double = 101 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated bool packed_bool = 102 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated ForeignEnum packed_enum = 103 [
+    features.repeated_field_encoding = PACKED
+  ];
 }
 
 // A message with the same fields as TestPackedTypes, but without packing. Used
 // to test packed <-> unpacked wire compatibility.
 message TestUnpackedTypes {
-  repeated    int32 unpacked_int32    =  90 [packed = false];
-  repeated    int64 unpacked_int64    =  91 [packed = false];
-  repeated   uint32 unpacked_uint32   =  92 [packed = false];
-  repeated   uint64 unpacked_uint64   =  93 [packed = false];
-  repeated   sint32 unpacked_sint32   =  94 [packed = false];
-  repeated   sint64 unpacked_sint64   =  95 [packed = false];
-  repeated  fixed32 unpacked_fixed32  =  96 [packed = false];
-  repeated  fixed64 unpacked_fixed64  =  97 [packed = false];
-  repeated sfixed32 unpacked_sfixed32 =  98 [packed = false];
-  repeated sfixed64 unpacked_sfixed64 =  99 [packed = false];
-  repeated    float unpacked_float    = 100 [packed = false];
-  repeated   double unpacked_double   = 101 [packed = false];
-  repeated     bool unpacked_bool     = 102 [packed = false];
-  repeated ForeignEnum unpacked_enum  = 103 [packed = false];
+  repeated int32 unpacked_int32 = 90;
+  repeated int64 unpacked_int64 = 91;
+  repeated uint32 unpacked_uint32 = 92;
+  repeated uint64 unpacked_uint64 = 93;
+  repeated sint32 unpacked_sint32 = 94;
+  repeated sint64 unpacked_sint64 = 95;
+  repeated fixed32 unpacked_fixed32 = 96;
+  repeated fixed64 unpacked_fixed64 = 97;
+  repeated sfixed32 unpacked_sfixed32 = 98;
+  repeated sfixed64 unpacked_sfixed64 = 99;
+  repeated float unpacked_float = 100;
+  repeated double unpacked_double = 101;
+  repeated bool unpacked_bool = 102;
+  repeated ForeignEnum unpacked_enum = 103;
 }
 
 message TestPackedExtensions {
@@ -1005,20 +1491,61 @@ message TestPackedExtensions {
 }
 
 extend TestPackedExtensions {
-  repeated    int32 packed_int32_extension    =  90 [packed = true];
-  repeated    int64 packed_int64_extension    =  91 [packed = true];
-  repeated   uint32 packed_uint32_extension   =  92 [packed = true];
-  repeated   uint64 packed_uint64_extension   =  93 [packed = true];
-  repeated   sint32 packed_sint32_extension   =  94 [packed = true];
-  repeated   sint64 packed_sint64_extension   =  95 [packed = true];
-  repeated  fixed32 packed_fixed32_extension  =  96 [packed = true];
-  repeated  fixed64 packed_fixed64_extension  =  97 [packed = true];
-  repeated sfixed32 packed_sfixed32_extension =  98 [packed = true];
-  repeated sfixed64 packed_sfixed64_extension =  99 [packed = true];
-  repeated    float packed_float_extension    = 100 [packed = true];
-  repeated   double packed_double_extension   = 101 [packed = true];
-  repeated     bool packed_bool_extension     = 102 [packed = true];
-  repeated ForeignEnum packed_enum_extension  = 103 [packed = true];
+  repeated int32 packed_int32_extension = 90 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated int64 packed_int64_extension = 91 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated uint32 packed_uint32_extension = 92 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated uint64 packed_uint64_extension = 93 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated sint32 packed_sint32_extension = 94 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated sint64 packed_sint64_extension = 95 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated fixed32 packed_fixed32_extension = 96 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated fixed64 packed_fixed64_extension = 97 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated sfixed32 packed_sfixed32_extension = 98 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated sfixed64 packed_sfixed64_extension = 99 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated float packed_float_extension = 100 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated double packed_double_extension = 101 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated bool packed_bool_extension = 102 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated ForeignEnum packed_enum_extension = 103 [
+    features.repeated_field_encoding = PACKED
+  ];
 }
 
 message TestUnpackedExtensions {
@@ -1026,20 +1553,20 @@ message TestUnpackedExtensions {
 }
 
 extend TestUnpackedExtensions {
-  repeated    int32 unpacked_int32_extension    =  90 [packed = false];
-  repeated    int64 unpacked_int64_extension    =  91 [packed = false];
-  repeated   uint32 unpacked_uint32_extension   =  92 [packed = false];
-  repeated   uint64 unpacked_uint64_extension   =  93 [packed = false];
-  repeated   sint32 unpacked_sint32_extension   =  94 [packed = false];
-  repeated   sint64 unpacked_sint64_extension   =  95 [packed = false];
-  repeated  fixed32 unpacked_fixed32_extension  =  96 [packed = false];
-  repeated  fixed64 unpacked_fixed64_extension  =  97 [packed = false];
-  repeated sfixed32 unpacked_sfixed32_extension =  98 [packed = false];
-  repeated sfixed64 unpacked_sfixed64_extension =  99 [packed = false];
-  repeated    float unpacked_float_extension    = 100 [packed = false];
-  repeated   double unpacked_double_extension   = 101 [packed = false];
-  repeated     bool unpacked_bool_extension     = 102 [packed = false];
-  repeated ForeignEnum unpacked_enum_extension  = 103 [packed = false];
+  repeated int32 unpacked_int32_extension = 90;
+  repeated int64 unpacked_int64_extension = 91;
+  repeated uint32 unpacked_uint32_extension = 92;
+  repeated uint64 unpacked_uint64_extension = 93;
+  repeated sint32 unpacked_sint32_extension = 94;
+  repeated sint64 unpacked_sint64_extension = 95;
+  repeated fixed32 unpacked_fixed32_extension = 96;
+  repeated fixed64 unpacked_fixed64_extension = 97;
+  repeated sfixed32 unpacked_sfixed32_extension = 98;
+  repeated sfixed64 unpacked_sfixed64_extension = 99;
+  repeated float unpacked_float_extension = 100;
+  repeated double unpacked_double_extension = 101;
+  repeated bool unpacked_bool_extension = 102;
+  repeated ForeignEnum unpacked_enum_extension = 103;
 }
 
