Extra timing on hot reload (#104242)

This PR adds extra timings for a hot reload.
As an example, before a user might see

> Performing hot reload...                                                
> Reloaded 1 of 788 libraries in 554ms.

With this PR it would instead be something like

> Performing hot reload...                                                
> Reloaded 1 of 788 libraries in 554ms (compile: 33 ms, reload: 153 ms, reassemble: 310 ms).

packages/flutter_tools/lib/src/resident_runner.dart

@@ -1486,7 +1486,7 @@ abstract class ResidentRunner extends ResidentHandlers {
 }
 
 class OperationResult {
-  OperationResult(this.code, this.message, { this.fatal = false, this.updateFSReport });
+  OperationResult(this.code, this.message, { this.fatal = false, this.updateFSReport, this.extraTimings = const <OperationResultExtraTiming>[] });
 
   /// The result of the operation; a non-zero code indicates a failure.
   final int code;
@@ -1494,6 +1494,9 @@ class OperationResult {
   /// A user facing message about the results of the operation.
   final String message;
 
+  /// User facing extra timing information about the operation.
+  final List<OperationResultExtraTiming> extraTimings;
+
   /// Whether this error should cause the runner to exit.
   final bool fatal;
 
@@ -1504,6 +1507,16 @@ class OperationResult {
   static final OperationResult ok = OperationResult(0, '');
 }
 
+class OperationResultExtraTiming {
+  const OperationResultExtraTiming(this.description, this.timeInMs);
+
+  /// A user facing short description of this timing.
+  final String description;
+
+  /// The time this operation took in milliseconds.
+  final int timeInMs;
+}
+
 Future<String> getMissingPackageHintForPlatform(TargetPlatform platform) async {
   switch (platform) {
     case TargetPlatform.android_arm:

packages/flutter_tools/lib/src/run_hot.dart

@@ -726,9 +726,16 @@ class HotRunner extends ResidentRunner {
     if (result.isOk) {
       final String elapsed = getElapsedAsMilliseconds(timer.elapsed);
       if (!silent) {
+        if (result.extraTimings.isNotEmpty) {
+          final String extraTimingsString = result.extraTimings
+            .map((OperationResultExtraTiming e) => '${e.description}: ${e.timeInMs} ms')
+            .join(', ');
+          globals.printStatus('${result.message} in $elapsed ($extraTimingsString).');
+        } else {
           globals.printStatus('${result.message} in $elapsed.');
         }
       }
+    }
     return result;
   }
 
@@ -898,6 +905,10 @@ class HotRunner extends ResidentRunner {
     if (!updatedDevFS.success) {
       return OperationResult(1, 'DevFS synchronization failed');
     }
+
+    final List<OperationResultExtraTiming> extraTimings = <OperationResultExtraTiming>[];
+    extraTimings.add(OperationResultExtraTiming('compile', updatedDevFS.compileDuration.inMilliseconds));
+
     String reloadMessage = 'Reloaded 0 libraries';
     final Stopwatch reloadVMTimer = _stopwatchFactory.createStopwatch('reloadSources:vm')..start();
     final Map<String, Object> firstReloadDetails = <String, Object>{};
@@ -920,6 +931,7 @@ class HotRunner extends ResidentRunner {
       _addBenchmarkData('hotReloadVMReloadMilliseconds', 0);
     }
     reloadVMTimer.stop();
+    extraTimings.add(OperationResultExtraTiming('reload', reloadVMTimer.elapsedMilliseconds));
 
     await evictDirtyAssets();
 
@@ -939,6 +951,7 @@ class HotRunner extends ResidentRunner {
     // Record time it took for Flutter to reassemble the application.
     reassembleTimer.stop();
     _addBenchmarkData('hotReloadFlutterReassembleMilliseconds', reassembleTimer.elapsed.inMilliseconds);
+    extraTimings.add(OperationResultExtraTiming('reassemble', reassembleTimer.elapsedMilliseconds));
 
     reloadTimer.stop();
     final Duration reloadDuration = reloadTimer.elapsed;
@@ -985,6 +998,7 @@ class HotRunner extends ResidentRunner {
     return OperationResult(
       reassembleResult.failedReassemble ? 1 : OperationResult.ok.code,
       reloadMessage,
+      extraTimings: extraTimings
     );
   }
 

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

@@ -846,6 +846,95 @@ void main() {
     FeatureFlags: () => TestFeatureFlags(isSingleWidgetReloadEnabled: true),
   }));
 
