Migrate tracing to null safety (#92849)

packages/flutter_tools/lib/src/tracing.dart

@@ -2,11 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:async';
 
-import 'package:meta/meta.dart';
 import 'package:vm_service/vm_service.dart' as vm_service;
 
 import 'base/common.dart';
@@ -24,8 +21,8 @@ const String kFirstFrameRasterizedEventName = 'Rasterized first useful frame';
 
 class Tracing {
   Tracing({
-    @required this.vmService,
-    @required Logger logger,
+    required this.vmService,
+    required Logger logger,
   }) : _logger = logger;
 
   static const String firstUsefulFrameEventName = kFirstFrameRasterizedEventName;
@@ -39,7 +36,7 @@ class Tracing {
   }
 
   /// Stops tracing; optionally wait for first frame.
-  Future<Map<String, dynamic>> stopTracingAndDownloadTimeline({
+  Future<Map<String, Object?>> stopTracingAndDownloadTimeline({
     bool awaitFirstFrame = false,
   }) async {
     if (awaitFirstFrame) {
@@ -62,9 +59,10 @@ class Tracing {
         bool done = false;
         final List<FlutterView> views = await vmService.getFlutterViews();
         for (final FlutterView view in views) {
-          if (await vmService
+          final String? uiIsolateId = view.uiIsolate?.id;
+          if (uiIsolateId != null && await vmService
               .flutterAlreadyPaintedFirstUsefulFrame(
-                isolateId: view.uiIsolate.id,
+                isolateId: uiIsolateId,
               )) {
             done = true;
             break;
@@ -80,14 +78,15 @@ class Tracing {
       }
       status.stop();
     }
-    final vm_service.Response timeline = await vmService.getTimeline();
+    final vm_service.Response? timeline = await vmService.getTimeline();
     await vmService.setTimelineFlags(<String>[]);
-    if (timeline == null) {
+    final Map<String, Object?>? timelineJson = timeline?.json;
+    if (timelineJson == null) {
       throwToolExit(
         'The device disconnected before the timeline could be retrieved.',
       );
     }
-    return timeline.json;
+    return timelineJson;
   }
 }
 
@@ -95,8 +94,8 @@ class Tracing {
 /// store it to `$output/start_up_info.json`.
 Future<void> downloadStartupTrace(FlutterVmService vmService, {
   bool awaitFirstFrame = true,
-  @required Logger logger,
-  @required Directory output,
+  required Logger logger,
+  required Directory output,
 }) async {
   final File traceInfoFile = output.childFile('start_up_info.json');
 
@@ -110,33 +109,39 @@ Future<void> downloadStartupTrace(FlutterVmService vmService, {
 
   final Tracing tracing = Tracing(vmService: vmService, logger: logger);
 
-  final Map<String, dynamic> timeline = await tracing.stopTracingAndDownloadTimeline(
+  final Map<String, Object?> timeline = await tracing.stopTracingAndDownloadTimeline(
     awaitFirstFrame: awaitFirstFrame,
   );
 
   final File traceTimelineFile = output.childFile('start_up_timeline.json');
   traceTimelineFile.writeAsStringSync(toPrettyJson(timeline));
 
-  int extractInstantEventTimestamp(String eventName) {
-    final List<Map<String, dynamic>> events =
-        List<Map<String, dynamic>>.from(timeline['traceEvents'] as List<dynamic>);
-    final Map<String, dynamic> event = events.firstWhere(
-      (Map<String, dynamic> event) => event['name'] == eventName, orElse: () => null,
-    );
-    return event == null ? null : (event['ts'] as int);
+  int? extractInstantEventTimestamp(String eventName) {
+    final List<Object?>? traceEvents = timeline['traceEvents'] as List<Object?>?;
+    if (traceEvents == null) {
+      return null;
+    }
+    final List<Map<String, Object?>> events = List<Map<String, Object?>>.from(traceEvents);
+    Map<String, Object?>? matchedEvent;
+    for (final Map<String, Object?> event in events) {
+      if (event['name'] == eventName) {
+        matchedEvent = event;
+      }
+    }
+    return matchedEvent == null ? null : (matchedEvent['ts'] as int?);
   }
 
