refactor asset bundle code to not depend on the global Cache.flutterRoot (#142277)

Fixes https://github.com/flutter/flutter/issues/142285.

Part of work on https://github.com/flutter/flutter/pull/141194.

This is a refactor. There should be no changes in tool behavior.

packages/flutter_tools/lib/src/asset.dart

@@ -64,7 +64,12 @@ abstract class AssetBundleFactory {
     required FileSystem fileSystem,
     required Platform platform,
     bool splitDeferredAssets = false,
-  }) => _ManifestAssetBundleFactory(logger: logger, fileSystem: fileSystem, platform: platform, splitDeferredAssets: splitDeferredAssets);
+  }) => _ManifestAssetBundleFactory(
+    logger: logger,
+    fileSystem: fileSystem,
+    platform: platform,
+    splitDeferredAssets: splitDeferredAssets,
+  );
 
   /// Creates a new [AssetBundle].
   AssetBundle createBundle();
@@ -138,7 +143,13 @@ class _ManifestAssetBundleFactory implements AssetBundleFactory {
   final bool _splitDeferredAssets;
 
   @override
-  AssetBundle createBundle() => ManifestAssetBundle(logger: _logger, fileSystem: _fileSystem, platform: _platform, splitDeferredAssets: _splitDeferredAssets);
+  AssetBundle createBundle() => ManifestAssetBundle(
+    logger: _logger,
+    fileSystem: _fileSystem,
+    platform: _platform,
+    flutterRoot: Cache.flutterRoot!,
+    splitDeferredAssets: _splitDeferredAssets,
+  );
 }
 
 /// An asset bundle based on a pubspec.yaml file.
@@ -149,10 +160,12 @@ class ManifestAssetBundle implements AssetBundle {
     required Logger logger,
     required FileSystem fileSystem,
     required Platform platform,
+    required String flutterRoot,
     bool splitDeferredAssets = false,
   }) : _logger = logger,
        _fileSystem = fileSystem,
        _platform = platform,
+       _flutterRoot = flutterRoot,
        _splitDeferredAssets = splitDeferredAssets,
        _licenseCollector = LicenseCollector(fileSystem: fileSystem);
 
@@ -160,6 +173,7 @@ class ManifestAssetBundle implements AssetBundle {
   final FileSystem _fileSystem;
   final LicenseCollector _licenseCollector;
   final Platform _platform;
+  final String _flutterRoot;
   final bool _splitDeferredAssets;
 
   @override
@@ -584,7 +598,7 @@ class ManifestAssetBundle implements AssetBundle {
         final Uri entryUri = _fileSystem.path.toUri(asset);
         result.add(_Asset(
           baseDir: _fileSystem.path.join(
-            Cache.flutterRoot!,
+            _flutterRoot,
             'bin', 'cache', 'artifacts', 'material_fonts',
           ),
           relativeUri: Uri(path: entryUri.pathSegments.last),
@@ -600,8 +614,7 @@ class ManifestAssetBundle implements AssetBundle {
 
   List<_Asset> _getMaterialShaders() {
     final String shaderPath = _fileSystem.path.join(
-      Cache.flutterRoot!,
-      'packages', 'flutter', 'lib', 'src', 'material', 'shaders',
+      _flutterRoot, 'packages', 'flutter', 'lib', 'src', 'material', 'shaders',
     );
     // This file will exist in a real invocation unless the git checkout is
     // corrupted somehow, but unit tests generally don't create this file

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

@@ -368,6 +368,11 @@ flutter:
           logger: logger,
           fileSystem: testFileSystem,
           platform: platform,
+          flutterRoot: Cache.defaultFlutterRoot(
+            platform: platform,
+            fileSystem: testFileSystem,
+            userMessages: UserMessages(),
+          ),
           splitDeferredAssets: true,
         );
 
@@ -379,15 +384,6 @@ flutter:
         return bundle;
       }
 
-      late String? previousCacheFlutterRootValue;
-
-      setUp(() {
-        previousCacheFlutterRootValue = Cache.flutterRoot;
-        Cache.flutterRoot = Cache.defaultFlutterRoot(platform: platform, fileSystem: testFileSystem, userMessages: UserMessages());
-      });
-
-      tearDown(() => Cache.flutterRoot = previousCacheFlutterRootValue);
-
       testWithoutContext('correctly bundles assets given a simple asset manifest with flavors', () async {
         testFileSystem.file('.packages').createSync();
         testFileSystem.file(testFileSystem.path.join('assets', 'common', 'image.png')).createSync(recursive: true);