+  testUsingContext('ResidentRunner reports hot reload time details', () => testbed.run(() async {
+    fakeVmServiceHost = FakeVmServiceHost(requests: <VmServiceExpectation>[
+      listViews,
+      FakeVmServiceRequest(
+        method: 'getVM',
+        jsonResponse: fakeVM.toJson(),
+      ),
+      listViews,
+      listViews,
+      FakeVmServiceRequest(
+        method: 'getVM',
+        jsonResponse: fakeVM.toJson(),
+      ),
+      const FakeVmServiceRequest(
+        method: 'reloadSources',
+        args: <String, Object>{
+          'isolateId': '1',
+          'pause': false,
+          'rootLibUri': 'main.dart.incremental.dill',
+        },
+        jsonResponse: <String, Object>{
+          'type': 'ReloadReport',
+          'success': true,
+          'details': <String, Object>{
+            'loadedLibraryCount': 1,
+            'finalLibraryCount': 42,
+          },
+        },
+      ),
+      FakeVmServiceRequest(
+        method: 'getIsolate',
+        args: <String, Object>{
+          'isolateId': '1',
+        },
+        jsonResponse: fakeUnpausedIsolate.toJson(),
+      ),
+      FakeVmServiceRequest(
+        method: 'ext.flutter.fastReassemble',
+        args: <String, Object>{
+          'isolateId': fakeUnpausedIsolate.id,
+          'className': 'FOO',
+        },
+      ),
+    ]);
+    final FakeDelegateFlutterDevice flutterDevice = FakeDelegateFlutterDevice(
+      device,
+      BuildInfo.debug,
+      FakeResidentCompiler(),
+      devFS,
+    )..vmService = fakeVmServiceHost.vmService;
+    residentRunner = HotRunner(
+      <FlutterDevice>[
+        flutterDevice,
+      ],
+      stayResident: false,
+      debuggingOptions: DebuggingOptions.enabled(BuildInfo.debug),
+      target: 'main.dart',
+      devtoolsHandler: createNoOpHandler,
+    );
+    devFS.nextUpdateReport = UpdateFSReport(
+      success: true,
+      fastReassembleClassName: 'FOO',
+      invalidatedSourcesCount: 1,
+    );
+
+    final Completer<DebugConnectionInfo> futureConnectionInfo = Completer<DebugConnectionInfo>.sync();
+    final Completer<void> futureAppStart = Completer<void>.sync();
+    unawaited(residentRunner.attach(
+      appStartedCompleter: futureAppStart,
+      connectionInfoCompleter: futureConnectionInfo,
+      enableDevTools: true,
+    ));
+
+    await futureAppStart.future;
+    await residentRunner.restart();
+
+    // The actual test: Expect to have compile, reload and reassemble times.
+    expect(
+        testLogger.statusText,
+        contains(RegExp(r'Reloaded 1 of 42 libraries in \d+ms '
+            r'\(compile: \d+ ms, reload: \d+ ms, reassemble: \d+ ms\)\.')));
+  }, overrides: <Type, Generator>{
+    FileSystem: () => MemoryFileSystem.test(),
+    Platform: () => FakePlatform(),
+    ProjectFileInvalidator: () => FakeProjectFileInvalidator(),
+    Usage: () => TestUsage(),
+    FeatureFlags: () => TestFeatureFlags(isSingleWidgetReloadEnabled: true),
+  }));
+
   testUsingContext('ResidentRunner can send target platform to analytics from full restart', () => testbed.run(() async {
     fakeVmServiceHost = FakeVmServiceHost(requests: <VmServiceExpectation>[
       listViews,

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

@@ -375,7 +375,7 @@ void main() {
             return null;
           }),
           Barrier('Performing hot reload...'.padRight(progressMessageWidth), logging: true),
-          Multiple(<Pattern>[RegExp(r'^Reloaded 0 libraries in [0-9]+ms\.$'), 'called reassemble', 'called paint'], handler: (String line) {
+          Multiple(<Pattern>[RegExp(r'^Reloaded 0 libraries in [0-9]+ms \(compile: \d+ ms, reload: \d+ ms, reassemble: \d+ ms\)\.$'), 'called reassemble', 'called paint'], handler: (String line) {
             processManager.killPid(pid, ProcessSignal.sigusr2);
             return null;
           }),