   String message = 'No useful metrics were gathered.';
 
-  final int engineEnterTimestampMicros = extractInstantEventTimestamp(kFlutterEngineMainEnterEventName);
-  final int frameworkInitTimestampMicros = extractInstantEventTimestamp(kFrameworkInitEventName);
+  final int? engineEnterTimestampMicros = extractInstantEventTimestamp(kFlutterEngineMainEnterEventName);
+  final int? frameworkInitTimestampMicros = extractInstantEventTimestamp(kFrameworkInitEventName);
 
   if (engineEnterTimestampMicros == null) {
     logger.printTrace('Engine start event is missing in the timeline: $timeline');
     throwToolExit('Engine start event is missing in the timeline. Cannot compute startup time.');
   }
 
-  final Map<String, dynamic> traceInfo = <String, dynamic>{
+  final Map<String, Object?> traceInfo = <String, Object?>{
     'engineEnterTimestampMicros': engineEnterTimestampMicros,
   };
 
@@ -147,8 +152,8 @@ Future<void> downloadStartupTrace(FlutterVmService vmService, {
   }
 
   if (awaitFirstFrame) {
-    final int firstFrameBuiltTimestampMicros = extractInstantEventTimestamp(kFirstFrameBuiltEventName);
-    final int firstFrameRasterizedTimestampMicros = extractInstantEventTimestamp(kFirstFrameRasterizedEventName);
+    final int? firstFrameBuiltTimestampMicros = extractInstantEventTimestamp(kFirstFrameBuiltEventName);
+    final int? firstFrameRasterizedTimestampMicros = extractInstantEventTimestamp(kFirstFrameRasterizedEventName);
     if (firstFrameBuiltTimestampMicros == null || firstFrameRasterizedTimestampMicros == null) {
       logger.printTrace('First frame events are missing in the timeline: $timeline');
       throwToolExit('First frame events are missing in the timeline. Cannot compute startup time.');

packages/flutter_tools/lib/src/vmservice.dart

@@ -402,7 +402,7 @@ class FlutterView {
     required this.uiIsolate,
   });
 
-  factory FlutterView.parse(Map<String, Object> json) {
+  factory FlutterView.parse(Map<String, Object?> json) {
     final Map<String, Object?>? rawIsolate = json['isolate'] as Map<String, Object?>?;
     vm_service.IsolateRef? isolate;
     if (rawIsolate != null) {
@@ -822,11 +822,11 @@ class FlutterVmService {
         // with cleaning up.
         return <FlutterView>[];
       }
-      final List<Object>? rawViews = response.json?['views'] as List<Object>?;
+      final List<Object?>? rawViews = response.json?['views'] as List<Object?>?;
       final List<FlutterView> views = <FlutterView>[
         if (rawViews != null)
-          for (final Object rawView in rawViews)
-            FlutterView.parse(rawView as Map<String, Object>)
+          for (final Map<String, Object?> rawView in rawViews.whereType<Map<String, Object?>>())
+            FlutterView.parse(rawView)
       ];
       if (views.isNotEmpty || returnEarly) {
         return views;