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

@@ -42,14 +42,15 @@ void main() {
   group('AssetBundle asset variants (with Unix-style paths)', () {
     late Platform platform;
     late FileSystem fs;
+    late String flutterRoot;
 
     setUp(() {
       platform = FakePlatform();
       fs = MemoryFileSystem.test();
-      Cache.flutterRoot = Cache.defaultFlutterRoot(
+      flutterRoot = Cache.defaultFlutterRoot(
         platform: platform,
         fileSystem: fs,
-        userMessages: UserMessages()
+        userMessages: UserMessages(),
       );
 
       fs.file('.packages').createSync();
@@ -94,6 +95,7 @@ ${assets.map((String entry) => '    - $entry').join('\n')}
         logger: BufferLogger.test(),
         fileSystem: fs,
         platform: platform,
+        flutterRoot: flutterRoot,
       );
 
       await bundle.build(
@@ -147,6 +149,7 @@ ${assets.map((String entry) => '    - $entry').join('\n')}
       final ManifestAssetBundle bundle = ManifestAssetBundle(
         logger: BufferLogger.test(),
         fileSystem: fs,
+        flutterRoot: flutterRoot,
         platform: platform,
       );
 
@@ -203,6 +206,7 @@ ${assets.map((String entry) => '    - $entry').join('\n')}
         logger: BufferLogger.test(),
         fileSystem: fs,
         platform: platform,
+        flutterRoot: flutterRoot,
       );
 
       await bundle.build(
@@ -248,6 +252,7 @@ ${assets.map((String entry) => '    - $entry').join('\n')}
         logger: BufferLogger.test(),
         fileSystem: fs,
         platform: platform,
+        flutterRoot: flutterRoot,
       );
 
       await bundle.build(
@@ -274,11 +279,12 @@ ${assets.map((String entry) => '    - $entry').join('\n')}
   group('AssetBundle asset variants (with Windows-style filepaths)', () {
     late final Platform platform;
     late final FileSystem fs;
+    late final String flutterRoot;
 
     setUp(() {
       platform = FakePlatform(operatingSystem: 'windows');
       fs = MemoryFileSystem.test(style: FileSystemStyle.windows);
-      Cache.flutterRoot = Cache.defaultFlutterRoot(
+      flutterRoot = Cache.defaultFlutterRoot(
         platform: platform,
         fileSystem: fs,
         userMessages: UserMessages()
@@ -318,6 +324,7 @@ flutter:
         logger: BufferLogger.test(),
         fileSystem: fs,
         platform: platform,
+        flutterRoot: flutterRoot,
       );
 
       await bundle.build(

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

@@ -26,16 +26,8 @@ void main() {
     group('Assets (${style.name} file system)', () {
       late FileSystem fileSystem;
       late BufferLogger logger;
-      late String? previousCacheFlutterRootValue;
       late Platform platform;
-
-      setUpAll(() {
-        previousCacheFlutterRootValue = Cache.flutterRoot;
-      });
-
-      tearDownAll(() {
-        Cache.flutterRoot = previousCacheFlutterRootValue;
-      });
+      late String flutterRoot;
 
       setUp(() {
         fileSystem = MemoryFileSystem(
@@ -44,7 +36,7 @@ void main() {
         logger = BufferLogger.test();
         platform = FakePlatform(
             operatingSystem: style == Style.posix ? 'linux' : 'windows');
-        Cache.flutterRoot = Cache.defaultFlutterRoot(
+        flutterRoot = Cache.defaultFlutterRoot(
           platform: platform,
           fileSystem: fileSystem,
           userMessages: UserMessages(),
@@ -60,6 +52,7 @@ void main() {
           fileSystem: fileSystem,
           platform: platform,
           splitDeferredAssets: true,
+          flutterRoot: flutterRoot,
         );
 
         fileSystem.file(fileSystem.path.join('font', 'pubspec.yaml'))
@@ -157,6 +150,7 @@ dependencies:
           fileSystem: fileSystem,
           platform: platform,
           splitDeferredAssets: true,
+          flutterRoot: flutterRoot,
         );
 
         await assetBundle.build(
@@ -175,7 +169,7 @@ dependencies:
       testWithoutContext('bundles material shaders on non-web platforms',
           () async {
         final String shaderPath = fileSystem.path.join(
-          Cache.flutterRoot!,
+          flutterRoot,
           'packages',
           'flutter',
           'lib',
@@ -205,6 +199,7 @@ dependencies:
           logger: logger,
           fileSystem: fileSystem,
           platform: platform,
+          flutterRoot: flutterRoot,
         );
 
         await assetBundle.build(
@@ -219,7 +214,7 @@ dependencies:
       testWithoutContext('bundles material shaders on web platforms',
           () async {
         final String shaderPath = fileSystem.path.join(
-          Cache.flutterRoot!,
+          flutterRoot,
           'packages',
           'flutter',
           'lib',
@@ -249,6 +244,7 @@ dependencies:
           logger: logger,
           fileSystem: fileSystem,
           platform: platform,
+          flutterRoot: flutterRoot,
         );
 
         await assetBundle.build(