[flutter_tools] never tree shake 0x20 (space) font codepoints on web (#128302)

Always pass the space code point (`0x20`) to the font subsetter when targetting web because the web engine relies on that character to calculate a font's height.

Fixes #127270

packages/flutter_tools/lib/src/build_system/targets/assets.dart

@@ -78,6 +78,7 @@ Future<Depfile> copyAssets(
     logger: environment.logger,
     fileSystem: environment.fileSystem,
     artifacts: environment.artifacts,
+    targetPlatform: targetPlatform,
   );
   final ShaderCompiler shaderCompiler = ShaderCompiler(
     processManager: environment.processManager,

packages/flutter_tools/lib/src/build_system/targets/icon_tree_shaker.dart

@@ -42,11 +42,13 @@ class IconTreeShaker {
     required Logger logger,
     required FileSystem fileSystem,
     required Artifacts artifacts,
+    required TargetPlatform targetPlatform,
   }) : _processManager = processManager,
        _logger = logger,
        _fs = fileSystem,
        _artifacts = artifacts,
-       _fontManifest = fontManifest?.string {
+       _fontManifest = fontManifest?.string,
+       _targetPlatform = targetPlatform {
     if (_environment.defines[kIconTreeShakerFlag] == 'true' &&
         _environment.defines[kBuildMode] == 'debug') {
       logger.printError('Font subsetting is not supported in debug mode. The '
@@ -82,6 +84,7 @@ class IconTreeShaker {
   final Logger _logger;
   final FileSystem _fs;
   final Artifacts _artifacts;
+  final TargetPlatform _targetPlatform;
 
   /// Whether font subsetting should be used for this [Environment].
   bool get enabled => _fontManifest != null
@@ -129,11 +132,17 @@ class IconTreeShaker {
     }
 
     final Map<String, _IconTreeShakerData> result = <String, _IconTreeShakerData>{};
+    const int kSpacePoint = 32;
     for (final MapEntry<String, String> entry in fonts.entries) {
       final List<int>? codePoints = iconData[entry.key];
       if (codePoints == null) {
         throw IconTreeShakerException._('Expected to font code points for ${entry.key}, but none were found.');
       }
+      if (_targetPlatform == TargetPlatform.web_javascript) {
+        if (!codePoints.contains(kSpacePoint)) {
+          codePoints.add(kSpacePoint);
+        }
+      }
       result[entry.value] = _IconTreeShakerData(
         family: entry.key,
         relativePath: entry.value,
@@ -155,7 +164,6 @@ class IconTreeShaker {
     required String outputPath,
     required String relativePath,
   }) async {
-
     if (!enabled) {
       return false;
     }

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

@@ -21,6 +21,8 @@ const String inputPath = '/input/fonts/MaterialIcons-Regular.otf';
 const String outputPath = '/output/fonts/MaterialIcons-Regular.otf';
 const String relativePath = 'fonts/MaterialIcons-Regular.otf';
 
+final RegExp whitespace = RegExp(r'\s+');
+
 void main() {
   late BufferLogger logger;
   late MemoryFileSystem fileSystem;
@@ -122,6 +124,7 @@ void main() {
       processManager: processManager,
       fileSystem: fileSystem,
       artifacts: artifacts,
+      targetPlatform: TargetPlatform.android,
     );
 
     expect(
@@ -153,6 +156,7 @@ void main() {
       processManager: processManager,
       fileSystem: fileSystem,
       artifacts: artifacts,
+      targetPlatform: TargetPlatform.android,
     );
 
     expect(
@@ -176,6 +180,7 @@ void main() {
       processManager: processManager,
       fileSystem: fileSystem,
       artifacts: artifacts,
+      targetPlatform: TargetPlatform.android,
     );
 
     expect(
@@ -199,6 +204,7 @@ void main() {
       processManager: processManager,
       fileSystem: fileSystem,
       artifacts: artifacts,
+      targetPlatform: TargetPlatform.android,
     );
 
     expect(
@@ -227,6 +233,7 @@ void main() {
       processManager: processManager,
       fileSystem: fileSystem,
       artifacts: artifacts,
+      targetPlatform: TargetPlatform.android,
     );
     final CompleterIOSink stdinSink = CompleterIOSink();
     addConstFinderInvocation(appDill.path, stdout: validConstFinderResult);
@@ -276,6 +283,7 @@ void main() {
       processManager: processManager,
       fileSystem: fileSystem,
       artifacts: artifacts,
+      targetPlatform: TargetPlatform.android,
     );
 
     final CompleterIOSink stdinSink = CompleterIOSink();
@@ -308,6 +316,7 @@ void main() {
       processManager: processManager,
       fileSystem: fileSystem,
       artifacts: artifacts,
+      targetPlatform: TargetPlatform.android,
     );
 
     final CompleterIOSink stdinSink = CompleterIOSink();
@@ -341,6 +350,7 @@ void main() {
         processManager: processManager,
         fileSystem: fileSystem,
         artifacts: artifacts,
+        targetPlatform: platform,
       );
 
