Move input tracking out of AssetReader to SingleStepReader.

`BuildStepImpl` always uses a `SingleStepReader`.

_test_common/lib/in_memory_reader_writer.dart

@@ -24,36 +24,35 @@ class InMemoryRunnerAssetReaderWriter extends InMemoryAssetReaderWriter
   factory InMemoryRunnerAssetReaderWriter({String? rootPackage}) {
     final filesystem = InMemoryFilesystem();
     return InMemoryRunnerAssetReaderWriter.using(
+      assetsRead: {},
       rootPackage: rootPackage ?? 'unset',
       assetFinder: InMemoryAssetFinder(filesystem, rootPackage),
       assetPathProvider: const InMemoryAssetPathProvider(),
       filesystem: filesystem,
       cache: const PassthroughFilesystemCache(),
-      inputTracker: InputTracker(),
     );
   }
 
   InMemoryRunnerAssetReaderWriter.using({
+    required super.assetsRead,
     required super.rootPackage,
     required super.assetFinder,
     required super.assetPathProvider,
     required super.filesystem,
     required super.cache,
-    required super.inputTracker,
   }) : super.using();
 
   @override
   InMemoryRunnerAssetReaderWriter copyWith({
     AssetPathProvider? assetPathProvider,
     FilesystemCache? cache,
-    InputTracker? inputTracker,
   }) => InMemoryRunnerAssetReaderWriter.using(
+    assetsRead: assetsRead,
     rootPackage: rootPackage,
     assetFinder: assetFinder,
     assetPathProvider: assetPathProvider ?? this.assetPathProvider,
     filesystem: filesystem,
     cache: cache ?? this.cache,
-    inputTracker: inputTracker ?? this.inputTracker,
   );
 
   @override

build/lib/src/builder/build_step.dart

@@ -5,7 +5,6 @@ import 'dart:async';
 import 'dart:convert';
 
 import 'package:analyzer/dart/element/element.dart';
-import 'package:meta/meta.dart';
 import 'package:package_config/package_config_types.dart';
 
 import '../analyzer/resolver.dart';
@@ -19,7 +18,6 @@ import '../resource/resource.dart';
 /// This represents a single [inputId], logic around resolving as a library,
 /// and the ability to read and write assets as allowed by the underlying build
 /// system.
-@sealed
 abstract class BuildStep implements AssetReader, AssetWriter {
   /// The primary for this build step.
   AssetId get inputId;

build/lib/src/generate/run_builder.dart

@@ -3,6 +3,8 @@
 // BSD-style license that can be found in the LICENSE file.
 import 'dart:isolate';
 
+// ignore: implementation_imports
+import 'package:build_runner_core/src/generate/build_step_impl.dart';
 import 'package:logging/logging.dart';
 import 'package:package_config/package_config.dart';
 
@@ -11,7 +13,6 @@ import '../asset/id.dart';
 import '../asset/reader.dart';
 import '../asset/writer.dart';
 import '../builder/build_step.dart';
-import '../builder/build_step_impl.dart';
 import '../builder/builder.dart';
 import '../builder/logging.dart';
 import '../resource/resource.dart';

build/lib/src/internal.dart

@@ -10,5 +10,4 @@ export 'state/asset_finder.dart';
 export 'state/asset_path_provider.dart';
 export 'state/filesystem.dart';
 export 'state/filesystem_cache.dart';
-export 'state/input_tracker.dart';
 export 'state/reader_state.dart';

build/lib/src/state/reader_state.dart

@@ -7,7 +7,6 @@ import 'asset_finder.dart';
 import 'asset_path_provider.dart';
 import 'filesystem.dart';
 import 'filesystem_cache.dart';
-import 'input_tracker.dart';
 
 /// Provides access to the state backing an [AssetReader].
 extension AssetReaderStateExtension on AssetReader {
@@ -38,26 +37,11 @@ extension AssetReaderStateExtension on AssetReader {
     return (this as AssetReaderState).assetFinder;
   }
 
-  InputTracker? get inputTracker =>
-      this is AssetReaderState ? (this as AssetReaderState).inputTracker : null;
-
   AssetPathProvider get assetPathProvider {
     _requireIsAssetReaderState();
     return (this as AssetReaderState).assetPathProvider;
   }
 
-  /// Gets [inputTracker] or throws a descriptive error if it is `null`.
-  InputTracker get requireInputTracker {
-    final result = inputTracker;
-    if (result == null) {
-      _requireIsAssetReaderState();
-      throw StateError(
-        '`AssetReader` is missing required `inputTracker`: $this',
-      );
-    }
-    return result;
-  }
-
   /// Throws if `this` is not an [AssetReaderState].
   void _requireIsAssetReaderState() {
     if (this is! AssetReaderState) {
@@ -91,10 +75,6 @@ abstract interface class AssetReaderState {
   /// globbing in arbitrary packages, is hidden from generators.
   AssetFinder get assetFinder;
 
