[tool] makes listing a shader also as an asset a build failure (#176866)

fixes #126829

Turns listing an asset as a `shader` and an `asset` a build error.

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Author: gaaclarke

packages/flutter_tools/lib/src/asset.dart

@@ -1070,6 +1070,26 @@ class ManifestAssetBundle implements AssetBundle {
     });
 
     for (final Uri shaderUri in flutterManifest.shaders) {
+      for (final AssetsEntry assetEntry in flutterManifest.assets) {
+        final String assetPath = assetEntry.uri.path;
+        final String shaderPath = shaderUri.path;
+        if (assetPath == shaderPath) {
+          _logger.printError(
+            'Error: Shader "$shaderPath" is also defined as an asset. Shaders '
+            'should only be defined in the "shaders" section of the '
+            'pubspec.yaml, not in the "assets" section.',
+          );
+          return null;
+        }
+        if (assetPath.endsWith('/') && shaderPath.startsWith(assetPath)) {
+          _logger.printError(
+            'Error: Shader "$shaderPath" is included in the asset directory '
+            '"$assetPath". Shaders should only be defined in the "shaders" '
+            'section of the pubspec.yaml, not in the "assets" section.',
+          );
+          return null;
+        }
+      }
       _parseAssetFromFile(
         packageConfig,
         flutterManifest,

packages/flutter_tools/test/general.shard/asset_test.dart

@@ -375,6 +375,66 @@ flutter:
           expect(assetBundle.entries.keys, contains('shaders/$shader'));
         }
       });
+
+      testWithoutContext('fails if shader is also in assets', () async {
+        writePackageConfigFiles(directory: fileSystem.currentDirectory, mainLibName: 'my_package');
+        fileSystem.file('pubspec.yaml').writeAsStringSync(r'''
+name: my_package
+flutter:
+  shaders:
+    - shaders/my_shader.frag
+  assets:
+    - shaders/my_shader.frag
+''');
+        fileSystem.file('shaders/my_shader.frag').createSync(recursive: true);
+        final assetBundle = ManifestAssetBundle(
+          logger: logger,
+          fileSystem: fileSystem,
+          platform: platform,
+          flutterRoot: flutterRoot,
+        );
+
+        final int result = await assetBundle.build(
+          packageConfigPath: '.dart_tool/package_config.json',
+          flutterProject: FlutterProject.fromDirectoryTest(fileSystem.currentDirectory),
+        );
+        expect(result, isNot(0));
+        expect(
+          logger.errorText,
+          contains('Error: Shader "shaders/my_shader.frag" is also defined as an asset.'),
+        );
+      });
+
+      testWithoutContext('fails if shader is in asset directory', () async {
+        writePackageConfigFiles(directory: fileSystem.currentDirectory, mainLibName: 'my_package');
+        fileSystem.file('pubspec.yaml').writeAsStringSync(r'''
+name: my_package
+flutter:
+  shaders:
+    - shaders/my_shader.frag
+  assets:
+    - shaders/
+''');
+        fileSystem.file('shaders/my_shader.frag').createSync(recursive: true);
+        final assetBundle = ManifestAssetBundle(
+          logger: logger,
+          fileSystem: fileSystem,
+          platform: platform,
+          flutterRoot: flutterRoot,
+        );
+
+        final int result = await assetBundle.build(
+          packageConfigPath: '.dart_tool/package_config.json',
+          flutterProject: FlutterProject.fromDirectoryTest(fileSystem.currentDirectory),
+        );
+        expect(result, isNot(0));
+        expect(
+          logger.errorText,
+          contains(
+            'Error: Shader "shaders/my_shader.frag" is included in the asset directory "shaders/".',
+          ),
+        );
+      });
     });
   }
 }