Split post process builder state out of the main graph.

build_runner/test/generate/watch_test.dart

@@ -426,6 +426,10 @@ void main() {
           cachedGraph,
           equalsAssetGraph(expectedGraph, checkPreviousInputsDigest: false),
         );
+        expect(
+          cachedGraph.allPostProcessBuildStepOutputs,
+          expectedGraph.allPostProcessBuildStepOutputs,
+        );
       });
 
       test('ignores events from nested packages', () async {

build_runner/test/server/asset_handler_test.dart

@@ -10,6 +10,7 @@ import 'package:build_runner/src/server/server.dart';
 import 'package:build_runner_core/build_runner_core.dart';
 import 'package:build_runner_core/src/asset_graph/graph.dart';
 import 'package:build_runner_core/src/asset_graph/node.dart';
+import 'package:build_runner_core/src/asset_graph/post_process_build_step_id.dart';
 import 'package:build_runner_core/src/generate/build_phases.dart';
 import 'package:build_runner_core/src/generate/options.dart';
 import 'package:build_runner_core/src/package_graph/target_graph.dart';
@@ -48,9 +49,11 @@ void main() {
   void addAsset(String id, String content, {bool deleted = false}) {
     var node = makeAssetNode(id, [], computeDigest(AssetId.parse(id), 'a'));
     if (deleted) {
-      node = node.rebuild(
-        (b) => b..deletedBy.add(node.id.addExtension('.post_anchor.1')),
-      );
+      node = node.rebuild((b) {
+        b.deletedBy.add(
+          PostProcessBuildStepId(input: node.id, actionNumber: 1),
+        );
+      });
     }
     graph.add(node);
     delegate.testing.writeString(node.id, content);

build_runner/test/server/serve_handler_test.dart

@@ -15,6 +15,7 @@ import 'package:build_runner/src/server/server.dart';
 import 'package:build_runner_core/build_runner_core.dart';
 import 'package:build_runner_core/src/asset_graph/graph.dart';
 import 'package:build_runner_core/src/asset_graph/node.dart';
+import 'package:build_runner_core/src/asset_graph/post_process_build_step_id.dart';
 import 'package:build_runner_core/src/generate/build_phases.dart';
 import 'package:build_runner_core/src/generate/options.dart';
 import 'package:build_runner_core/src/generate/performance_tracker.dart';
@@ -139,9 +140,11 @@ void main() {
   void addSource(String id, String content, {bool deleted = false}) {
     var node = makeAssetNode(id, [], computeDigest(AssetId.parse(id), content));
     if (deleted) {
-      node = node.rebuild(
-        (b) => b..deletedBy.add(node.id.addExtension('.post_anchor.1')),
-      );
+      node = node.rebuild((b) {
+        b.deletedBy.add(
+          PostProcessBuildStepId(input: node.id, actionNumber: 1),
+        );
+      });
     }
     assetGraph.add(node);
     readerWriter.testing.writeString(node.id, content);

build_runner_core/CHANGELOG.md

@@ -27,6 +27,8 @@
 - Add `reportUnusedAssetsForInput` to `BuildOptions`, to listen for when
   a builder notifies that an asset is unused.
 - Use `LibraryCycleGraphLoader` to load transitive deps for analysis.
+- Track post process builder outputs separately from the main graph Instead of
+  in `postProcessAnchor` nodes.
 
 ## 8.0.0
 

build_runner_core/lib/src/asset_graph/graph.dart

@@ -14,6 +14,7 @@ import 'package:build/src/internal.dart';
 import 'package:built_collection/built_collection.dart';
 import 'package:crypto/crypto.dart';
 import 'package:glob/glob.dart';
+import 'package:meta/meta.dart';
 import 'package:package_config/package_config.dart';
 import 'package:watcher/watcher.dart';
 
@@ -23,6 +24,8 @@ import '../generate/phase.dart';
 import '../util/constants.dart';
 import 'exceptions.dart';
 import 'node.dart';
+import 'post_process_build_step_id.dart';
+import 'serializers.dart';
 
 part 'serialization.dart';
 
@@ -46,6 +49,14 @@ class AssetGraph implements GeneratedAssetHider {
 
   final BuiltMap<String, LanguageVersion?> packageLanguageVersions;
 
+  /// All post process build steps outputs, indexed by package then
+  /// [PostProcessBuildStepId].
+  ///
+  /// Created with empty outputs at the start of the build if it's a new build
+  /// step; or deserialized with previous build outputs if it has run before.
+  final Map<String, Map<PostProcessBuildStepId, Set<AssetId>>>
+  _postProcessBuildStepOutputs = {};
+
   AssetGraph._(
     this.buildPhasesDigest,
     this.dartVersion,
@@ -93,6 +104,10 @@ class AssetGraph implements GeneratedAssetHider {
 
   List<int> serialize() => _AssetGraphSerializer(this).serialize();
 