-  /// The [InputTracker] that this reader records reads to; or `null` if it does
-  /// not have one.
-  InputTracker? get inputTracker;
-
   /// The [AssetPathProvider] associated with this reader.
   AssetPathProvider get assetPathProvider;
 }

build/pubspec.yaml

@@ -10,6 +10,7 @@ environment:
 dependencies:
   analyzer: '>=6.9.0 <8.0.0'
   async: ^2.5.0
+  build_runner_core: ^8.0.1-wip
   convert: ^3.0.0
   crypto: ^3.0.0
   glob: ^2.0.0

build/test/builder/build_step_impl_test.dart

@@ -9,8 +9,8 @@ import 'dart:convert';
 
 import 'package:build/build.dart';
 import 'package:build/src/builder/build_step.dart';
-import 'package:build/src/builder/build_step_impl.dart';
 import 'package:build_resolvers/build_resolvers.dart';
+import 'package:build_runner_core/src/generate/build_step_impl.dart';
 import 'package:build_test/build_test.dart';
 import 'package:package_config/package_config.dart';
 import 'package:test/test.dart';

build_resolvers/lib/src/analysis_driver_model.dart

@@ -11,7 +11,7 @@ import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/src/clients/build_resolvers/build_resolvers.dart';
 import 'package:build/build.dart';
 // ignore: implementation_imports
-import 'package:build/src/internal.dart';
+import 'package:build_runner_core/src/generate/build_step_impl.dart';
 
 import 'analysis_driver_filesystem.dart';
 
@@ -97,7 +97,7 @@ class AnalysisDriverModel {
     await withDriverResource((driver) async {
       return _performResolve(
         driver,
-        buildStep,
+        buildStep as BuildStepImpl,
         entryPoints,
         withDriverResource,
         transitive: transitive,
@@ -107,7 +107,7 @@ class AnalysisDriverModel {
 
   Future<void> _performResolve(
     AnalysisDriverForPackageBuild driver,
-    BuildStep buildStep,
+    BuildStepImpl buildStep,
     List<AssetId> entryPoints,
     Future<void> Function(
       FutureOr<void> Function(AnalysisDriverForPackageBuild),
@@ -127,7 +127,10 @@ class AnalysisDriverModel {
     }
 
     // Notify [buildStep] of its inputs.
-    buildStep.requireInputTracker.assetsRead.addAll(inputIds);
+    buildStep.inputTracker.addAll(
+      primaryInput: buildStep.inputId,
+      inputs: inputIds,
+    );
 
     // Sync changes onto the "URI resolver", the in-memory filesystem.
     for (final id in idsToSyncOntoFilesystem) {

build_resolvers/pubspec.yaml

@@ -11,6 +11,7 @@ dependencies:
   analyzer: '>=6.9.0 <8.0.0'
   async: ^2.5.0
   build: ^2.4.3-wip
+  build_runner_core: ^8.0.1-wip
   collection: ^1.17.0
   convert: ^3.1.1
   crypto: ^3.0.0

build_resolvers/test/resolver_test.dart

@@ -144,7 +144,7 @@ void runTests(ResolversFactory resolversFactory) {
         await resolver.libraryFor(entryPoint);
       },
       assetReaderChecks: (reader) {
-        expect(reader.testing.assetsRead, {
+        expect(reader.testing.inputsTracked, {
           AssetId('a', 'web/main.dart'),
           AssetId('a', 'web/main.dart.transitive_digest'),
           AssetId('a', 'web/a.dart'),
@@ -194,7 +194,7 @@ void runTests(ResolversFactory resolversFactory) {
           await resolver.libraryFor(entryPoint);
         },
         assetReaderChecks: (reader) {
-          expect(reader.testing.assetsRead, {
+          expect(reader.testing.inputsTracked, {
             AssetId('a', 'web/main.dart'),
             AssetId('a', 'web/main.dart.transitive_digest'),
             AssetId('a', 'web/a.dart'),
@@ -212,7 +212,7 @@ void runTests(ResolversFactory resolversFactory) {
           await resolver.libraryFor(entryPoint);
         },
         assetReaderChecks: (reader) {
-          expect(reader.testing.assetsRead, {
+          expect(reader.testing.inputsTracked, {
             AssetId('a', 'web/main.dart'),
             AssetId('a', 'web/main.dart.transitive_digest'),
             AssetId('a', 'web/a.dart'),

build_runner_core/lib/src/asset/reader_writer.dart

@@ -31,8 +31,6 @@ class ReaderWriter extends AssetReader
   final AssetFinder assetFinder;
   @override
   final FilesystemCache cache;
-  @override
-  final InputTracker? inputTracker;
 
