Refactor: split BuildAssetUriResolver into AnalysisDriverModel and AnalysisDriverModelUriResolver.

`AnalysisDriverModel` is `build_runner`'s state related to build steps that use analysis, including an in-memory filesystem for use by the analyzer.

`UriResolver` is the analyzer's view of that state.

Author: davidmorgan

build_resolvers/CHANGELOG.md

@@ -1,5 +1,8 @@
 ## 2.4.4-wip
 
+- Refactor `BuildAssetUriResolver` into `AnalysisDriverModel` and
+  `AnalysisDriverModelUriResolver`.
+
 ## 2.4.3
 
 - Require the latest analyzer, and stop passing the `withNullability`

build_resolvers/lib/src/analysis_driver.dart

@@ -12,13 +12,15 @@ import 'package:package_config/package_config.dart' show PackageConfig;
 import 'package:path/path.dart' as p;
 import 'package:pub_semver/pub_semver.dart';
 
+import 'analysis_driver_model.dart';
+import 'analysis_driver_model_uri_resolver.dart';
 import 'build_asset_uri_resolver.dart';
 
 /// Builds an [AnalysisDriverForPackageBuild] backed by a summary SDK.
 ///
-/// Any code must be resolvable through [buildAssetUriResolver].
+/// Any code must be resolvable through [analysisDriverModel].
 Future<AnalysisDriverForPackageBuild> analysisDriver(
-  BuildAssetUriResolver buildAssetUriResolver,
+  AnalysisDriverModel analysisDriverModel,
   AnalysisOptions analysisOptions,
   String sdkSummaryPath,
   PackageConfig packageConfig,
@@ -27,12 +29,12 @@ Future<AnalysisDriverForPackageBuild> analysisDriver(
     analysisOptions: analysisOptions,
     packages: _buildAnalyzerPackages(
       packageConfig,
-      buildAssetUriResolver.resourceProvider,
+      analysisDriverModel.resourceProvider,
     ),
-    resourceProvider: buildAssetUriResolver.resourceProvider,
+    resourceProvider: analysisDriverModel.resourceProvider,
     sdkSummaryBytes: File(sdkSummaryPath).readAsBytesSync(),
     uriResolvers: [
-      buildAssetUriResolver,
+      AnalysisDriverModelUriResolver(analysisDriverModel),
     ],
   );
 }

build_resolvers/lib/src/analysis_driver_model.dart

@@ -0,0 +1,54 @@
+// 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:async';
+
+import 'package:analyzer/file_system/memory_file_system.dart';
+// ignore: implementation_imports
+import 'package:analyzer/src/clients/build_resolvers/build_resolvers.dart';
+import 'package:build/build.dart';
+
+/// Manages analysis driver and related build state.
+///
+/// - Tracks the import graph of all sources needed for analysis.
+/// - Given a set of entrypoints, adds them to known sources, optionally with
+///   their transitive imports.
+/// - Given a set of entrypoints, informs a `BuildStep` which inputs it now
+///   depends on because of analysis.
+/// - Maintains an in-memory filesystem that is the analyzer's view of the
+///   build.
+/// - Notifies the analyzer of changes to that in-memory filesystem.
+abstract class AnalysisDriverModel {
+  /// In-memory filesystem for the analyzer.
+  abstract final MemoryResourceProvider resourceProvider;
+
+  /// Notifies that [step] has completed.
+  ///
+  /// All build steps must complete before [reset] is called.
+  void notifyComplete(BuildStep step);
+
+  /// Clear cached information specific to an individual build.
+  void reset();
+
+  /// Attempts to parse [uri] into an [AssetId] and returns it if it is cached.
+  ///
+  /// Handles 'package:' or 'asset:' URIs, as well as 'file:' URIs of the form
+  /// `/$packageName/$assetPath`.
+  ///
+  /// Returns null if the Uri cannot be parsed or is not cached.
+  AssetId? lookupCachedAsset(Uri uri);
+
+  /// Updates [resourceProvider] and the analysis driver given by
+  /// `withDriverResource`  with updated versions of [entryPoints].
+  ///
+  /// If [transitive], then all the transitive imports from [entryPoints] are
+  /// also updated.
+  Future<void> performResolve(
+      BuildStep buildStep,
+      List<AssetId> entryPoints,
+      Future<void> Function(
+              FutureOr<void> Function(AnalysisDriverForPackageBuild))
+          withDriverResource,
+      {required bool transitive});
+}

