Fix pre-existing output deletion. (#4058)

Author: davidmorgan

build_runner/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Bug fix: fix corner case with checked in generated output that could cause
   a crash.
+- Bug fix: during initial build cleanup, really delete files that correspond
+  to hidden generated files.
 
 ## 2.5.2
 

build_runner_core/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Bug fix: fix corner case with checked in generated output that could cause
   a crash.
+- Bug fix: during initial build cleanup, really delete files that correspond
+  to hidden generated files.
 
 ## 9.1.0
 

build_runner_core/lib/src/generate/build_definition.dart

@@ -7,8 +7,6 @@ import 'dart:io';
 
 import 'package:build/build.dart';
 // ignore: implementation_imports
-import 'package:build/src/internal.dart';
-// ignore: implementation_imports
 import 'package:build_runner/src/internal.dart';
 import 'package:watcher/watcher.dart';
 
@@ -167,10 +165,10 @@ class _Loader {
       }
 
       buildLog.doing('Doing initial build cleanup.');
-      await _initialBuildCleanup(
-        conflictingOutputs,
-        _environment.writer.copyWith(generatedAssetHider: assetGraph),
-      );
+      // Use a writer with no asset graph. If it had the asset graph, it would
+      // delete from the generated output location, but the aim is to delete
+      // from input sources.
+      await _initialBuildCleanup(conflictingOutputs, _environment.writer);
     }
 
     return BuildDefinition._(

build_test/pubspec.yaml

@@ -12,7 +12,7 @@ dependencies:
   build: ^2.5.0
   build_config: ^1.0.0
   build_resolvers: ^2.5.0
-  build_runner_core: ^9.1.0
+  build_runner_core: ^9.1.1-wip
   convert: ^3.0.0
   crypto: ^3.0.0
   glob: ^2.0.0

build_test/test/test_builder_test.dart

@@ -344,6 +344,18 @@ Future<void> main() async {
       {AssetId('a', 'bar.other')},
     );
   });
+
+  test('pre-existing output is replaced by new generated output', () {
+    return testBuilder(
+      TestBuilder(
+        buildExtensions: {
+          '.in': ['.out'],
+        },
+      ),
+      {'a|foo.in': 'new input', 'a|foo.out': 'pre-existing output'},
+      outputs: {'a|foo.out': 'new input'},
+    );
+  });
 }
 
 /// Concatenates the contents of multiple text files into a single output.