 // Used by ExtensionSetTest/DynamicExtensions.  The test actually builds
@@ -1051,25 +1578,25 @@ message TestDynamicExtensions {
     DYNAMIC_BAR = 2201;
     DYNAMIC_BAZ = 2202;
   }
+
   message DynamicMessageType {
-    optional int32 dynamic_field = 2100;
+    int32 dynamic_field = 2100;
   }
 
-  optional fixed32 scalar_extension = 2000;
-  optional ForeignEnum enum_extension = 2001;
-  optional DynamicEnumType dynamic_enum_extension = 2002;
-
-  optional ForeignMessage message_extension = 2003;
-  optional DynamicMessageType dynamic_message_extension = 2004;
-
+  fixed32 scalar_extension = 2000;
+  ForeignEnum enum_extension = 2001;
+  DynamicEnumType dynamic_enum_extension = 2002;
+  ForeignMessage message_extension = 2003;
+  DynamicMessageType dynamic_message_extension = 2004;
   repeated string repeated_extension = 2005;
-  repeated sint32 packed_extension = 2006 [packed = true];
+  repeated sint32 packed_extension = 2006 [
+    features.repeated_field_encoding = PACKED
+  ];
 }
 
 message TestRepeatedString {
   repeated string repeated_string1 = 1;
   repeated string repeated_string2 = 2;
-
   repeated bytes repeated_bytes11 = 11;
   repeated bytes repeated_bytes12 = 12;
 }
@@ -1079,16 +1606,17 @@ message TestRepeatedScalarDifferentTagSizes {
   // used in order to get a tag of the right size; all of the repeated fields
   // in TestAllTypes didn't trigger the check.
   repeated fixed32 repeated_fixed32 = 12;
+
   // Check for a varint type, just for good measure.
-  repeated int32   repeated_int32   = 13;
+  repeated int32 repeated_int32 = 13;
 
   // These have two-byte tags.
   repeated fixed64 repeated_fixed64 = 2046;
-  repeated int64   repeated_int64   = 2047;
+  repeated int64 repeated_int64 = 2047;
 
   // Three byte tags.
-  repeated float   repeated_float   = 262142;
-  repeated uint64  repeated_uint64  = 262143;
+  repeated float repeated_float = 262142;
+  repeated uint64 repeated_uint64 = 262143;
 }
 
 // Test that if an optional or required message/group field appears multiple
@@ -1103,27 +1631,54 @@ message TestParsingMerge {
     repeated TestAllTypes field1 = 1;
     repeated TestAllTypes field2 = 2;
     repeated TestAllTypes field3 = 3;
-    repeated group Group1 = 10 {
-      optional TestAllTypes field1 = 11;
+
+    message Group1 {
+      TestAllTypes field1 = 11;
     }
-    repeated group Group2 = 20 {
-      optional TestAllTypes field1 = 21;
+
+    repeated Group1 group1 = 10 [
+      features.message_encoding = DELIMITED
+    ];
+
+    message Group2 {
+      TestAllTypes field1 = 21;
     }
+
+    repeated Group2 group2 = 20 [
+      features.message_encoding = DELIMITED
+    ];
+
     repeated TestAllTypes ext1 = 1000;
     repeated TestAllTypes ext2 = 1001;
   }
-  required TestAllTypes required_all_types = 1;
-  optional TestAllTypes optional_all_types = 2;
+
+  TestAllTypes required_all_types = 1 [
+    features.field_presence = LEGACY_REQUIRED
+  ];
+
+  TestAllTypes optional_all_types = 2;
   repeated TestAllTypes repeated_all_types = 3;
-  optional group OptionalGroup = 10 {
-    optional TestAllTypes optional_group_all_types = 11;
+
+  message OptionalGroup {
+    TestAllTypes optional_group_all_types = 11;
   }
-  repeated group RepeatedGroup = 20 {
-    optional TestAllTypes repeated_group_all_types = 21;
+
+  OptionalGroup optionalgroup = 10 [
+    features.message_encoding = DELIMITED
+  ];
+
+  message RepeatedGroup {
+    TestAllTypes repeated_group_all_types = 21;
   }
+
+  repeated RepeatedGroup repeatedgroup = 20 [
+    features.message_encoding = DELIMITED
+  ];
+
   extensions 1000 to max;
+
   extend TestParsingMerge {
-    optional TestAllTypes optional_ext = 1000;
+    TestAllTypes optional_ext = 1000;
     repeated TestAllTypes repeated_ext = 1001;
   }
 }
@@ -1131,65 +1686,104 @@ message TestParsingMerge {
 // Test that the correct exception is thrown by parseFrom in a corner case
 // involving merging, extensions, and required fields.
 message TestMergeException {
-  optional TestAllExtensions all_extensions = 1;
+  TestAllExtensions all_extensions = 1;
 }
 
 message TestCommentInjectionMessage {
   // */ <- This should not close the generated doc comment
-  optional string a = 1 [default="*/ <- Neither should this."];
+  string a = 1 [
+    default = "*/ <- Neither should this."
+  ];
 }
 
 // Used to check that the c++ code generator re-orders messages to reduce
 // padding.
 message TestMessageSize {
-  optional bool m1 = 1;
-  optional int64 m2 = 2;
-  optional bool m3 = 3;
-  optional string m4 = 4;
-  optional int32 m5 = 5;
-  optional int64 m6 = 6;
+  bool m1 = 1;
+  int64 m2 = 2;
+  bool m3 = 3;
+  string m4 = 4;
+  int32 m5 = 5;
+  int64 m6 = 6;
+}
+
+message OpenEnumMessage {
+  enum TestEnum {
+    option features.enum_type = OPEN;
+
+    UNKNOWN = 0;
+    FOO = 1;
+    BAR = 2;
+    BAZ = 3;
+  }
+
+  TestEnum opt_open = 1;
+
+  ForeignEnum opt_closed = 2;
+  repeated TestEnum repeated_open = 3;
+
+  repeated ForeignEnum repeated_closed = 4;
 }
 
 // Test that RPC services work.
-message FooRequest  {}
-message FooResponse {}
+message FooRequest {
+}
 
