Flutter tool support for automatic saving of JIT compilation trace (#25301)

packages/flutter/lib/src/foundation/binding.dart

@@ -6,6 +6,7 @@ import 'dart:async';
 import 'dart:convert' show json;
 import 'dart:developer' as developer;
 import 'dart:io' show exit;
+import 'dart:ui' show dumpCompilationTrace;
 
 import 'package:meta/meta.dart';
 
@@ -117,6 +118,14 @@ abstract class BindingBase {
         name: 'exit',
         callback: _exitApplication,
       );
+      registerServiceExtension(
+        name: 'dumpCompilationTrace',
+        callback: (Map<String, String> parameters) async {
+          return <String, dynamic> {
+            'value': dumpCompilationTrace(),
+          };
+        }
+      );
     }
 
     assert(() {

packages/flutter/test/foundation/service_extensions_test.dart

@@ -527,6 +527,15 @@ void main() {
     expect(binding.frameScheduled, isFalse);
   });
 
+  test('Service extensions - dumpCompilationTrace', () async {
+    Map<String, dynamic> result;
+    result = await binding.testExtension('dumpCompilationTrace', <String, String>{});
+    final String trace = String.fromCharCodes(result['value']);
+    expect(trace, contains('dart:core,Object,Object.\n'));
+    expect(trace, contains('package:test_api/test_api.dart,::,test\n'));
+    expect(trace, contains('service_extensions_test.dart,::,main\n'));
+  });
+
   test('Service extensions - posttest', () async {
     // See widget_inspector_test.dart for tests of the ext.flutter.inspector
     // service extensions included in this count.
@@ -539,7 +548,7 @@ void main() {
 
     // If you add a service extension... TEST IT! :-)
     // ...then increment this number.
-    expect(binding.extensions.length, 23 + widgetInspectorExtensionCount);
+    expect(binding.extensions.length, 24 + widgetInspectorExtensionCount);
 
     expect(console, isEmpty);
     debugPrint = debugPrintThrottled;

packages/flutter_tools/lib/src/commands/run.dart

@@ -33,6 +33,18 @@ abstract class RunCommandBase extends FlutterCommand {
       ..addOption('route',
         help: 'Which route to load when running the app.',
       )
+      ..addFlag('save-compilation-trace',
+        hide: !verboseHelp,
+        negatable: false,
+        help: 'Save runtime compilation trace to a file.\n'
+              'Compilation trace will be saved to compilation.txt when \'flutter run\' exits. '
+              'This file contains a list of Dart symbols that were compiled by the runtime JIT '
+              'compiler up to that point. This file can be used in later --dynamic builds to '
+              'precompile some code by the offline compiler, thus reducing application startup '
+              'latency at the cost of larger application package.\n'
+              'This flag is only allowed when running --dynamic --profile (recommended) or '
+              '--debug mode.\n'
+      )
       ..addOption('target-platform',
         defaultsTo: 'default',
         allowed: <String>['default', 'android-arm', 'android-arm64'],
@@ -318,6 +330,11 @@ class RunCommand extends RunCommandBase {
       }
     }
 
+    if (argResults['save-compilation-trace'] &&
+        getBuildMode() != BuildMode.debug && getBuildMode() != BuildMode.dynamicProfile)
+      throwToolExit('Error: --save-compilation-trace is only allowed when running '
+          '--dynamic --profile (recommended) or --debug mode.');
+
     final List<FlutterDevice> flutterDevices = devices.map<FlutterDevice>((Device device) {
       return FlutterDevice(
         device,
@@ -343,6 +360,7 @@ class RunCommand extends RunCommandBase {
         projectRootPath: argResults['project-root'],
         packagesFilePath: globalResults['packages'],
         dillOutputPath: argResults['output-dill'],
+        saveCompilationTrace: argResults['save-compilation-trace'],
         stayResident: stayResident,
         ipv6: ipv6,
       );
@@ -355,6 +373,7 @@ class RunCommand extends RunCommandBase {
         applicationBinary: applicationBinaryPath == null
             ? null
             : fs.file(applicationBinaryPath),
+        saveCompilationTrace: argResults['save-compilation-trace'],
         stayResident: stayResident,
         ipv6: ipv6,
       );