   /// A [ReaderWriter] suitable for real builds.
   ///
@@ -46,8 +44,6 @@ class ReaderWriter extends AssetReader
     assetPathProvider: packageGraph,
     filesystem: IoFilesystem(),
     cache: const PassthroughFilesystemCache(),
-    // In real builds input tracking is done per generator.
-    inputTracker: null,
   );
 
   ReaderWriter.using({
@@ -56,7 +52,6 @@ class ReaderWriter extends AssetReader
     required this.assetPathProvider,
     required this.filesystem,
     required this.cache,
-    required this.inputTracker,
   });
 
   @override
@@ -69,7 +64,6 @@ class ReaderWriter extends AssetReader
     assetPathProvider: assetPathProvider ?? this.assetPathProvider,
     filesystem: filesystem,
     cache: cache ?? this.cache,
-    inputTracker: inputTracker,
   );
 
   @override

build_runner_core/lib/src/generate/build_impl.dart

@@ -18,7 +18,6 @@ import 'package:pool/pool.dart';
 import 'package:watcher/watcher.dart';
 
 import '../asset/finalized_reader.dart';
-import '../asset/reader.dart';
 import '../asset/writer.dart';
 import '../asset_graph/graph.dart';
 import '../asset_graph/node.dart';
@@ -40,9 +39,11 @@ import 'build_directory.dart';
 import 'build_result.dart';
 import 'finalized_assets_view.dart';
 import 'heartbeat.dart';
+import 'input_tracker.dart';
 import 'options.dart';
 import 'performance_tracker.dart';
 import 'phase.dart';
+import 'single_step_reader.dart';
 
 final _logger = Logger('Build');
 
@@ -561,12 +562,14 @@ class _SingleBuild {
         var wrappedWriter = AssetWriterSpy(_writer);
 
         var wrappedReader = SingleStepReader(
+          input,
           _reader,
           _assetGraph,
           phaseNumber,
           input.package,
           _isReadableNode,
           _checkInvalidInput,
+          InputTracker(_reader.filesystem),
           _getUpdatedGlobNode,
           wrappedWriter,
         );
@@ -581,9 +584,8 @@ class _SingleBuild {
         await _cleanUpStaleOutputs(builderOutputs);
         await FailureReporter.clean(phaseNumber, input);
 
-        // We may have read some inputs in the call to `_buildShouldRun`, we
-        // want to remove those.
-        wrappedReader.inputTracker.assetsRead.clear();
+        // Clear input tracking accumulated during `_buildShouldRun`.
+        wrappedReader.inputTracker.clear();
 
         var actionDescription = _actionLoggerName(
           phase,
@@ -625,6 +627,7 @@ class _SingleBuild {
         await tracker.trackStage(
           'Finalize',
           () => _setOutputsState(
+            input,
             builderOutputs,
             wrappedReader,
             wrappedReader.inputTracker,
@@ -701,22 +704,23 @@ class _SingleBuild {
     var inputNode = _assetGraph.get(input)!;
     var wrappedWriter = AssetWriterSpy(_writer);
     var wrappedReader = SingleStepReader(
+      input,
       _reader,
       _assetGraph,
       phaseNum,
       input.package,
       _isReadableNode,
       _checkInvalidInput,
+      InputTracker(_reader.filesystem),
       null,
       wrappedWriter,
     );
 
     if (!await _postProcessBuildShouldRun(anchorNode, wrappedReader)) {
       return <AssetId>[];
     }
-    // We may have read some inputs in the call to `_buildShouldRun`, we want
-    // to remove those.
-    wrappedReader.inputTracker.assetsRead.clear();
+    // Clear input tracking accumulated during `_buildShouldRun`.
+    wrappedReader.inputTracker.clear();
 
     // Clean out the impacts of the previous run
     await FailureReporter.clean(phaseNum, input);
@@ -782,6 +786,7 @@ class _SingleBuild {
     // written.
     inputNode.primaryOutputs.addAll(assetsWritten);
     await _setOutputsState(
+      input,
       assetsWritten,
       wrappedReader,
       wrappedReader.inputTracker,
@@ -999,6 +1004,7 @@ class _SingleBuild {
   /// - Setting the `previousInputsDigest` on each output based on the inputs.
   /// - Storing the error message with the [_failureReporter].
   Future<void> _setOutputsState(
+    AssetId input,
     Iterable<AssetId> outputs,
     AssetReader reader,
     InputTracker inputTracker,
@@ -1010,8 +1016,8 @@ class _SingleBuild {
     if (outputs.isEmpty) return;
     var usedInputs =
         unusedAssets != null
-            ? inputTracker.assetsRead.difference(unusedAssets)
-            : inputTracker.assetsRead;
+            ? inputTracker.inputs.difference(unusedAssets)
+            : inputTracker.inputs;
 
     final inputsDigest = await _computeCombinedDigest(
       usedInputs,