refactor: strip all local symbols from macOS and iOS App.framework - reduces app size (#111264)

packages/flutter_tools/lib/src/base/build.dart

@@ -162,7 +162,7 @@ class AOTSnapshotter {
     }
 
     final String assembly = _fileSystem.path.join(outputDir.path, 'snapshot_assembly.S');
-    if (platform == TargetPlatform.ios || platform == TargetPlatform.darwin) {
+    if (targetingApplePlatform) {
       genSnapshotArgs.addAll(<String>[
         '--snapshot_kind=app-aot-assembly',
         '--assembly=$assembly',
@@ -181,7 +181,7 @@ class AOTSnapshotter {
     if (targetingApplePlatform) {
       stripAfterBuild = shouldStrip;
       if (stripAfterBuild) {
-        _logger.printTrace('Will strip AOT snapshot manual after build and dSYM generation.');
+        _logger.printTrace('Will strip AOT snapshot manually after build and dSYM generation.');
       }
     } else {
       stripAfterBuild = false;
@@ -331,7 +331,7 @@ class AOTSnapshotter {
 
       if (stripAfterBuild) {
         // See https://www.unix.com/man-page/osx/1/strip/ for arguments
-        final RunResult stripResult = await _xcode.strip(<String>['-S', appLib, '-o', appLib]);
+        final RunResult stripResult = await _xcode.strip(<String>['-x', appLib, '-o', appLib]);
         if (stripResult.exitCode != 0) {
           _logger.printError('Failed to strip debugging symbols from the generated AOT snapshot - strip terminated with exit code ${stripResult.exitCode}');
           return stripResult.exitCode;

packages/flutter_tools/test/general.shard/base/build_test.dart

@@ -262,7 +262,7 @@ void main() {
         const FakeCommand(command: <String>[
           'xcrun',
           'strip',
-          '-S',
+          '-x',
           'build/foo/App.framework/App',
           '-o',
           'build/foo/App.framework/App',
@@ -335,7 +335,7 @@ void main() {
         const FakeCommand(command: <String>[
           'xcrun',
           'strip',
-          '-S',
+          '-x',
           'build/foo/App.framework/App',
           '-o',
           'build/foo/App.framework/App',
@@ -407,7 +407,7 @@ void main() {
         const FakeCommand(command: <String>[
           'xcrun',
           'strip',
-          '-S',
+          '-x',
           'build/foo/App.framework/App',
           '-o',
           'build/foo/App.framework/App',
@@ -476,7 +476,7 @@ void main() {
         const FakeCommand(command: <String>[
           'xcrun',
           'strip',
-          '-S',
+          '-x',
           'build/foo/App.framework/App',
           '-o',
           'build/foo/App.framework/App',

packages/flutter_tools/test/general.shard/build_system/targets/common_test.dart

@@ -529,7 +529,7 @@ void main() {
       FakeCommand(command: <String>[
         'xcrun',
         'strip',
-        '-S',
+        '-x',
         '$build/arm64/App.framework/App',
         '-o',
         '$build/arm64/App.framework/App',
@@ -619,7 +619,7 @@ void main() {
       FakeCommand(command: <String>[
         'xcrun',
         'strip',
-        '-S',
+        '-x',
         '$build/arm64/App.framework/App',
         '-o',
         '$build/arm64/App.framework/App',

packages/flutter_tools/test/general.shard/build_system/targets/macos_test.dart

@@ -503,7 +503,7 @@ void main() {
       FakeCommand(command: <String>[
         'xcrun',
         'strip',
-        '-S',
+        '-x',
         environment.buildDir.childFile('arm64/App.framework/App').path,
         '-o',
         environment.buildDir.childFile('arm64/App.framework/App').path,
@@ -511,7 +511,7 @@ void main() {
       FakeCommand(command: <String>[
         'xcrun',
         'strip',
-        '-S',
+        '-x',
         environment.buildDir.childFile('x86_64/App.framework/App').path,
         '-o',
         environment.buildDir.childFile('x86_64/App.framework/App').path,

packages/flutter_tools/test/host_cross_arch.shard/ios_content_validation_test.dart

@@ -193,37 +193,28 @@ void main() {
         });
 
         testWithoutContext('check symbols', () {
-          final ProcessResult symbols = processManager.runSync(
-            <String>[
-              'nm',
-              '-g',
-              outputAppFrameworkBinary.path,
-              '-arch',
-              'arm64',
-            ],
-          );
-          final bool aotSymbolsFound = (symbols.stdout as String).contains('_kDartVmSnapshot');
-          expect(aotSymbolsFound, buildMode != BuildMode.debug);
+          final List<String> symbols =
+              AppleTestUtils.getExportedSymbols(outputAppFrameworkBinary.path);
+          if (buildMode == BuildMode.debug) {
+            expect(symbols, isEmpty);
+          } else {
+            expect(symbols, equals(AppleTestUtils.requiredSymbols));
+          }
         });
 