packages/flutter_tools/lib/src/resident_runner.dart

@@ -426,6 +426,7 @@ abstract class ResidentRunner {
     this.usesTerminalUI = true,
     String projectRootPath,
     String packagesFilePath,
+    this.saveCompilationTrace,
     this.stayResident,
     this.ipv6,
   }) {
@@ -440,6 +441,7 @@ abstract class ResidentRunner {
   final String target;
   final DebuggingOptions debuggingOptions;
   final bool usesTerminalUI;
+  final bool saveCompilationTrace;
   final bool stayResident;
   final bool ipv6;
   final Completer<int> _finished = Completer<int>();
@@ -487,6 +489,8 @@ abstract class ResidentRunner {
 
   Future<void> stop() async {
     _stopped = true;
+    if (saveCompilationTrace)
+      await _saveCompilationTrace();
     await stopEchoingDeviceLog();
     await preStop();
     return stopApp();
@@ -591,6 +595,35 @@ abstract class ResidentRunner {
     }
   }
 
+  Future<void> _saveCompilationTrace() async {
+    if (!supportsServiceProtocol)
+      return;
+
+    for (FlutterDevice device in flutterDevices) {
+      for (FlutterView view in device.views) {
+        final int index = device.views.indexOf(view);
+        printStatus('Saving compilation trace for '
+            '${device.device.name}${index == 0 ? '' :'/Isolate$index'}...');
+
+        List<int> buffer;
+        try {
+          buffer = await view.uiIsolate.flutterDumpCompilationTrace();
+          assert(buffer != null);
+        } catch (error) {
+          printError('Error communicating with Flutter on the device: $error');
+          continue;
+        }
+
+        final File outputFile = fs.currentDirectory
+          .childFile('compilation${index == 0 ? '' : index}.txt');
+
+        outputFile.parent.createSync(recursive: true);
+        outputFile.writeAsBytesSync(buffer);
+        printStatus('Compilation trace written to ${fs.path.relative(outputFile.path)}.');
+      }
+    }
+  }
+
   Future<void> _debugTogglePlatform() async {
     await refreshViews();
     final String from = await flutterDevices[0].views[0].uiIsolate.flutterPlatformOverride();

packages/flutter_tools/lib/src/run_cold.dart

@@ -21,12 +21,14 @@ class ColdRunner extends ResidentRunner {
     bool usesTerminalUI = true,
     this.traceStartup = false,
     this.applicationBinary,
+    bool saveCompilationTrace = false,
     bool stayResident = true,
     bool ipv6 = false,
   }) : super(devices,
              target: target,
              debuggingOptions: debuggingOptions,
              usesTerminalUI: usesTerminalUI,
+             saveCompilationTrace: saveCompilationTrace,
              stayResident: stayResident,
              ipv6: ipv6);
 

packages/flutter_tools/lib/src/run_hot.dart

@@ -61,6 +61,7 @@ class HotRunner extends ResidentRunner {
     String projectRootPath,
     String packagesFilePath,
     this.dillOutputPath,
+    bool saveCompilationTrace = false,
     bool stayResident = true,
     bool ipv6 = false,
   }) : super(devices,
@@ -69,6 +70,7 @@ class HotRunner extends ResidentRunner {
              usesTerminalUI: usesTerminalUI,
              projectRootPath: projectRootPath,
              packagesFilePath: packagesFilePath,
+             saveCompilationTrace: saveCompilationTrace,
              stayResident: stayResident,
              ipv6: ipv6);
 

packages/flutter_tools/lib/src/vmservice.dart

@@ -1312,6 +1312,14 @@ class Isolate extends ServiceObjectOwner {
     );
   }
 
+  Future<List<int>> flutterDumpCompilationTrace() async {
+    final Map<String, dynamic> result =
+      await invokeFlutterExtensionRpcRaw('ext.flutter.dumpCompilationTrace');
+    if (result != null && result['value'] is List<dynamic>)
+        return result['value'].cast<int>();
+    return null;
+  }
+
   // Application control extension methods.
   Future<Map<String, dynamic>> flutterExit() {
     return invokeFlutterExtensionRpcRaw(