-message FooClientMessage {}
-message FooServerMessage{}
+message FooResponse {
+}
+
+message FooClientMessage {
+}
+
+message FooServerMessage {
+}
 
 service TestService {
   rpc Foo(FooRequest) returns (FooResponse);
+
   rpc Bar(BarRequest) returns (BarResponse);
 }
 
-message BarRequest  {}
-message BarResponse {}
+message BarRequest {
+}
+
+message BarResponse {
+}
 
 message TestJsonName {
-  optional int32 field_name1 = 1;
-  optional int32 fieldName2 = 2;
-  optional int32 FieldName3 = 3;
-  optional int32 _field_name4 = 4;
-  optional int32 FIELD_NAME5 = 5;
-  optional int32 field_name6 = 6 [json_name = "@type"];
-  optional int32 fieldname7 = 7;
+  int32 field_name1 = 1;
+  int32 fieldName2 = 2;
+  int32 FieldName3 = 3;
+  int32 _field_name4 = 4;
+  int32 FIELD_NAME5 = 5;
+  int32 field_name6 = 6 [
+    json_name = "@type"
+  ];
+
+  int32 fieldname7 = 7;
 }
 
 message TestHugeFieldNumbers {
-  optional int32 optional_int32 = 536870000;
-  optional int32 fixed_32 = 536870001;
-  repeated int32 repeated_int32 = 536870002 [packed = false];
-  repeated int32 packed_int32 = 536870003 [packed = true];
-
-  optional ForeignEnum optional_enum = 536870004;
-  optional string optional_string = 536870005;
-  optional bytes optional_bytes = 536870006;
-  optional ForeignMessage optional_message = 536870007;
-
-  optional group OptionalGroup = 536870008 {
-    optional int32 group_a = 536870009;
+  int32 optional_int32 = 536870000;
+  int32 fixed_32 = 536870001;
+  repeated int32 repeated_int32 = 536870002;
+  repeated int32 packed_int32 = 536870003 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  ForeignEnum optional_enum = 536870004;
+  string optional_string = 536870005;
+  bytes optional_bytes = 536870006;
+  ForeignMessage optional_message = 536870007;
+
+  message OptionalGroup {
+    int32 group_a = 536870009;
   }
 
+  OptionalGroup optionalgroup = 536870008 [
+    features.message_encoding = DELIMITED
+  ];
+
   map<string, string> string_string_map = 536870010;
 
   oneof oneof_field {
@@ -1199,63 +1793,82 @@ message TestHugeFieldNumbers {
     bytes oneof_bytes = 536870014;
   }
 
-  extensions 536860000 to 536869999 [declaration = {
-    number: 536860000
-    full_name: ".protobuf_unittest.test_all_types"
-    type: ".protobuf_unittest.TestAllTypes"
-  }];
+  extensions 536860000 to 536869999 [
+    declaration = {
+      number: 536860000
+      full_name: ".protobuf_unittest.test_all_types"
+      type: ".protobuf_unittest.TestAllTypes"
+    }
+  ];
 }
 
 extend TestHugeFieldNumbers {
-  optional TestAllTypes test_all_types = 536860000;
+  TestAllTypes test_all_types = 536860000;
 }
 
 message TestExtensionInsideTable {
-  optional int32 field1 = 1;
-  optional int32 field2 = 2;
-  optional int32 field3 = 3;
-  optional int32 field4 = 4;
-  extensions 5 to 5;
-  optional int32 field6 = 6;
-  optional int32 field7 = 7;
-  optional int32 field8 = 8;
-  optional int32 field9 = 9;
-  optional int32 field10 = 10;
+  int32 field1 = 1;
+  int32 field2 = 2;
+  int32 field3 = 3;
+  int32 field4 = 4;
+
+  extensions 5;
+
+  int32 field6 = 6;
+  int32 field7 = 7;
+  int32 field8 = 8;
+  int32 field9 = 9;
+  int32 field10 = 10;
 }
 
 extend TestExtensionInsideTable {
-  optional int32 test_extension_inside_table_extension = 5;
+  int32 test_extension_inside_table_extension = 5;
 }
 
 // NOTE: Intentionally nested to mirror go/glep.
 message TestNestedGroupExtensionOuter {
-  optional group Layer1OptionalGroup = 1 {
-    repeated group Layer2RepeatedGroup = 2 {
+  message Layer1OptionalGroup {
+    message Layer2RepeatedGroup {
       extensions 3
-        // NOTE: extension metadata is not supported due to targets such as
-        // `//google/protobuf_legacy_opensource/src:shell_scripts_test`,
-        // eee https://screenshot.googleplex.com/Axz2QD8nxjdpyFF
-        //[metadata = {
-        // NOTE: can't write type there due to some clever build gen code at
-        // http://google3/google/protobuf/BUILD;l=1247;rcl=411090862
-        // type: "protobuf_unittest.TestNestedGroupExtensionInnerExtension",
-        // name: "inner",
-        // }]
-        ;
-      optional string another_field = 6;
+      //  NOTE: extension metadata is not supported due to targets such as
+      //  `//google/protobuf_legacy_opensource/src:shell_scripts_test`,
+      //  eee https://screenshot.googleplex.com/Axz2QD8nxjdpyFF
+      // [metadata = {
+      //  NOTE: can't write type there due to some clever build gen code at
+      //  http://google3/google/protobuf/BUILD;l=1247;rcl=411090862
+      //  type: "protobuf_unittest.TestNestedGroupExtensionInnerExtension",
+      //  name: "inner",
+      //  }]
+      ;
+
+      string another_field = 6;
     }
-    repeated group Layer2AnotherOptionalRepeatedGroup = 4 {
-      optional string but_why_tho = 5;
+
+    repeated Layer2RepeatedGroup layer2repeatedgroup = 2 [
+      features.message_encoding = DELIMITED
+    ];
+
+    message Layer2AnotherOptionalRepeatedGroup {
+      string but_why_tho = 5;
     }
+
+    repeated Layer2AnotherOptionalRepeatedGroup
+        layer2anotheroptionalrepeatedgroup = 4 [
+          features.message_encoding = DELIMITED
+        ];
   }
+
+  Layer1OptionalGroup layer1optionalgroup = 1 [
+    features.message_encoding = DELIMITED
+  ];
 }
 
 message TestNestedGroupExtensionInnerExtension {
-  optional string inner_name= 1;
+  string inner_name = 1;
 }
 
 extend TestNestedGroupExtensionOuter.Layer1OptionalGroup.Layer2RepeatedGroup {
-  optional TestNestedGroupExtensionInnerExtension inner = 3;
+  TestNestedGroupExtensionInnerExtension inner = 3;
 }
 
 enum VeryLargeEnum {
@@ -1360,163 +1973,147 @@ enum VeryLargeEnum {
   ENUM_LABEL_98 = 98;
   ENUM_LABEL_99 = 99;
   ENUM_LABEL_100 = 100;
-};
+}
 
 message TestExtensionRangeSerialize {
-  optional int32 foo_one = 1;
+  int32 foo_one = 1;
 
