Track resolver dependencies as library cycle graphs

_test_common/lib/test_phases.dart

@@ -19,7 +19,11 @@ Future<void> wait(int milliseconds) =>
     Future.delayed(Duration(milliseconds: milliseconds));
 
 void _printOnFailure(LogRecord record) {
-  printOnFailure('$record');
+  printOnFailure(
+    '$record'
+    '${record.error == null ? '' : '  ${record.error}'}'
+    '${record.stackTrace == null ? '' : '  ${record.stackTrace}'}',
+  );
 }
 
 /// Runs [builders] in a test environment.

build/CHANGELOG.md

@@ -15,6 +15,7 @@
 - Refactor `FileBasedAssetReader` and `FileBasedAssetWriter` to `ReaderWriter`.
 - Move `BuildStepImpl` to `build_runner_core`, use `SingleStepReader` directly.
 - Add `LibraryCycleGraphLoader` for loading transitive deps for analysis.
+- Track resolver dependencies as library cycle graphs.
 
 ## 2.4.2
 

build/lib/src/internal.dart

@@ -11,6 +11,7 @@ export 'library_cycle_graph/asset_deps_loader.dart';
 export 'library_cycle_graph/library_cycle.dart';
 export 'library_cycle_graph/library_cycle_graph.dart';
 export 'library_cycle_graph/library_cycle_graph_loader.dart';
+export 'library_cycle_graph/phased_asset_deps.dart';
 export 'library_cycle_graph/phased_reader.dart';
 export 'library_cycle_graph/phased_value.dart';
 export 'state/asset_finder.dart';

build/lib/src/library_cycle_graph/asset_deps.dart

@@ -4,6 +4,7 @@
 
 import 'package:built_collection/built_collection.dart';
 import 'package:built_value/built_value.dart';
+import 'package:built_value/serializer.dart';
 
 import '../../build.dart' hide Builder;
 
@@ -17,11 +18,15 @@ part 'asset_deps.g.dart';
 /// Missing or not-yet-generated sources can be represented by this class: they
 /// have no deps.
 abstract class AssetDeps implements Built<AssetDeps, AssetDepsBuilder> {
+  static Serializer<AssetDeps> get serializer => _$assetDepsSerializer;
+
   static final AssetDeps empty = _$AssetDeps._(deps: BuiltSet());
 
   BuiltSet<AssetId> get deps;
 
   factory AssetDeps(Iterable<AssetId> deps) =>
       _$AssetDeps._(deps: BuiltSet.of(deps));
+  factory AssetDeps.build(void Function(AssetDepsBuilder) updates) =
+      _$AssetDeps;
   AssetDeps._();
 }

build/lib/src/library_cycle_graph/asset_deps_loader.dart

@@ -7,6 +7,7 @@ import 'package:analyzer/dart/ast/ast.dart';
 
 import '../asset/id.dart';
 import 'asset_deps.dart';
+import 'phased_asset_deps.dart';
 import 'phased_reader.dart';
 import 'phased_value.dart';
 
@@ -17,6 +18,8 @@ class AssetDepsLoader {
   final PhasedReader _reader;
 
   AssetDepsLoader(this._reader);
+  factory AssetDepsLoader.fromDeps(PhasedAssetDeps deps) =>
+      _InMemoryAssetDepsLoader(deps);
 
   /// The phase that this loader is reading build state at.
   int get phase => _reader.phase;
@@ -57,3 +60,32 @@ class AssetDepsLoader {
     return result.build();
   }
 }
+
+// An [AssetDepsLoader] from already-loaded asset deps.
+class _InMemoryAssetDepsLoader implements AssetDepsLoader {
+  final Future<PhasedValue<AssetDeps>> _empty = Future.value(
+    PhasedValue.fixed(AssetDeps.empty),
+  );
+  PhasedAssetDeps phasedAssetDeps;
+
+  _InMemoryAssetDepsLoader(this.phasedAssetDeps);
+
+  // This is important: it prevents LibraryCycleGraphLoader from trying to load
+  // data that is not in an incomplete [phasedAssetDeps].
+  @override
+  int get phase => phasedAssetDeps.phase;
+
+  @override
+  ExpiringValue<AssetDeps> _parse(AssetId id, ExpiringValue<String> content) =>
+      throw UnimplementedError();
+
+  @override
+  PhasedReader get _reader => throw UnimplementedError();
+
+  @override
+  Future<PhasedValue<AssetDeps>> load(AssetId id) {
+    var result = phasedAssetDeps.assetDeps[id];
+    if (result == null) return _empty;
+    return Future.value(result);
+  }
+}

build/lib/src/library_cycle_graph/library_cycle.dart

@@ -19,4 +19,7 @@ abstract class LibraryCycle
   factory LibraryCycle([void Function(LibraryCycleBuilder) updates]) =
       _$LibraryCycle;
   LibraryCycle._();
+
+  factory LibraryCycle.of(Iterable<AssetId> ids) =>
+      _$LibraryCycle._(ids: ids.toBuiltSet());
 }

