Move input tracking out of AssetReader to SingleStepReader.

`BuildStepImpl` always uses a `SingleStepReader`.

Author: davidmorgan

_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/state/input_tracker.dart

@@ -5,8 +5,58 @@
 import 'dart:collection';
 
 import '../asset/id.dart';
+import 'filesystem.dart';
 
-/// Records inputs for one generator run.
+/// Records inputs for each generator.
 class InputTracker {
-  final assetsRead = HashSet<AssetId>();
+  /// If set, when an `InputTracker` is instantiated it is stored in
+  /// `inputTrackers`.
+  static bool captureInputTrackersForTesting = false;
+
+  /// All `InputTracker`s created when `captureInputTrackersForTesting` is set,
+  /// keyed by filesystem to split by test case.
+  ///
+  /// TODO(davidmorgan): find a nicer way to do this.
+  static Map<Filesystem, List<InputTracker>> inputTrackersForTesting =
+      Map.identity();
+
+  final _inputs = HashMap<AssetId, HashSet<AssetId>>();
+
+  /// Creates an input tracker.
+  ///
+  /// [filesystem] is used to distinguish input trackers for testing, because
+  /// each test case creates a new in-memory filesystem. It's not used
+  /// otherwise.
+  InputTracker(Filesystem filesystem) {
+    if (captureInputTrackersForTesting) {
+      inputTrackersForTesting.putIfAbsent(filesystem, () => []).add(this);
+    }
+  }
+
+  HashSet<AssetId> _getInputs(AssetId primaryInput) =>
+      _inputs.putIfAbsent(primaryInput, HashSet.new);
+
+  void add({required AssetId primaryInput, required AssetId input}) {
+    _getInputs(primaryInput).add(input);
+  }
+
+  void addAll({
+    required AssetId primaryInput,
+    required Iterable<AssetId> inputs,
+  }) {
+    _getInputs(primaryInput).addAll(inputs);
+  }
+
+  Set<AssetId> inputsOf({required AssetId primaryInput}) =>
+      _getInputs(primaryInput);
+
+  Set<AssetId> allInputs() => _inputs.values.expand((s) => s).toSet();
+
+  void clear({required AssetId primaryInput}) {
+    print('clear $this');
+    _getInputs(primaryInput).clear();
+  }
+
+  @override
+  String toString() => _inputs.toString();
 }

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'),