-  extensions 2 to 2;
+  extensions 2;
   extensions 3 to 4;
 
-  optional int32 foo_two = 6;
-  optional int32 foo_three = 7;
+  int32 foo_two = 6;
+  int32 foo_three = 7;
 
   extensions 9 to 10;
 
-  optional int32 foo_four = 13;
+  int32 foo_four = 13;
 
   extensions 15 to 15;
   extensions 17 to 17;
   extensions 19 to 19;
 
   extend TestExtensionRangeSerialize {
-    optional int32 bar_one = 2;
-    optional int32 bar_two = 4;
-
-    optional int32 bar_three = 10;
-
-    optional int32 bar_four = 15;
-    optional int32 bar_five = 19;
+    int32 bar_one = 2;
+    int32 bar_two = 4;
+    int32 bar_three = 10;
+    int32 bar_four = 15;
+    int32 bar_five = 19;
   }
 }
 
 message TestVerifyInt32Simple {
-    optional int32 optional_int32_1 = 1;
-    optional int32 optional_int32_2 = 2;
-    optional int32 optional_int32_63 = 63;
-    optional int32 optional_int32_64 = 64;
+  int32 optional_int32_1 = 1;
+  int32 optional_int32_2 = 2;
+  int32 optional_int32_63 = 63;
+  int32 optional_int32_64 = 64;
 }
 
 message TestVerifyInt32 {
-    optional int32 optional_int32_1 = 1;
-    optional int32 optional_int32_2 = 2;
-    optional int32 optional_int32_63 = 63;
-    optional int32 optional_int32_64 = 64;
-
-    optional TestAllTypes optional_all_types = 9;
-    repeated TestAllTypes repeated_all_types = 10;
+  int32 optional_int32_1 = 1;
+  int32 optional_int32_2 = 2;
+  int32 optional_int32_63 = 63;
+  int32 optional_int32_64 = 64;
+  TestAllTypes optional_all_types = 9;
+  repeated TestAllTypes repeated_all_types = 10;
 }
 
 message TestVerifyMostlyInt32 {
-    optional int64 optional_int64_30 = 30;
-
-    optional int32 optional_int32_1 = 1;
-    optional int32 optional_int32_2 = 2;
-    optional int32 optional_int32_3 = 3;
-    optional int32 optional_int32_4 = 4;
-    optional int32 optional_int32_63 = 63;
-    optional int32 optional_int32_64 = 64;
-
-    optional TestAllTypes optional_all_types = 9;
-    repeated TestAllTypes repeated_all_types = 10;
+  int64 optional_int64_30 = 30;
+  int32 optional_int32_1 = 1;
+  int32 optional_int32_2 = 2;
+  int32 optional_int32_3 = 3;
+  int32 optional_int32_4 = 4;
+  int32 optional_int32_63 = 63;
+  int32 optional_int32_64 = 64;
+  TestAllTypes optional_all_types = 9;
+  repeated TestAllTypes repeated_all_types = 10;
 }
 
 message TestVerifyMostlyInt32BigFieldNumber {
-    optional int64 optional_int64_30 = 30;
-    optional int32 optional_int32_300 = 300;
-
-    optional int32 optional_int32_1 = 1;
-    optional int32 optional_int32_2 = 2;
-    optional int32 optional_int32_3 = 3;
-    optional int32 optional_int32_4 = 4;
-    optional int32 optional_int32_63 = 63;
-    optional int32 optional_int32_64 = 64;
-
-    optional TestAllTypes optional_all_types = 9;
-    repeated TestAllTypes repeated_all_types = 10;
+  int64 optional_int64_30 = 30;
+  int32 optional_int32_300 = 300;
+  int32 optional_int32_1 = 1;
+  int32 optional_int32_2 = 2;
+  int32 optional_int32_3 = 3;
+  int32 optional_int32_4 = 4;
+  int32 optional_int32_63 = 63;
+  int32 optional_int32_64 = 64;
+  TestAllTypes optional_all_types = 9;
+  repeated TestAllTypes repeated_all_types = 10;
 }
 
 message TestVerifyUint32Simple {
-    optional uint32 optional_uint32_1 = 1;
-    optional uint32 optional_uint32_2 = 2;
-    optional uint32 optional_uint32_63 = 63;
-    optional uint32 optional_uint32_64 = 64;
+  uint32 optional_uint32_1 = 1;
+  uint32 optional_uint32_2 = 2;
+  uint32 optional_uint32_63 = 63;
+  uint32 optional_uint32_64 = 64;
 }
 
 message TestVerifyUint32 {
-    optional uint32 optional_uint32_1 = 1;
-    optional uint32 optional_uint32_2 = 2;
-    optional uint32 optional_uint32_63 = 63;
-    optional uint32 optional_uint32_64 = 64;
-
-    optional TestAllTypes optional_all_types = 9;
-    repeated TestAllTypes repeated_all_types = 10;
+  uint32 optional_uint32_1 = 1;
+  uint32 optional_uint32_2 = 2;
+  uint32 optional_uint32_63 = 63;
+  uint32 optional_uint32_64 = 64;
+  TestAllTypes optional_all_types = 9;
+  repeated TestAllTypes repeated_all_types = 10;
 }
 