build_resolvers/lib/src/analysis_driver_model_uri_resolver.dart

@@ -0,0 +1,66 @@
+// 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 'package:analyzer/source/file_source.dart';
+// ignore: implementation_imports
+import 'package:analyzer/src/clients/build_resolvers/build_resolvers.dart';
+import 'package:build/build.dart';
+import 'package:path/path.dart' as p;
+
+import 'analysis_driver_model.dart';
+
+const _ignoredSchemes = ['dart', 'dart-ext'];
+
+/// A [UriResolver] on top of [AnalysisDriverModel]'s in-memory filesystem.
+class AnalysisDriverModelUriResolver implements UriResolver {
+  final AnalysisDriverModel analysisDriverModel;
+  AnalysisDriverModelUriResolver(this.analysisDriverModel);
+
+  @override
+  Source? resolveAbsolute(Uri uri, [Uri? actualUri]) {
+    final assetId = parseAsset(uri);
+    if (assetId == null) return null;
+
+    var file = analysisDriverModel.resourceProvider.getFile(assetPath(assetId));
+    return FileSource(file, assetId.uri);
+  }
+
+  @override
+  Uri pathToUri(String path) {
+    var pathSegments = p.posix.split(path);
+    var packageName = pathSegments[1];
+    if (pathSegments[2] == 'lib') {
+      return Uri(
+        scheme: 'package',
+        pathSegments: [packageName].followedBy(pathSegments.skip(3)),
+      );
+    } else {
+      return Uri(
+        scheme: 'asset',
+        pathSegments: [packageName].followedBy(pathSegments.skip(2)),
+      );
+    }
+  }
+
+  /// Attempts to parse [uri] into an [AssetId].
+  ///
+  /// Handles 'package:' or 'asset:' URIs, as well as 'file:' URIs that have the
+  /// same pattern used by [assetPath].
+  ///
+  /// Returns null if the Uri cannot be parsed.
+  static AssetId? parseAsset(Uri uri) {
+    if (_ignoredSchemes.any(uri.isScheme)) return null;
+    if (uri.isScheme('package') || uri.isScheme('asset')) {
+      return AssetId.resolve(uri);
+    }
+    if (uri.isScheme('file')) {
+      final parts = p.split(uri.path);
+      return AssetId(parts[1], p.posix.joinAll(parts.skip(2)));
+    }
+    return null;
+  }
+
+  static String assetPath(AssetId assetId) =>
+      p.posix.join('/${assetId.package}', assetId.path);
+}

build_resolvers/lib/src/build_asset_uri_resolver.dart

@@ -9,7 +9,6 @@ import 'dart:isolate';
 import 'package:analyzer/dart/analysis/utilities.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
-import 'package:analyzer/source/file_source.dart';
 // ignore: implementation_imports
 import 'package:analyzer/src/clients/build_resolvers/build_resolvers.dart';
 import 'package:build/build.dart' show AssetId, BuildStep;
@@ -19,11 +18,13 @@ import 'package:graphs/graphs.dart';
 import 'package:path/path.dart' as p;
 import 'package:stream_transform/stream_transform.dart';
 
+import 'analysis_driver_model.dart';
+
 const _ignoredSchemes = ['dart', 'dart-ext'];
 
 const transitiveDigestExtension = '.transitive_digest';
 
-class BuildAssetUriResolver extends UriResolver {
+class BuildAssetUriResolver implements AnalysisDriverModel {
   /// A cache of the directives for each Dart library.
   ///
   /// This is stored across builds and is only invalidated if we read a file and
@@ -41,6 +42,7 @@ class BuildAssetUriResolver extends UriResolver {
   /// updated in the analysis driver.
   final _needsChangeFile = HashSet<String>();
 
+  @override
   final resourceProvider = MemoryResourceProvider(context: p.posix);
 
   /// The assets which are known to be readable at some point during the current
@@ -66,11 +68,7 @@ class BuildAssetUriResolver extends UriResolver {
   /// This is not used within testing contexts or similar custom contexts.
   static final BuildAssetUriResolver sharedInstance = BuildAssetUriResolver();
 
-  /// Updates [resourceProvider] and the analysis driver given by
-  /// `withDriverResource`  with updated versions of [entryPoints].
-  ///
-  /// If [transitive], then all the transitive imports from [entryPoints] are
-  /// also updated.
+  @override
   Future<void> performResolve(
       BuildStep buildStep,
       List<AssetId> entryPoints,
@@ -186,12 +184,7 @@ class BuildAssetUriResolver extends UriResolver {
     return null;
   }
 
-  /// Attempts to parse [uri] into an [AssetId] and returns it if it is cached.
-  ///
-  /// Handles 'package:' or 'asset:' URIs, as well as 'file:' URIs that have the
-  /// same pattern used by [assetPath].
-  ///
-  /// Returns null if the Uri cannot be parsed or is not cached.
+  @override
   AssetId? lookupCachedAsset(Uri uri) {
     final assetId = parseAsset(uri);
     if (assetId == null || !_cachedAssetDigests.containsKey(assetId)) {
@@ -201,43 +194,18 @@ class BuildAssetUriResolver extends UriResolver {
     return assetId;
   }
 
+  @override
   void notifyComplete(BuildStep step) {
     _buildStepTransitivelyResolvedAssets.remove(step);
   }
 
-  /// Clear cached information specific to an individual build.
+  @override
   void reset() {
     assert(_buildStepTransitivelyResolvedAssets.isEmpty,
         'Reset was called before all build steps completed');
     globallySeenAssets.clear();
     _needsChangeFile.clear();
   }
-
-  @override
-  Source? resolveAbsolute(Uri uri, [Uri? actualUri]) {
-    final assetId = parseAsset(uri);
-    if (assetId == null) return null;
-
-    var file = resourceProvider.getFile(assetPath(assetId));
-    return FileSource(file, assetId.uri);
-  }
-
-  @override
-  Uri pathToUri(String path) {
-    var pathSegments = p.posix.split(path);
-    var packageName = pathSegments[1];
-    if (pathSegments[2] == 'lib') {
-      return Uri(
-        scheme: 'package',
-        pathSegments: [packageName].followedBy(pathSegments.skip(3)),
-      );
-    } else {
-      return Uri(
-        scheme: 'asset',
-        pathSegments: [packageName].followedBy(pathSegments.skip(2)),
-      );
-    }
-  }
 }
 
 String assetPath(AssetId assetId) =>