build/lib/src/library_cycle_graph/library_cycle_graph.dart

@@ -4,6 +4,7 @@
 
 import 'package:built_collection/built_collection.dart';
 import 'package:built_value/built_value.dart';
+import 'package:built_value/serializer.dart';
 
 import '../asset/id.dart';
 import 'library_cycle.dart';
@@ -13,6 +14,8 @@ part 'library_cycle_graph.g.dart';
 /// A directed acyclic graph of [LibraryCycle]s.
 abstract class LibraryCycleGraph
     implements Built<LibraryCycleGraph, LibraryCycleGraphBuilder> {
+  static Serializer<LibraryCycleGraph> get serializer =>
+      _$libraryCycleGraphSerializer;
   LibraryCycle get root;
   BuiltList<LibraryCycleGraph> get children;
 
@@ -21,7 +24,7 @@ abstract class LibraryCycleGraph
   LibraryCycleGraph._();
 
   /// All subgraphs in the graph, including the root.
-  Iterable<LibraryCycleGraph> get transitiveGraphs {
+  Iterable<LibraryCycleGraph> transitiveGraphs() {
     final result = Set<LibraryCycleGraph>.identity();
     final nextGraphs = [this];
 
@@ -40,8 +43,8 @@ abstract class LibraryCycleGraph
   // graph rather than being expanded into an explicit set of nodes. So, remove
   // uses of this. If in the end it's still needed, investigate if it needs to
   // be optimized.
-  Iterable<AssetId> get transitiveDeps sync* {
-    for (final graph in transitiveGraphs) {
+  Iterable<AssetId> transitiveDeps() sync* {
+    for (final graph in transitiveGraphs()) {
       yield* graph.root.ids;
     }
   }

build/lib/src/library_cycle_graph/library_cycle_graph_loader.dart

@@ -12,6 +12,7 @@ import 'asset_deps.dart';
 import 'asset_deps_loader.dart';
 import 'library_cycle.dart';
 import 'library_cycle_graph.dart';
+import 'phased_asset_deps.dart';
 import 'phased_value.dart';
 
 /// Loads [LibraryCycleGraph]s during a phased build.
@@ -482,9 +483,14 @@ class LibraryCycleGraphLoader {
     AssetId id,
   ) async {
     final graph = await libraryCycleGraphOf(assetDepsLoader, id);
-    return graph.valueAt(phase: assetDepsLoader.phase).transitiveDeps;
+    return graph.valueAt(phase: assetDepsLoader.phase).transitiveDeps();
   }
 
+  /// Serializable data from which the library cycle graphs can be
+  /// reconstructed.
+  PhasedAssetDeps phasedAssetDeps() =>
+      PhasedAssetDeps((b) => b.assetDeps.addAll(_assetDeps));
+
   @override
   String toString() => '''
 LibraryCycleGraphLoader(

build/lib/src/library_cycle_graph/phased_asset_deps.dart

@@ -0,0 +1,60 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:math';
+
+import 'package:built_collection/built_collection.dart';
+import 'package:built_value/built_value.dart';
+import 'package:built_value/serializer.dart';
+
+import '../asset/id.dart';
+import 'asset_deps.dart';
+import 'phased_value.dart';
+
+part 'phased_asset_deps.g.dart';
+
+/// Serializable data from which library cycle graphs can be reconstructed.
+///
+/// Pass to `AssetDepsLoader.fromDeps` then use that to create a
+/// `LibraryCycleGraphLoader`.
+abstract class PhasedAssetDeps
+    implements Built<PhasedAssetDeps, PhasedAssetDepsBuilder> {
+  static Serializer<PhasedAssetDeps> get serializer =>
+      _$phasedAssetDepsSerializer;
+
+  BuiltMap<AssetId, PhasedValue<AssetDeps>> get assetDeps;
+
+  factory PhasedAssetDeps([void Function(PhasedAssetDepsBuilder) b]) =
+      _$PhasedAssetDeps;
+  PhasedAssetDeps._();
+
+  factory PhasedAssetDeps.of(Map<AssetId, PhasedValue<AssetDeps>> assetDeps) =>
+      _$PhasedAssetDeps._(assetDeps: assetDeps.build());
+
+  /// Returns this data with [other] added to it.
+  PhasedAssetDeps addAll(PhasedAssetDeps other) {
+    final result = toBuilder();
+    for (final entry in other.assetDeps.entries) {
+      result.assetDeps[entry.key] = entry.value;
+    }
+    return result.build();
+  }
+
+  /// The max phase before there is any incomplete data, or 0xffffffff if there
+  /// is no incomplete data.
+  @memoized
+  int get phase {
+    int? result;
+    for (final entry in assetDeps.values) {
+      if (!entry.isComplete) {
+        if (result == null) {
+          result = entry.expiresAfter;
+        } else {
+          result = min(result, entry.expiresAfter!);
+        }
+      }
+    }
+    return result ?? 0xffffffff;
+  }
+}