 message TestVerifyOneUint32 {
-    optional uint32 optional_uint32_1 = 1;
-    optional int32 optional_int32_2 = 2;
-    optional int32 optional_int32_63 = 63;
-    optional int32 optional_int32_64 = 64;
-
-    optional TestAllTypes optional_all_types = 9;
-    repeated TestAllTypes repeated_all_types = 10;
+  uint32 optional_uint32_1 = 1;
+  int32 optional_int32_2 = 2;
+  int32 optional_int32_63 = 63;
+  int32 optional_int32_64 = 64;
+  TestAllTypes optional_all_types = 9;
+  repeated TestAllTypes repeated_all_types = 10;
 }
 
 message TestVerifyOneInt32BigFieldNumber {
-    optional int32 optional_int32_65 = 65;
-
-    optional int64 optional_int64_1 = 1;
-    optional int64 optional_int64_2 = 2;
-    optional int64 optional_int64_63 = 63;
-    optional int64 optional_int64_64 = 64;
-
-    optional TestAllTypes optional_all_types = 9;
-    repeated TestAllTypes repeated_all_types = 10;
+  int32 optional_int32_65 = 65;
+  int64 optional_int64_1 = 1;
+  int64 optional_int64_2 = 2;
+  int64 optional_int64_63 = 63;
+  int64 optional_int64_64 = 64;
+  TestAllTypes optional_all_types = 9;
+  repeated TestAllTypes repeated_all_types = 10;
 }
 
 message TestVerifyInt32BigFieldNumber {
-    optional int32 optional_int32_1000 = 1000;
-    optional int32 optional_int32_65 = 65;
-
-    optional int32 optional_int32_1 = 1;
-    optional int32 optional_int32_2 = 2;
-    optional int32 optional_int32_63 = 63;
-    optional int32 optional_int32_64 = 64;
-
-    optional TestAllTypes optional_all_types = 9;
-    repeated TestAllTypes repeated_all_types = 10;
+  int32 optional_int32_1000 = 1000;
+  int32 optional_int32_65 = 65;
+  int32 optional_int32_1 = 1;
+  int32 optional_int32_2 = 2;
+  int32 optional_int32_63 = 63;
+  int32 optional_int32_64 = 64;
+  TestAllTypes optional_all_types = 9;
+  repeated TestAllTypes repeated_all_types = 10;
 }
 
 message TestVerifyUint32BigFieldNumber {
-    optional uint32 optional_uint32_1000 = 1000;
-    optional uint32 optional_uint32_65 = 65;
-
-    optional uint32 optional_uint32_1 = 1;
-    optional uint32 optional_uint32_2 = 2;
-    optional uint32 optional_uint32_63 = 63;
-    optional uint32 optional_uint32_64 = 64;
-
-    optional TestAllTypes optional_all_types = 9;
-    repeated TestAllTypes repeated_all_types = 10;
+  uint32 optional_uint32_1000 = 1000;
+  uint32 optional_uint32_65 = 65;
+  uint32 optional_uint32_1 = 1;
+  uint32 optional_uint32_2 = 2;
+  uint32 optional_uint32_63 = 63;
+  uint32 optional_uint32_64 = 64;
+  TestAllTypes optional_all_types = 9;
+  repeated TestAllTypes repeated_all_types = 10;
 }
 
 message TestVerifyBigFieldNumberUint32 {
   message Nested {
-    optional uint32 optional_uint32_5000 = 5000;
-    optional uint32 optional_uint32_1000 = 1000;
-    optional uint32 optional_uint32_66 = 66;
-    optional uint32 optional_uint32_65 = 65;
-
-    optional uint32 optional_uint32_1 = 1;
-    optional uint32 optional_uint32_2 = 2;
-    optional uint32 optional_uint32_63 = 63;
-    optional uint32 optional_uint32_64 = 64;
-
-    optional Nested optional_nested = 9;
+    uint32 optional_uint32_5000 = 5000;
+    uint32 optional_uint32_1000 = 1000;
+    uint32 optional_uint32_66 = 66;
+    uint32 optional_uint32_65 = 65;
+    uint32 optional_uint32_1 = 1;
+    uint32 optional_uint32_2 = 2;
+    uint32 optional_uint32_63 = 63;
+    uint32 optional_uint32_64 = 64;
+    Nested optional_nested = 9;
     repeated Nested repeated_nested = 10;
   }
-  optional Nested optional_nested = 1;
+
+  Nested optional_nested = 1;
 }
 
 // This message contains different kind of enums to exercise the different
@@ -1526,31 +2123,49 @@ message EnumParseTester {
     SEQ_SMALL_0_DEFAULT = 0;
     SEQ_SMALL_0_1 = 1;
     SEQ_SMALL_0_2 = 2;
-  };
-  optional SeqSmall0 optional_seq_small_0_lowfield = 1;
-  optional SeqSmall0 optional_seq_small_0_midfield = 1001;
-  optional SeqSmall0 optional_seq_small_0_hifield = 1000001;
+  }
+
+  SeqSmall0 optional_seq_small_0_lowfield = 1;
+  SeqSmall0 optional_seq_small_0_midfield = 1001;
+  SeqSmall0 optional_seq_small_0_hifield = 1000001;
   repeated SeqSmall0 repeated_seq_small_0_lowfield = 2;
   repeated SeqSmall0 repeated_seq_small_0_midfield = 1002;
   repeated SeqSmall0 repeated_seq_small_0_hifield = 1000002;
-  repeated SeqSmall0 packed_seq_small_0_lowfield = 3 [packed = true];
-  repeated SeqSmall0 packed_seq_small_0_midfield = 1003 [packed = true];
-  repeated SeqSmall0 packed_seq_small_0_hifield = 1000003 [packed = true];
+  repeated SeqSmall0 packed_seq_small_0_lowfield = 3 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated SeqSmall0 packed_seq_small_0_midfield = 1003 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated SeqSmall0 packed_seq_small_0_hifield = 1000003 [
+    features.repeated_field_encoding = PACKED
+  ];
 
