[flutter_tools] default tree-shake-icons to enabled and improve performance (flutter#54923)

Author: jonahwilliams

dev/benchmarks/macrobenchmarks/pubspec.yaml

@@ -16,6 +16,7 @@ dependencies:
   # and run
   #   flutter update-packages --force-upgrade
   flutter_gallery_assets: 0.1.9+2
+  cupertino_icons: 0.1.3
 
   archive: 2.0.13 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   args: 1.6.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
@@ -91,4 +92,4 @@ flutter:
   - packages/flutter_gallery_assets/food/cherry_pie.png
   - assets/999x1000.png
 
-# PUBSPEC CHECKSUM: 3a55
+# PUBSPEC CHECKSUM: 49fa

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

@@ -60,9 +60,9 @@ Future<Depfile> copyAssets(Environment environment, Directory outputDirectory) a
         file.parent.createSync(recursive: true);
         final DevFSContent content = entry.value;
         if (content is DevFSFileContent && content.file is File) {
-          inputs.add(globals.fs.file(content.file.path));
+          inputs.add(content.file as File);
           if (!await iconTreeShaker.subsetFont(
-            inputPath: content.file.path,
+            input: content.file as File,
             outputPath: file.path,
             relativePath: entry.key,
           )) {

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

@@ -4,6 +4,7 @@
 
 import 'package:meta/meta.dart';
 import 'package:process/process.dart';
+import 'package:mime/mime.dart' as mime;
 
 import '../../artifacts.dart';
 import '../../base/common.dart';
@@ -20,7 +21,7 @@ import 'dart.dart';
 const String kIconTreeShakerFlag = 'TreeShakeIcons';
 
 /// Whether icon font subsetting is enabled by default.
-const bool kIconTreeShakerEnabledDefault = false;
+const bool kIconTreeShakerEnabledDefault = true;
 
 List<Map<String, dynamic>> _getList(dynamic object, String errorMessage) {
   try {
@@ -66,6 +67,12 @@ class IconTreeShaker {
     }
   }
 
+  /// The MIME type for ttf fonts.
+  static const Set<String> kTtfMimeTypes = <String>{
+    'font/ttf', // based on internet search
+    'application/x-font-ttf', // based on running locally.
+  };
+
   /// The [Source] inputs that targets using this should depend on.
   ///
   /// See [Target.inputs].
@@ -77,6 +84,7 @@ class IconTreeShaker {
 
   final Environment _environment;
   final String _fontManifest;
+  Future<void> _iconDataProcessing;
   Map<String, _IconTreeShakerData> _iconData;
 
   final ProcessManager _processManager;
@@ -89,10 +97,10 @@ class IconTreeShaker {
                    && _environment.defines[kIconTreeShakerFlag] == 'true'
                    && _environment.defines[kBuildMode] != 'debug';
 
-  /// Fills the [_iconData] map.
-  Future<Map<String, _IconTreeShakerData>> _getIconData(Environment environment) async {
+  // Fills the [_iconData] map.
+  Future<void> _getIconData(Environment environment) async {
     if (!enabled) {
-      return null;
+      return;
     }
 
     final File appDill = environment.buildDir.childFile('app.dill');
@@ -135,13 +143,11 @@ class IconTreeShaker {
         codePoints: iconData[entry.key],
       );
     }
-    return result;
+    _iconData = result;
   }
 
-  /// Calls font-subset, which transforms the `inputPath` font file to a
-  /// subsetted version at `outputPath`.
-  ///
-  /// The `relativePath` parameter
+  /// Calls font-subset, which transforms the [input] font file to a
+  /// subsetted version at [outputPath].
   ///
   /// All parameters are required.
   ///
@@ -150,15 +156,24 @@ class IconTreeShaker {
   /// If the font-subset subprocess fails, it will [throwToolExit].
   /// Otherwise, it will return true.
   Future<bool> subsetFont({
-    @required String inputPath,
+    @required File input,
     @required String outputPath,
     @required String relativePath,
   }) async {
     if (!enabled) {
       return false;
     }
-
-    _iconData ??= await _getIconData(_environment);
+    if (input.lengthSync() < 12) {
+      return false;
+    }
+    final String mimeType = mime.lookupMimeType(
+      input.path,
+      headerBytes: await input.openRead(0, 12).first,
+    );
+    if (!kTtfMimeTypes.contains(mimeType)) {
+      return false;
+    }
+    await (_iconDataProcessing ??= _getIconData(_environment));
     assert(_iconData != null);
 
     final _IconTreeShakerData iconTreeShakerData = _iconData[relativePath];
@@ -176,7 +191,7 @@ class IconTreeShaker {
     final List<String> cmd = <String>[
       fontSubset.path,
       outputPath,
-      inputPath,
+      input.path,
     ];
     final String codePoints = iconTreeShakerData.codePoints.join(' ');
     _logger.printTrace('Running font-subset: ${cmd.join(' ')}, '
@@ -186,9 +201,7 @@ class IconTreeShaker {
       fontSubsetProcess.stdin.writeln(codePoints);
       await fontSubsetProcess.stdin.flush();
       await fontSubsetProcess.stdin.close();
-    } on Exception catch (_) {
-      // handled by checking the exit code.
-    } on OSError catch (_) {  // ignore: dead_code_on_catch_subtype
+    } on Exception {
       // handled by checking the exit code.
     }
 

packages/flutter_tools/test/commands.shard/permeable/build_bundle_test.dart

@@ -219,7 +219,7 @@ void main() {
         kBuildMode: 'debug',
         kTargetPlatform: 'android-arm',
         kTrackWidgetCreation: 'true',
-        kIconTreeShakerFlag: null,
+        kIconTreeShakerFlag: 'true',
       });
 
       return BuildResult(success: true);