[wpiutil] Record/Enum struct generation fix (#7538)

ProceduralStructGenerator's genRecord and genEnum were package-private, and only extractClassStruct was made public.
However, this package private visibility rendered them unable to be used by the rest of wpilib(and advanced users).

Here, ProceduralStructGenerator is split into 2 classes: StructGenerator(which generates structs) and StructFetcher(the new namespace for extractClassStruct). In addition, genRecord and genEnum have been made public methods.

wpiutil/src/main/java/edu/wpi/first/util/struct/StructFetcher.java

@@ -0,0 +1,65 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+package edu.wpi.first.util.struct;
+
+import java.util.Optional;
+
+/**
+ * A utility class for fetching the assigned struct of existing classes. These are usually public,
+ * static, and final properties with the Struct type.
+ */
+public final class StructFetcher {
+  private StructFetcher() {
+    throw new UnsupportedOperationException("This is a utility class!");
+  }
+
+  /**
+   * Returns a {@link Struct} for the given {@link StructSerializable} marked class. Due to the
+   * non-contractual nature of the marker this can fail. If the {@code struct} field could not be
+   * accessed for any reason, an empty {@link Optional} is returned.
+   *
+   * @param <T> The type of the class.
+   * @param clazz The class object to extract the struct from.
+   * @return An optional containing the struct if it could be extracted.
+   */
+  @SuppressWarnings("unchecked")
+  public static <T extends StructSerializable> Optional<Struct<T>> fetchStruct(
+      Class<? extends T> clazz) {
+    try {
+      var possibleField = Optional.ofNullable(clazz.getDeclaredField("struct"));
+      return possibleField.flatMap(
+          field -> {
+            if (Struct.class.isAssignableFrom(field.getType())) {
+              try {
+                return Optional.ofNullable((Struct<T>) field.get(null));
+              } catch (IllegalAccessException e) {
+                return Optional.empty();
+              }
+            } else {
+              return Optional.empty();
+            }
+          });
+    } catch (NoSuchFieldException e) {
+      return Optional.empty();
+    }
+  }
+
+  /**
+   * Returns a {@link Struct} for the given class. This does not do compile time checking that the
+   * class is a {@link StructSerializable}. Whenever possible it is reccomended to use {@link
+   * #fetchStruct(Class)}.
+   *
+   * @param clazz The class object to extract the struct from.
+   * @return An optional containing the struct if it could be extracted.
+   */
+  @SuppressWarnings("unchecked")
+  public static Optional<Struct<?>> fetchStructDynamic(Class<?> clazz) {
+    if (StructSerializable.class.isAssignableFrom(clazz)) {
+      return fetchStruct((Class<? extends StructSerializable>) clazz).map(struct -> struct);
+    } else {
+      return Optional.empty();
+    }
+  }
+}

wpiutil/src/main/java/edu/wpi/first/util/struct/ProceduralStructGenerator.java → wpiutil/src/main/java/edu/wpi/first/util/struct/StructGenerator.java

@@ -12,11 +12,10 @@
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
-import java.util.Optional;
 
 /** A utility class for procedurally generating {@link Struct}s from records and enums. */
-public final class ProceduralStructGenerator {
-  private ProceduralStructGenerator() {
+public final class StructGenerator {
+  private StructGenerator() {
     throw new UnsupportedOperationException("This is a utility class!");
   }
 
@@ -123,54 +122,6 @@ public static <T> void addCustomStruct(Class<T> clazz, Struct<T> struct, boolean
     }
   }
 