   enum SeqSmall1 {
     SEQ_SMALL_1_DEFAULT = 1;
     SEQ_SMALL_1_2 = 2;
     SEQ_SMALL_1_3 = 3;
-  };
-  optional SeqSmall1 optional_seq_small_1_lowfield = 4;
-  optional SeqSmall1 optional_seq_small_1_midfield = 1004;
-  optional SeqSmall1 optional_seq_small_1_hifield = 1000004;
+  }
+
+  SeqSmall1 optional_seq_small_1_lowfield = 4;
+  SeqSmall1 optional_seq_small_1_midfield = 1004;
+  SeqSmall1 optional_seq_small_1_hifield = 1000004;
   repeated SeqSmall1 repeated_seq_small_1_lowfield = 5;
   repeated SeqSmall1 repeated_seq_small_1_midfield = 1005;
   repeated SeqSmall1 repeated_seq_small_1_hifield = 1000005;
-  repeated SeqSmall1 packed_seq_small_1_lowfield = 6 [packed = true];
-  repeated SeqSmall1 packed_seq_small_1_midfield = 1006 [packed = true];
-  repeated SeqSmall1 packed_seq_small_1_hifield = 1000006 [packed = true];
+  repeated SeqSmall1 packed_seq_small_1_lowfield = 6 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated SeqSmall1 packed_seq_small_1_midfield = 1006 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated SeqSmall1 packed_seq_small_1_hifield = 1000006 [
+    features.repeated_field_encoding = PACKED
+  ];
 
   enum SeqLarge {
     SEQ_LARGE_DEFAULT = -1;
@@ -1588,16 +2203,25 @@ message EnumParseTester {
     SEQ_LARGE_31 = 31;
     SEQ_LARGE_32 = 32;
     SEQ_LARGE_33 = 33;
-  };
-  optional SeqLarge optional_seq_large_lowfield = 7;
-  optional SeqLarge optional_seq_large_midfield = 1007;
-  optional SeqLarge optional_seq_large_hifield = 1000007;
+  }
+
+  SeqLarge optional_seq_large_lowfield = 7;
+  SeqLarge optional_seq_large_midfield = 1007;
+  SeqLarge optional_seq_large_hifield = 1000007;
   repeated SeqLarge repeated_seq_large_lowfield = 8;
   repeated SeqLarge repeated_seq_large_midfield = 1008;
   repeated SeqLarge repeated_seq_large_hifield = 1000008;
-  repeated SeqLarge packed_seq_large_lowfield = 9 [packed = true];
-  repeated SeqLarge packed_seq_large_midfield = 1009 [packed = true];
-  repeated SeqLarge packed_seq_large_hifield = 1000009 [packed = true];
+  repeated SeqLarge packed_seq_large_lowfield = 9 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated SeqLarge packed_seq_large_midfield = 1009 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated SeqLarge packed_seq_large_hifield = 1000009 [
+    features.repeated_field_encoding = PACKED
+  ];
 
   enum Arbitrary {
     ARBITRARY_DEFAULT = -123123;
@@ -1606,156 +2230,232 @@ message EnumParseTester {
     ARBITRARY_3 = 213213;
     ARBITRARY_MIN = -2147483648;
     ARBITRARY_MAX = 2147483647;
-  };
-  optional Arbitrary optional_arbitrary_lowfield = 10;
-  optional Arbitrary optional_arbitrary_midfield = 1010;
-  optional Arbitrary optional_arbitrary_hifield = 1000010;
+  }
+
+  Arbitrary optional_arbitrary_lowfield = 10;
+  Arbitrary optional_arbitrary_midfield = 1010;
+  Arbitrary optional_arbitrary_hifield = 1000010;
   repeated Arbitrary repeated_arbitrary_lowfield = 11;
   repeated Arbitrary repeated_arbitrary_midfield = 1011;
   repeated Arbitrary repeated_arbitrary_hifield = 1000011;
-  repeated Arbitrary packed_arbitrary_lowfield = 12 [packed = true];
-  repeated Arbitrary packed_arbitrary_midfield = 1012 [packed = true];
-  repeated Arbitrary packed_arbitrary_hifield = 1000012 [packed = true];
+  repeated Arbitrary packed_arbitrary_lowfield = 12 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated Arbitrary packed_arbitrary_midfield = 1012 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated Arbitrary packed_arbitrary_hifield = 1000012 [
+    features.repeated_field_encoding = PACKED
+  ];
 
   extensions 2000000 to max;
+
   extend EnumParseTester {
-    optional Arbitrary optional_arbitrary_ext = 2000000;
+    Arbitrary optional_arbitrary_ext = 2000000;
     repeated Arbitrary repeated_arbitrary_ext = 2000001;
-    repeated Arbitrary packed_arbitrary_ext = 2000002 [packed = true];
+    repeated Arbitrary packed_arbitrary_ext = 2000002 [
+      features.repeated_field_encoding = PACKED
+    ];
   }
 
   // An arbitrary field we can append to to break the runs of repeated fields.
-  optional int32 other_field = 99;
+  int32 other_field = 99;
 }
 
 // This message contains different kind of bool fields to exercise the different
 // parsers in table-drived.
 message BoolParseTester {
-  optional bool optional_bool_lowfield = 1;
-  optional bool optional_bool_midfield = 1001;
-  optional bool optional_bool_hifield = 1000001;
+  bool optional_bool_lowfield = 1;
+  bool optional_bool_midfield = 1001;
+  bool optional_bool_hifield = 1000001;
   repeated bool repeated_bool_lowfield = 2;
   repeated bool repeated_bool_midfield = 1002;
   repeated bool repeated_bool_hifield = 1000002;
-  repeated bool packed_bool_lowfield = 3 [packed = true];
-  repeated bool packed_bool_midfield = 1003 [packed = true];
-  repeated bool packed_bool_hifield = 1000003 [packed = true];
+  repeated bool packed_bool_lowfield = 3 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated bool packed_bool_midfield = 1003 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated bool packed_bool_hifield = 1000003 [
+    features.repeated_field_encoding = PACKED
+  ];
 
   extensions 2000000 to max;
+
   extend BoolParseTester {
-    optional bool optional_bool_ext = 2000000;
+    bool optional_bool_ext = 2000000;
     repeated bool repeated_bool_ext = 2000001;
-    repeated bool packed_bool_ext = 2000002 [packed = true];
+    repeated bool packed_bool_ext = 2000002 [
+      features.repeated_field_encoding = PACKED
+    ];
   }
 
