Simplify FinalizedReader. (#3867)

* Simplify `FinalizedReader`.

* Update CHANGELOG.md.

* Update CHANGELOG.md.

Author: davidmorgan

build_runner/CHANGELOG.md

@@ -3,6 +3,7 @@
 - Use `build_test` 3.0.0.
 - Start using `package:build/src/internal.dart'.
 - Refactor `MultiPackageAssetReader` to internal `AssetFinder`.
+- `FinalizedReader` no longer implements `AssetReader`.
 
 ## 2.4.15
 

build_runner/lib/src/server/asset_graph_handler.dart

@@ -7,6 +7,7 @@ import 'dart:convert';
 import 'dart:io';
 
 import 'package:build/build.dart';
+import 'package:build_runner_core/build_runner_core.dart';
 // ignore: implementation_imports
 import 'package:build_runner_core/src/asset_graph/graph.dart';
 // ignore: implementation_imports
@@ -18,7 +19,7 @@ import 'path_to_asset_id.dart';
 
 /// A handler for `/$graph` requests under a specific `rootDir`.
 class AssetGraphHandler {
-  final AssetReader _reader;
+  final FinalizedReader _reader;
   final String _rootPackage;
   final AssetGraph _assetGraph;
 

build_runner_core/CHANGELOG.md

@@ -5,6 +5,7 @@
 - Use `build_test` 3.0.0.
 - Refactor `PathProvidingAssetReader` to `AssetPathProvider`.
 - Refactor `MultiPackageAssetReader` to internal `AssetFinder`.
+- `FinalizedReader` no longer implements `AssetReader`.
 
 ## 8.0.0
 

build_runner_core/lib/src/asset/finalized_reader.dart

@@ -18,9 +18,11 @@ import '../asset_graph/optional_output_tracker.dart';
 import '../generate/phase.dart';
 import '../package_graph/target_graph.dart';
 
-/// An [AssetReader] which ignores deleted files.
-class FinalizedReader implements AssetReader, AssetReaderState {
-  @override
+/// A view of the build output.
+///
+/// If [canRead] returns false, [unreadableReason] explains why the file is
+/// missing; for example, it might say that generation failed.
+class FinalizedReader {
   late final AssetFinder assetFinder = FunctionAssetFinder(_findAssets);
 
   final AssetReader _delegate;
@@ -38,12 +40,6 @@ class FinalizedReader implements AssetReader, AssetReaderState {
   FinalizedReader(this._delegate, this._assetGraph, this._targetGraph,
       this._buildPhases, this._rootPackage);
 
-  @override
-  AssetPathProvider? get assetPathProvider => _delegate.assetPathProvider;
-
-  @override
-  InputTracker? get inputTracker => _delegate.inputTracker;
-
   /// Returns a reason why [id] is not readable, or null if it is readable.
   Future<UnreadableReason?> unreadableReason(AssetId id) async {
     if (!_assetGraph.contains(id)) return UnreadableReason.notFound;
@@ -62,28 +58,20 @@ class FinalizedReader implements AssetReader, AssetReaderState {
     return UnreadableReason.unknown;
   }
 
-  @override
   Future<bool> canRead(AssetId id) async =>
       (await unreadableReason(id)) == null;
 
-  @override
   Future<Digest> digest(AssetId id) => _delegate.digest(id);
 
-  @override
   Future<List<int>> readAsBytes(AssetId id) => _delegate.readAsBytes(id);
 
-  @override
   Future<String> readAsString(AssetId id, {Encoding encoding = utf8}) async {
     if (_assetGraph.get(id)?.isDeleted ?? true) {
       throw AssetNotFoundException(id);
     }
     return _delegate.readAsString(id, encoding: encoding);
   }
 
-// This is only for generators, so only `BuildStep` needs to implement it.
-  @override
-  Stream<AssetId> findAssets(Glob glob_) => throw UnimplementedError();
-
   Stream<AssetId> _findAssets(Glob glob, String? _) async* {
     var potentialNodes = _assetGraph
         .packageNodes(_rootPackage)