-  /**
-   * Returns a {@link Struct} for the given {@link StructSerializable} marked class. Due to the
-   * non-contractual nature of the marker this can fail. If the {@code struct} field could not be
-   * accessed for any reason, an empty {@link Optional} is returned.
-   *
-   * @param <T> The type of the class.
-   * @param clazz The class object to extract the struct from.
-   * @return An optional containing the struct if it could be extracted.
-   */
-  @SuppressWarnings("unchecked")
-  public static <T extends StructSerializable> Optional<Struct<T>> extractClassStruct(
-      Class<? extends T> clazz) {
-    try {
-      var possibleField = Optional.ofNullable(clazz.getDeclaredField("struct"));
-      return possibleField.flatMap(
-          field -> {
-            if (Struct.class.isAssignableFrom(field.getType())) {
-              try {
-                return Optional.ofNullable((Struct<T>) field.get(null));
-              } catch (IllegalAccessException e) {
-                return Optional.empty();
-              }
-            } else {
-              return Optional.empty();
-            }
-          });
-    } catch (NoSuchFieldException e) {
-      return Optional.empty();
-    }
-  }
-
-  /**
-   * Returns a {@link Struct} for the given class. This does not do compile time checking that the
-   * class is a {@link StructSerializable}. Whenever possible it is reccomended to use {@link
-   * #extractClassStruct(Class)}.
-   *
-   * @param clazz The class object to extract the struct from.
-   * @return An optional containing the struct if it could be extracted.
-   */
-  @SuppressWarnings("unchecked")
-  public static Optional<Struct<?>> extractClassStructDynamic(Class<?> clazz) {
-    if (StructSerializable.class.isAssignableFrom(clazz)) {
-      return extractClassStruct((Class<? extends StructSerializable>) clazz).map(struct -> struct);
-    } else {
-      return Optional.empty();
-    }
-  }
-
   /** A utility for building schema syntax in a procedural manner. */
   @SuppressWarnings("PMD.AvoidStringBufferField")
   public static class SchemaBuilder {
@@ -303,7 +254,7 @@ public boolean isImmutable() {
    * @return The generated struct.
    */
   @SuppressWarnings({"unchecked", "PMD.AvoidAccessibilityAlteration"})
-  static <R extends Record> Struct<R> genRecord(final Class<R> recordClass) {
+  public static <R extends Record> Struct<R> genRecord(final Class<R> recordClass) {
     final RecordComponent[] components = recordClass.getRecordComponents();
     final SchemaBuilder schemaBuilder = new SchemaBuilder();
     final ArrayList<Struct<?>> nestedStructs = new ArrayList<>();
@@ -329,7 +280,7 @@ static <R extends Record> Struct<R> genRecord(final Class<R> recordClass) {
         if (customStructTypeMap.containsKey(type)) {
           struct = customStructTypeMap.get(type);
         } else if (StructSerializable.class.isAssignableFrom(type)) {
-          var optStruct = extractClassStructDynamic(type);
+          var optStruct = StructFetcher.fetchStructDynamic(type);
           if (optStruct.isPresent()) {
             struct = optStruct.get();
           } else {
@@ -465,7 +416,7 @@ public boolean isImmutable() {
    * @return The generated struct.
    */
   @SuppressWarnings({"unchecked", "PMD.AvoidAccessibilityAlteration"})
-  static <E extends Enum<E>> Struct<E> genEnum(Class<E> enumClass) {
+  public static <E extends Enum<E>> Struct<E> genEnum(Class<E> enumClass) {
     final E[] enumVariants = enumClass.getEnumConstants();
     final Field[] allEnumFields = enumClass.getDeclaredFields();
     final SchemaBuilder schemaBuilder = new SchemaBuilder();
@@ -516,7 +467,7 @@ static <E extends Enum<E>> Struct<E> genEnum(Class<E> enumClass) {
         if (customStructTypeMap.containsKey(type)) {
           struct = customStructTypeMap.get(type);
         } else if (StructSerializable.class.isAssignableFrom(type)) {
-          var optStruct = extractClassStructDynamic(type);
+          var optStruct = StructFetcher.fetchStructDynamic(type);
           if (optStruct.isPresent()) {
             struct = optStruct.get();
           } else {

wpiutil/src/test/java/edu/wpi/first/util/struct/ProceduralStructGeneratorTest.java → wpiutil/src/test/java/edu/wpi/first/util/struct/StructGeneratorTest.java

@@ -4,15 +4,15 @@
 
 package edu.wpi.first.util.struct;
 
-import static edu.wpi.first.util.struct.ProceduralStructGenerator.genEnum;
-import static edu.wpi.first.util.struct.ProceduralStructGenerator.genRecord;
+import static edu.wpi.first.util.struct.StructGenerator.genEnum;
+import static edu.wpi.first.util.struct.StructGenerator.genRecord;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import org.junit.jupiter.api.Test;
 
-class ProceduralStructGeneratorTest {
+class StructGeneratorTest {
   public record CustomRecord(int int32, boolean bool, double float64, char character, short int16)
       implements StructSerializable {
     public static CustomRecord create() {
@@ -95,8 +95,7 @@ public final int hashCode() {
 
   @SuppressWarnings("unchecked")
   private <S extends StructSerializable> void testStructRoundTrip(S value) {
-    Struct<S> struct =
-        ProceduralStructGenerator.extractClassStruct((Class<S>) value.getClass()).get();
+    Struct<S> struct = StructFetcher.fetchStruct((Class<S>) value.getClass()).get();
     ByteBuffer buffer = ByteBuffer.allocate(struct.getSize());
     buffer.order(ByteOrder.LITTLE_ENDIAN);
     struct.pack(buffer, value);
@@ -108,8 +107,7 @@ private <S extends StructSerializable> void testStructRoundTrip(S value) {
 
   @SuppressWarnings("unchecked")
   private <S extends StructSerializable> void testStructDoublePack(S value) {
-    Struct<S> struct =
-        ProceduralStructGenerator.extractClassStruct((Class<S>) value.getClass()).get();
+    Struct<S> struct = StructFetcher.fetchStruct((Class<S>) value.getClass()).get();
     ByteBuffer buffer = ByteBuffer.allocate(struct.getSize());
     buffer.order(ByteOrder.LITTLE_ENDIAN);
     struct.pack(buffer, value);
@@ -123,8 +121,7 @@ private <S extends StructSerializable> void testStructDoublePack(S value) {
 
   @SuppressWarnings("unchecked")
   private <S extends StructSerializable> void testStructDoubleUnpack(S value) {
-    Struct<S> struct =
-        ProceduralStructGenerator.extractClassStruct((Class<S>) value.getClass()).get();
+    Struct<S> struct = StructFetcher.fetchStruct((Class<S>) value.getClass()).get();
     ByteBuffer buffer = ByteBuffer.allocate(struct.getSize());
     buffer.order(ByteOrder.LITTLE_ENDIAN);
     struct.pack(buffer, value);