   // An arbitrary field we can append to to break the runs of repeated fields.
-  optional int32 other_field = 99;
+  int32 other_field = 99;
 }
 
 message Int32ParseTester {
-  optional int32 optional_int32_lowfield = 1;
-  optional int32 optional_int32_midfield = 1001;
-  optional int32 optional_int32_hifield = 1000001;
+  int32 optional_int32_lowfield = 1;
+  int32 optional_int32_midfield = 1001;
+  int32 optional_int32_hifield = 1000001;
   repeated int32 repeated_int32_lowfield = 2;
   repeated int32 repeated_int32_midfield = 1002;
   repeated int32 repeated_int32_hifield = 1000002;
-  repeated int32 packed_int32_lowfield = 3 [packed = true];
-  repeated int32 packed_int32_midfield = 1003 [packed = true];
-  repeated int32 packed_int32_hifield = 1000003 [packed = true];
+  repeated int32 packed_int32_lowfield = 3 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated int32 packed_int32_midfield = 1003 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated int32 packed_int32_hifield = 1000003 [
+    features.repeated_field_encoding = PACKED
+  ];
 
   extensions 2000000 to max;
+
   extend Int32ParseTester {
-    optional int32 optional_int32_ext = 2000000;
+    int32 optional_int32_ext = 2000000;
     repeated int32 repeated_int32_ext = 2000001;
-    repeated int32 packed_int32_ext = 2000002 [packed = true];
+    repeated int32 packed_int32_ext = 2000002 [
+      features.repeated_field_encoding = PACKED
+    ];
   }
 
   // An arbitrary field we can append to to break the runs of repeated fields.
-  optional int32 other_field = 99;
+  int32 other_field = 99;
 }
 
 message Int64ParseTester {
-  optional int64 optional_int64_lowfield = 1;
-  optional int64 optional_int64_midfield = 1001;
-  optional int64 optional_int64_hifield = 1000001;
+  int64 optional_int64_lowfield = 1;
+  int64 optional_int64_midfield = 1001;
+  int64 optional_int64_hifield = 1000001;
   repeated int64 repeated_int64_lowfield = 2;
   repeated int64 repeated_int64_midfield = 1002;
   repeated int64 repeated_int64_hifield = 1000002;
-  repeated int64 packed_int64_lowfield = 3 [packed = true];
-  repeated int64 packed_int64_midfield = 1003 [packed = true];
-  repeated int64 packed_int64_hifield = 1000003 [packed = true];
+  repeated int64 packed_int64_lowfield = 3 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated int64 packed_int64_midfield = 1003 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  repeated int64 packed_int64_hifield = 1000003 [
+    features.repeated_field_encoding = PACKED
+  ];
 
   extensions 2000000 to max;
+
   extend Int64ParseTester {
-    optional int64 optional_int64_ext = 2000000;
+    int64 optional_int64_ext = 2000000;
     repeated int64 repeated_int64_ext = 2000001;
-    repeated int64 packed_int64_ext = 2000002 [packed = true];
+    repeated int64 packed_int64_ext = 2000002 [
+      features.repeated_field_encoding = PACKED
+    ];
   }
 
   // An arbitrary field we can append to to break the runs of repeated fields.
-  optional int32 other_field = 99;
+  int32 other_field = 99;
 }
 
 message InlinedStringIdxRegressionProto {
   // We mix data to make sure aux ids and inlined string idx do not match.
   // aux_idx == inlined_string_idx == 1
-  optional string str1 = 1;
+  string str1 = 1;
+
   // aux_idx == 2
-  optional InlinedStringIdxRegressionProto sub = 2;
+  InlinedStringIdxRegressionProto sub = 2;
+
   // aux_idx == 3, inlined_string_idx == 2
-  optional string str2 = 3;
+  string str2 = 3;
+
   // aux_idx == 4, inlined_string_idx == 3
-  optional bytes str3 = 4;
+  bytes str3 = 4;
 }
 
 message StringParseTester {
-  optional string optional_string_lowfield = 1;
-  optional string optional_string_midfield = 1001;
-  optional string optional_string_hifield = 1000001;
+  string optional_string_lowfield = 1;
+  string optional_string_midfield = 1001;
+  string optional_string_hifield = 1000001;
   repeated string repeated_string_lowfield = 2;
   repeated string repeated_string_midfield = 1002;
   repeated string repeated_string_hifield = 1000002;
 
   extensions 2000000 to max;
+
   extend StringParseTester {
-    optional string optional_string_ext = 2000000;
+    string optional_string_ext = 2000000;
     repeated string repeated_string_ext = 2000001;
   }
 }
 
-message BadFieldNames{
-  optional int32 OptionalInt32 = 1;
-  optional int32 for = 2;
+message BadFieldNames {
+  int32 OptionalInt32 = 1;
+  int32 for = 2;
 }
 
 message TestNestedMessageRedaction {
-  optional string optional_unredacted_nested_string = 1;
-  optional string optional_redacted_nested_string = 2 [debug_redact = true];
+  string optional_unredacted_nested_string = 1;
+  string optional_redacted_nested_string = 2 [
+    debug_redact = true
+  ];
 }
 
 message RedactedFields {
-  optional string optional_redacted_string = 1 [debug_redact = true];
-  optional string optional_unredacted_string = 2;
-  repeated string repeated_redacted_string = 3 [debug_redact = true];
+  string optional_redacted_string = 1 [
+    debug_redact = true
+  ];
+
+  string optional_unredacted_string = 2;
+  repeated string repeated_redacted_string = 3 [
+    debug_redact = true
+  ];
+
   repeated string repeated_unredacted_string = 4;
-  optional TestNestedMessageRedaction optional_redacted_message = 5 [debug_redact = true];
-  optional TestNestedMessageRedaction optional_unredacted_message = 6;
-  repeated TestNestedMessageRedaction repeated_redacted_message = 7
-      [debug_redact = true];
+  TestNestedMessageRedaction optional_redacted_message = 5 [
+    debug_redact = true
+  ];
+
+  TestNestedMessageRedaction optional_unredacted_message = 6;
+  repeated TestNestedMessageRedaction repeated_redacted_message = 7 [
+    debug_redact = true
+  ];
+
   repeated TestNestedMessageRedaction repeated_unredacted_message = 8;
-  map<string, string> map_redacted_string = 9 [debug_redact = true];
+  map<string, string> map_redacted_string = 9 [
+    debug_redact = true
+  ];
+
   map<string, string> map_unredacted_string = 10;
-  optional string optional_redacted_false_string = 11 [debug_redact = false];
+  string optional_redacted_false_string = 11 [
+    debug_redact = false
+  ];
+
   extensions 20 to 30;
 }
 
 extend RedactedFields {
-  optional string redacted_extension = 20 [debug_redact = true];
+  string redacted_extension = 20 [
+    debug_redact = true
+  ];
 }
 