       addConstFinderInvocation(appDill.path, stdout: constFinderResultWithInvalid);
@@ -360,6 +370,97 @@ void main() {
       expect(processManager, hasNoRemainingExpectations);
     });
   }
+
+  testWithoutContext('Does not add 0x32 for non-web builds', () async {
+    final Environment environment = createEnvironment(<String, String>{
+      kIconTreeShakerFlag: 'true',
+      kBuildMode: 'release',
+    });
+    final File appDill = environment.buildDir.childFile('app.dill')
+      ..createSync(recursive: true);
+
+    final IconTreeShaker iconTreeShaker = IconTreeShaker(
+      environment,
+      fontManifestContent,
+      logger: logger,
+      processManager: processManager,
+      fileSystem: fileSystem,
+      artifacts: artifacts,
+      targetPlatform: TargetPlatform.android_arm64,
+    );
+
+    addConstFinderInvocation(
+      appDill.path,
+      // Does not contain space char
+      stdout: validConstFinderResult,
+    );
+    final CompleterIOSink stdinSink = CompleterIOSink();
+    resetFontSubsetInvocation(stdinSink: stdinSink);
+    expect(processManager.hasRemainingExpectations, isTrue);
+    final File inputFont = fileSystem.file(inputPath)
+        ..writeAsBytesSync(List<int>.filled(2500, 0));
+    fileSystem.file(outputPath)
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(List<int>.filled(1200, 0));
+
+    final bool result = await iconTreeShaker.subsetFont(
+      input: inputFont,
+      outputPath: outputPath,
+      relativePath: relativePath,
+    );
+
+    expect(result, isTrue);
+    final List<String> codePoints = stdinSink.getAndClear().trim().split(whitespace);
+    expect(codePoints, isNot(contains('32')));
+
+    expect(processManager, hasNoRemainingExpectations);
+  });
+
+  testWithoutContext('Ensures 0x32 is included for web builds', () async {
+    final Environment environment = createEnvironment(<String, String>{
+      kIconTreeShakerFlag: 'true',
+      kBuildMode: 'release',
+    });
+    final File appDill = environment.buildDir.childFile('app.dill')
+      ..createSync(recursive: true);
+
+    final IconTreeShaker iconTreeShaker = IconTreeShaker(
+      environment,
+      fontManifestContent,
+      logger: logger,
+      processManager: processManager,
+      fileSystem: fileSystem,
+      artifacts: artifacts,
+      targetPlatform: TargetPlatform.web_javascript,
+    );
+
+    addConstFinderInvocation(
+      appDill.path,
+      // Does not contain space char
+      stdout: validConstFinderResult,
+    );
+    final CompleterIOSink stdinSink = CompleterIOSink();
+    resetFontSubsetInvocation(stdinSink: stdinSink);
+    expect(processManager.hasRemainingExpectations, isTrue);
+    final File inputFont = fileSystem.file(inputPath)
+        ..writeAsBytesSync(List<int>.filled(2500, 0));
+    fileSystem.file(outputPath)
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(List<int>.filled(1200, 0));
+
+    final bool result = await iconTreeShaker.subsetFont(
+      input: inputFont,
+      outputPath: outputPath,
+      relativePath: relativePath,
+    );
+
+    expect(result, isTrue);
+    final List<String> codePoints = stdinSink.getAndClear().trim().split(whitespace);
+    expect(codePoints, containsAllInOrder(const <String>['59470', '32']));
+
+    expect(processManager, hasNoRemainingExpectations);
+  });
+
   testWithoutContext('Non-zero font-subset exit code', () async {
     final Environment environment = createEnvironment(<String, String>{
       kIconTreeShakerFlag: 'true',
@@ -376,6 +477,7 @@ void main() {
       processManager: processManager,
       fileSystem: fileSystem,
       artifacts: artifacts,
+      targetPlatform: TargetPlatform.android,
     );
 
     final CompleterIOSink stdinSink = CompleterIOSink();
@@ -408,6 +510,7 @@ void main() {
       processManager: processManager,
       fileSystem: fileSystem,
       artifacts: artifacts,
+      targetPlatform: TargetPlatform.android,
     );
 
     final CompleterIOSink stdinSink = CompleterIOSink(throwOnAdd: true);
@@ -442,6 +545,7 @@ void main() {
       processManager: processManager,
       fileSystem: fileSystem,
       artifacts: artifacts,
+      targetPlatform: TargetPlatform.android,
     );
 
     addConstFinderInvocation(appDill.path, stdout: validConstFinderResult);
@@ -474,6 +578,7 @@ void main() {
       processManager: processManager,
       fileSystem: fileSystem,
       artifacts: artifacts,
+      targetPlatform: TargetPlatform.android,
     );
 
     addConstFinderInvocation(appDill.path, exitCode: -1);