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

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -90,19 +88,19 @@ void main() {
             vm_service.TimelineEvent.parse(<String, Object>{
               'name': kFlutterEngineMainEnterEventName,
               'ts': 0,
-            }),
+            })!,
             vm_service.TimelineEvent.parse(<String, Object>{
               'name': kFrameworkInitEventName,
               'ts': 1,
-            }),
+            })!,
             vm_service.TimelineEvent.parse(<String, Object>{
               'name': kFirstFrameBuiltEventName,
               'ts': 2,
-            }),
+            })!,
             vm_service.TimelineEvent.parse(<String, Object>{
               'name': kFirstFrameRasterizedEventName,
               'ts': 3,
-            }),
+            })!,
           ],
         ).toJson(),
       ),
@@ -197,11 +195,11 @@ void main() {
             vm_service.TimelineEvent.parse(<String, Object>{
               'name': kFlutterEngineMainEnterEventName,
               'ts': 0,
-            }),
+            })!,
             vm_service.TimelineEvent.parse(<String, Object>{
               'name': kFrameworkInitEventName,
               'ts': 1,
-            }),
+            })!,
           ],
         ).toJson(),
       ),
@@ -232,11 +230,11 @@ void main() {
             vm_service.TimelineEvent.parse(<String, Object>{
               'name': kFlutterEngineMainEnterEventName,
               'ts': 0,
-            }),
+            })!,
             vm_service.TimelineEvent.parse(<String, Object>{
               'name': kFrameworkInitEventName,
               'ts': 1,
-            }),
+            })!,
           ],
         ).toJson(),
       ),
@@ -277,19 +275,19 @@ void main() {
             vm_service.TimelineEvent.parse(<String, Object>{
               'name': kFlutterEngineMainEnterEventName,
               'ts': 0,
-            }),
+            })!,
             vm_service.TimelineEvent.parse(<String, Object>{
               'name': kFrameworkInitEventName,
               'ts': 1,
-            }),
+            })!,
             vm_service.TimelineEvent.parse(<String, Object>{
               'name': kFirstFrameBuiltEventName,
               'ts': 2,
-            }),
+            })!,
             vm_service.TimelineEvent.parse(<String, Object>{
               'name': kFirstFrameRasterizedEventName,
               'ts': 3,
-            }),
+            })!,
           ],
         ).toJson(),
       ),
@@ -310,25 +308,25 @@ void main() {
       logger: logger,
     );
 
-    final Map<String, dynamic> expectedTimeline = <String, dynamic>{
+    final Map<String, Object> expectedTimeline = <String, Object>{
       'type': 'Timeline',
-      'traceEvents': <dynamic>[
-        <String, dynamic>{
+      'traceEvents': <Object>[
+        <String, Object>{
           'name': 'FlutterEngineMainEnter',
           'ts': 0,
           'type': 'TimelineEvent',
         },
-        <String, dynamic>{
+        <String, Object>{
           'name': 'Framework initialization',
           'ts': 1,
           'type': 'TimelineEvent',
         },
-        <String, dynamic>{
+        <String, Object>{
           'name': 'Widgets built first useful frame',
           'ts': 2,
           'type': 'TimelineEvent',
         },
-        <String, dynamic>{
+        <String, Object>{
           'name': 'Rasterized first useful frame',
           'ts': 3,
           'type': 'TimelineEvent',

packages/flutter_tools/test/src/fake_vm_services.dart

@@ -26,14 +26,14 @@ class FakeVmServiceHost {
     ), httpAddress: httpAddress, wsAddress: wsAddress);
     _applyStreamListen();
     _output.stream.listen((String data) {
-      final Map<String, Object> request = json.decode(data) as Map<String, Object>;
+      final Map<String, Object?> request = json.decode(data) as Map<String, Object?>;
       if (_requests.isEmpty) {
         throw Exception('Unexpected request: $request');
       }
       final FakeVmServiceRequest fakeRequest = _requests.removeAt(0) as FakeVmServiceRequest;
-      expect(request, isA<Map<String, Object>>()
-        .having((Map<String, Object> request) => request['method'], 'method', fakeRequest.method)
-        .having((Map<String, Object> request) => request['params'], 'args', fakeRequest.args)
+      expect(request, isA<Map<String, Object?>>()
+        .having((Map<String, Object?> request) => request['method'], 'method', fakeRequest.method)
+        .having((Map<String, Object?> request) => request['params'], 'args', fakeRequest.args)
       );
       if (fakeRequest.close) {
         unawaited(_vmService.dispose());
@@ -52,6 +52,7 @@ class FakeVmServiceHost {
           'id': request['id'],
           'error': <String, Object?>{
             'code': fakeRequest.errorCode,
+            'message': 'error',
           }
         }));
       }
@@ -108,7 +109,7 @@ class FakeVmServiceRequest implements VmServiceExpectation {
   /// standard response.
   final int? errorCode;
   final Map<String, Object>? args;
-  final Map<String, Object>? jsonResponse;
+  final Map<String, Object?>? jsonResponse;
 
   @override
   bool get isRequest => true;