+  @visibleForTesting
+  Map<String, Map<PostProcessBuildStepId, Set<AssetId>>>
+  get allPostProcessBuildStepOutputs => _postProcessBuildStepOutputs;
+
   /// Checks if [id] exists in the graph.
   bool contains(AssetId id) =>
       _nodesByPackage[id.package]?.containsKey(id.path) ?? false;
@@ -243,9 +258,6 @@ class AssetGraph implements GeneratedAssetHider {
     var node = get(id);
     if (node == null) return removedIds;
     removedIds.add(id);
-    for (var anchor in node.anchorOutputs.toList()) {
-      _removeRecursive(anchor, removedIds: removedIds);
-    }
     for (var output in node.primaryOutputs.toList()) {
       _removeRecursive(output, removedIds: removedIds);
     }
@@ -290,6 +302,12 @@ class AssetGraph implements GeneratedAssetHider {
     if (node.type != NodeType.missingSource) {
       _nodesByPackage[id.package]!.remove(id.path);
     }
+
+    // Remove post build action applications with removed assets as inputs.
+    for (final packageOutputs in _postProcessBuildStepOutputs.values) {
+      packageOutputs.removeWhere((id, _) => removedIds!.contains(id.input));
+    }
+
     return removedIds;
   }
 
@@ -301,6 +319,31 @@ class AssetGraph implements GeneratedAssetHider {
   Iterable<AssetNode> packageNodes(String package) =>
       _nodesByPackage[package]?.values ?? [];
 
+  /// All the post process build steps for `package`.
+  Iterable<PostProcessBuildStepId> postProcessBuildStepIds({
+    required String package,
+  }) => _postProcessBuildStepOutputs[package]?.keys ?? const [];
+
+  /// Creates or updates state for a [PostProcessBuildStepId].
+  void updatePostProcessBuildStep(
+    PostProcessBuildStepId buildStepId, {
+    required Set<AssetId> outputs,
+  }) {
+    _postProcessBuildStepOutputs.putIfAbsent(
+          buildStepId.input.package,
+          () => {},
+        )[buildStepId] =
+        outputs;
+  }
+
+  /// Gets outputs of a [PostProcessBuildStepId].
+  ///
+  /// These are set using [updatePostProcessBuildStep] during the build, then
+  /// used to clean up prior outputs in the next build.
+  Iterable<AssetId> postProcessBuildStepOutputs(PostProcessBuildStepId action) {
+    return _postProcessBuildStepOutputs[action.input.package]![action]!;
+  }
+
   /// All the generated outputs in the graph.
   Iterable<AssetId> get outputs =>
       allNodes.where((n) => n.type == NodeType.generated).map((n) => n.id);
@@ -547,7 +590,7 @@ class AssetGraph implements GeneratedAssetHider {
           ),
         );
       } else if (phase is PostBuildPhase) {
-        _addPostBuildPhaseAnchors(phase, allInputs);
+        _addPostBuildActionApplications(phase, allInputs);
       } else {
         throw StateError('Unrecognized phase type $phase');
       }
@@ -600,27 +643,21 @@ class AssetGraph implements GeneratedAssetHider {
     return phaseOutputs;
   }
 
-  /// Adds all [AssetNode.postProcessAnchor]s for [phase] given [allInputs];
-  ///
-  /// Does not return anything because [AssetNode.postProcessAnchor]s are
-  /// synthetic and should not be treated as inputs.
-  void _addPostBuildPhaseAnchors(PostBuildPhase phase, Set<AssetId> allInputs) {
-    var actionNum = 0;
+  /// Adds all [PostProcessBuildStepId]s for [phase] given [allInputs];
+  void _addPostBuildActionApplications(
+    PostBuildPhase phase,
+    Set<AssetId> allInputs,
+  ) {
+    var actionNumber = 0;
     for (var action in phase.builderActions) {
       var inputs = allInputs.where((input) => _actionMatches(action, input));
       for (var input in inputs) {
-        var buildOptionsNodeId = builderOptionsIdForAction(action, actionNum);
-        var anchor = AssetNode.postProcessAnchorForInputAndAction(
-          input,
-          actionNum,
-          buildOptionsNodeId,
+        updatePostProcessBuildStep(
+          PostProcessBuildStepId(input: input, actionNumber: actionNumber),
+          outputs: {},
         );
-        add(anchor);
-        updateNode(input, (nodeBuilder) {
-          nodeBuilder.anchorOutputs.add(anchor.id);
-        });
       }
-      actionNum++;
+      actionNumber++;
     }
   }
 
@@ -762,11 +799,14 @@ class AssetGraph implements GeneratedAssetHider {
 Digest computeBuilderOptionsDigest(BuilderOptions options) =>
     md5.convert(utf8.encode(json.encode(options.config)));
 
-AssetId builderOptionsIdForAction(BuildAction action, int actionNum) {
+AssetId builderOptionsIdForAction(BuildAction action, int actionNumber) {
   if (action is InBuildPhase) {
-    return AssetId(action.package, 'Phase$actionNum.builderOptions');
+    return AssetId(action.package, 'Phase$actionNumber.builderOptions');
   } else if (action is PostBuildAction) {
-    return AssetId(action.package, 'PostPhase$actionNum.builderOptions');
+    return PostProcessBuildStepId.builderOptionsIdFor(
+      package: action.package,
+      actionNumber: actionNumber,
+    );
   } else {
     throw StateError('Unsupported action type $action');
   }