-        // dSYM is not created for a debug build so nothing to check.
-        if (buildMode != BuildMode.debug) {
-          testWithoutContext('check symbols in dSYM', () {
-            final ProcessResult nm = processManager.runSync(
-              <String>[
-                'nm',
-                '--debug-syms',
-                '--defined-only',
-                '--just-symbol-name',
-                buildAppFrameworkDsymBinary.path,
-                '-arch',
-                'arm64',
-              ],
-            );
-            final List<String> symbols = (nm.stdout as String).split('\n');
-            expect(symbols, contains('_kDartVmSnapshotInstructions'));
-          });
-        }
+        testWithoutContext('check symbols in dSYM', () {
+          if (buildMode == BuildMode.debug) {
+            // dSYM is not created for a debug build.
+            expect(buildAppFrameworkDsymBinary.existsSync(), isFalse);
+          } else {
+            final List<String> symbols =
+                AppleTestUtils.getExportedSymbols(buildAppFrameworkDsymBinary.path);
+            expect(symbols, containsAll(AppleTestUtils.requiredSymbols));
+            // The actual number of symbols is going to vary but there should
+            // be "many" in the dSYM. At the time of writing, it was 7656.
+            expect(symbols.length, greaterThanOrEqualTo(5000));
+          }
+        });
 
         testWithoutContext('xcode_backend embed_and_thin', () {
           outputFlutterFramework.deleteSync(recursive: true);

packages/flutter_tools/test/host_cross_arch.shard/macos_content_validation_test.dart

@@ -87,19 +87,27 @@ void main() {
         'App.framework',
       ));
 
-      _checkFatBinary(
-        outputAppFramework.childFile('App'),
-        buildModeLower,
-        'dynamically linked shared library',
-      );
-
-      // dSYM is not created for a debug build so nothing to check.
-      if (buildMode != 'Debug') {
-        _checkFatBinary(
-          buildPath.childFile('App.framework.dSYM/Contents/Resources/DWARF/App'),
-          buildModeLower,
-          'dSYM companion file',
-        );
+      final File libBinary = outputAppFramework.childFile('App');
+      final File libDsymBinary =
+        buildPath.childFile('App.framework.dSYM/Contents/Resources/DWARF/App');
+
+      _checkFatBinary(libBinary, buildModeLower, 'dynamically linked shared library');
+
+      final List<String> libSymbols = AppleTestUtils.getExportedSymbols(libBinary.path);
+
+      if (buildMode == 'Debug') {
+        // dSYM is not created for a debug build.
+        expect(libDsymBinary.existsSync(), isFalse);
+        expect(libSymbols, isEmpty);
+      } else {
+        _checkFatBinary(libDsymBinary, buildModeLower, 'dSYM companion file');
+        expect(libSymbols, equals(AppleTestUtils.requiredSymbols));
+        final List<String> dSymSymbols =
+            AppleTestUtils.getExportedSymbols(libDsymBinary.path);
+        expect(dSymSymbols, containsAll(AppleTestUtils.requiredSymbols));
+        // The actual number of symbols is going to vary but there should
+        // be "many" in the dSYM. At the time of writing, it was 19195.
+        expect(dSymSymbols.length, greaterThanOrEqualTo(15000));
       }
 
       expect(outputAppFramework.childLink('Resources'), exists);

packages/flutter_tools/test/integration.shard/test_utils.dart

@@ -99,3 +99,31 @@ Future<void> pollForServiceExtensionValue<T>({
     " attempts responded with '$continuePollingValue'.",
   );
 }
+
+class AppleTestUtils {
+  // static only
+  AppleTestUtils._();
+
+  static const List<String> requiredSymbols = <String>[
+    '_kDartIsolateSnapshotData',
+    '_kDartIsolateSnapshotInstructions',
+    '_kDartVmSnapshotData',
+    '_kDartVmSnapshotInstructions'
+  ];
+
+  static List<String> getExportedSymbols(String dwarfPath) {
+    final ProcessResult nm = processManager.runSync(
+      <String>[
+        'nm',
+        '--debug-syms',  // nm docs: 'Show all symbols, even debugger only'
+        '--defined-only',
+        '--just-symbol-name',
+        dwarfPath,
+        '-arch',
+        'arm64',
+      ],
+    );
+    final String nmOutput = (nm.stdout as String).trim();
+    return nmOutput.isEmpty ? const <String>[] : nmOutput.split('\n');
+  }
+}