-message TestCord{
-  optional bytes optional_bytes_cord = 1 [ctype=CORD];
-  optional bytes optional_bytes_cord_default = 2 [ctype=CORD, default = "hello"];
+message TestCord {
+  bytes optional_bytes_cord = 1 [
+    ctype = CORD
+  ];
+
+  bytes optional_bytes_cord_default = 2 [
+    ctype = CORD,
+    default = "hello"
+  ];
 }
 
 message TestPackedEnumSmallRange {
@@ -1765,7 +2465,10 @@ message TestPackedEnumSmallRange {
     BAR = 2;
     BAZ = 3;
   }
-  repeated NestedEnum vals = 1 [packed = true];
+
+  repeated NestedEnum vals = 1 [
+    features.repeated_field_encoding = PACKED
+  ];
 }
 
 message EnumsForBenchmark {
@@ -1787,6 +2490,7 @@ message EnumsForBenchmark {
     A14 = 14;
     A15 = 15;
   }
+
   // Has a few holes, bitmap can be used.
   enum AlmostFlat {
     B0 = 0;
@@ -1806,6 +2510,7 @@ message EnumsForBenchmark {
     B17 = 17;
     B19 = 19;
   }
+
   enum Sparse {
     C536 = 536;
     C8387 = 8387;
@@ -1862,25 +2567,39 @@ message TestMessageWithManyRepeatedPtrFields {
 }
 
 message MessageCreatorZeroInit {
-  optional int32 i = 1;
-  optional double d = 2;
-  optional MessageCreatorZeroInit m = 3;
+  int32 i = 1;
+  double d = 2;
+  MessageCreatorZeroInit m = 3;
+
   oneof one {
     string os = 10;
-    string oc = 11 [ctype=CORD];
+    string oc = 11 [
+      ctype = CORD
+    ];
+
     fixed64 of = 12;
-    MessageCreatorZeroInit ol = 13 [lazy=true];
+    MessageCreatorZeroInit ol = 13 [
+      lazy = true
+    ];
   }
 }
 
 message MessageCreatorMemcpy {
-  optional string s = 1;
-  repeated int32 i = 2 [packed=true];
-  optional MessageCreatorMemcpy m = 3 [lazy=true];
+  string s = 1;
+  repeated int32 i = 2 [
+    features.repeated_field_encoding = PACKED
+  ];
+
+  MessageCreatorMemcpy m = 3 [
+    lazy = true
+  ];
+
   map<int32, int32> m2 = 4;
 }
 
 message MessageCreatorFunc {
   // This one is ArenaDtorNeeds::kRequired so we must run the constructor.
-  optional string c = 3 [ctype=CORD];
+  string c = 3 [
+    ctype = CORD
+  ];
 }
diff --git a/Protos/upstream/google/protobuf/unittest_lite.proto b/Protos/upstream/google/protobuf/unittest_lite.proto
index 4bc78c4de..0a6c0456c 100644
--- a/Protos/upstream/google/protobuf/unittest_lite.proto
+++ b/Protos/upstream/google/protobuf/unittest_lite.proto
@@ -72,6 +72,7 @@ message TestAllTypesLite {
   string optional_string_piece = 24 [ctype = STRING_PIECE];
 
   string optional_cord = 25 [ctype = CORD];
+  bytes optional_bytes_cord = 86 [ctype = CORD];
 
   // Defined in unittest_import_public.proto
   protobuf_unittest_import.PublicImportMessageLite
@@ -261,6 +262,7 @@ extend TestAllExtensionsLite {
   // TODO: ctype=CORD is not supported for extension. Add
   // ctype=CORD option back after it is supported.
   string optional_cord_extension_lite = 25;
+  bytes optional_bytes_cord_extension_lite = 86;
   protobuf_unittest_import.PublicImportMessageLite
       optional_public_import_message_extension_lite = 26;
   TestAllTypesLite.NestedMessage optional_lazy_message_extension_lite = 27
diff --git a/Protos/upstream/google/protobuf/unittest_no_field_presence.proto b/Protos/upstream/google/protobuf/unittest_no_field_presence.proto
index cc02acc91..cb25084c6 100644
--- a/Protos/upstream/google/protobuf/unittest_no_field_presence.proto
+++ b/Protos/upstream/google/protobuf/unittest_no_field_presence.proto
@@ -102,6 +102,13 @@ message TestAllTypes {
   }
 }
 
+message TestAllMapTypes {
+  map<int32, bytes> map_int32_bytes = 1;
+  map<int32, ForeignEnum> map_int32_foreign_enum = 2;
+  map<int32, ForeignMessage> map_int32_foreign_message = 3;
+  map<int32, ExplicitForeignMessage> map_int32_explicit_foreign_message = 4;
+}
+
 message TestProto2Required {
   protobuf_unittest.TestRequired proto2 = 1;
 }
diff --git a/Protos/upstream/google/protobuf/unittest_proto3_arena.proto b/Protos/upstream/google/protobuf/unittest_proto3_arena.proto
index 96a9ea85e..ea801cef6 100644
--- a/Protos/upstream/google/protobuf/unittest_proto3_arena.proto
+++ b/Protos/upstream/google/protobuf/unittest_proto3_arena.proto
@@ -67,6 +67,7 @@ message TestAllTypes {
 
   string optional_string_piece = 24 [ctype=STRING_PIECE];
   string optional_cord = 25 [ctype=CORD];
+  bytes optional_bytes_cord = 86 [ctype=CORD];
 
   // Defined in unittest_import_public.proto
   protobuf_unittest_import.PublicImportMessage