Add lint 'discarded_futures'.

analysis_options.yaml

@@ -67,6 +67,7 @@ linter:
     # - constant_identifier_names # https://github.com/dart-lang/linter/issues/204
     - control_flow_in_finally
     - directives_ordering
+    - discarded_futures
     - empty_catches
     - empty_constructor_bodies
     - empty_statements

case_study/memory_leaks/memory_leak_app/lib/main.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 
 import 'about.dart';
@@ -86,15 +88,19 @@ class MyHomeState extends State<MyHome> with SingleTickerProviderStateMixin {
   void showMenuSelection(String value) {
     switch (value) {
       case logMenu:
-        Navigator.push(
-          context,
-          MaterialPageRoute(builder: (context) => Logger()),
+        unawaited(
+          Navigator.push(
+            context,
+            MaterialPageRoute(builder: (context) => Logger()),
+          ),
         );
         break;
       case aboutMenu:
-        Navigator.push(
-          context,
-          MaterialPageRoute(builder: (context) => About()),
+        unawaited(
+          Navigator.push(
+            context,
+            MaterialPageRoute(builder: (context) => About()),
+          ),
         );
         break;
       default:

case_study/memory_leaks/memory_leak_app/lib/tabs/http_data.dart

@@ -144,6 +144,6 @@ class MyGetHttpDataState extends State<MyGetHttpData> {
     super.initState();
 
     // Call the getJSONData() method when the app initializes
-    getJSONData();
+    unawaited(getJSONData());
   }
 }

case_study/memory_leaks/memory_leak_app/lib/tabs/logger.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 
 import '../common.dart';
@@ -34,31 +36,33 @@ class LoggerState extends State<Logger> {
 
   // ignore: unused_element
   void _pushSaved() {
-    Navigator.of(context).push(
-      MaterialPageRoute(
-        builder: (context) {
-          final tiles = _saved.map(
-            (itemValue) {
-              return ListTile(
-                title: Text(
-                  itemValue,
-                  style: _biggerFont,
-                ),
-              );
-            },
-          );
-          final divided = ListTile.divideTiles(
-            context: context,
-            tiles: tiles,
-          ).toList();
+    unawaited(
+      Navigator.of(context).push(
+        MaterialPageRoute(
+          builder: (context) {
+            final tiles = _saved.map(
+              (itemValue) {
+                return ListTile(
+                  title: Text(
+                    itemValue,
+                    style: _biggerFont,
+                  ),
+                );
+              },
+            );
+            final divided = ListTile.divideTiles(
+              context: context,
+              tiles: tiles,
+            ).toList();
 
-          return Scaffold(
-            appBar: AppBar(
-              title: const Text('Saved lists'),
-            ),
-            body: ListView(children: divided),
-          );
-        },
+            return Scaffold(
+              appBar: AppBar(
+                title: const Text('Saved lists'),
+              ),
+              body: ListView(children: divided),
+            );
+          },
+        ),
       ),
     );
   }

case_study/memory_leaks/memory_leak_app/lib/tabs/settings.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 
 import '../logging.dart';
@@ -61,9 +63,11 @@ class SettingsState extends State<Settings> {
                 restfulApi = key;
               });
               // Display the data received.
-              Navigator.push(
-                context,
-                MaterialPageRoute(builder: (context) => MyGetHttpData()),
+              unawaited(
+                Navigator.push(
+                  context,
+                  MaterialPageRoute(builder: (context) => MyGetHttpData()),
+                ),
               );
             },
           );

case_study/platform_channel/lib/channel_demo.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 
@@ -14,7 +16,7 @@ class _ChannelDemoState extends State<ChannelDemo> {
   late String _response;
 
   void _sendMessage() {
-    _channel.send('Message from Dart');
+    unawaited(_channel.send('Message from Dart'));
   }
 
   void _reset() {

case_study/platform_channel/lib/main.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 
 import 'channel_demo.dart';
@@ -30,9 +32,11 @@ class _HomePage extends StatelessWidget {
         child: TextButton(
           style: TextButton.styleFrom(backgroundColor: Colors.green),
           onPressed: () {
-            Navigator.push(
-              context,
-              MaterialPageRoute(builder: (context) => ChannelDemo()),
+            unawaited(
+              Navigator.push(
+                context,
+                MaterialPageRoute(builder: (context) => ChannelDemo()),
+              ),
             );
           },
           child: const Text(

packages/devtools_app/lib/src/analytics/analytics_controller.dart

@@ -24,7 +24,7 @@ class AnalyticsController {
   })  : _analyticsEnabled = ValueNotifier<bool>(enabled),
         _shouldPrompt = ValueNotifier<bool>(firstRun && !enabled) {
     if (_shouldPrompt.value) {
-      toggleAnalyticsEnabled(true);
+      unawaited(toggleAnalyticsEnabled(true));
     }
     if (_analyticsEnabled.value) {
       setUpAnalytics();

packages/devtools_app/lib/src/analytics/prompt.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 
@@ -105,9 +107,11 @@ class _AnalyticsPromptState extends State<AnalyticsPrompt>
                 textTheme.titleMedium?.copyWith(color: const Color(0xFF54C1EF)),
             recognizer: TapGestureRecognizer()
               ..onTap = () {
-                launchUrl(
-                  'https://www.google.com/intl/en/policies/privacy',
-                  context,
+                unawaited(
+                  launchUrl(
+                    'https://www.google.com/intl/en/policies/privacy',
+                    context,
+                  ),
                 );
               },
           ),
@@ -127,7 +131,7 @@ class _AnalyticsPromptState extends State<AnalyticsPrompt>
         ElevatedButton(
           onPressed: () {
             // This will also hide the prompt.
-            controller.toggleAnalyticsEnabled(false);
+            unawaited(controller.toggleAnalyticsEnabled(false));
           },
           style: ElevatedButton.styleFrom(backgroundColor: Colors.grey),
           child: const Text('No thanks.'),
@@ -137,9 +141,8 @@ class _AnalyticsPromptState extends State<AnalyticsPrompt>
         ),
         ElevatedButton(
           onPressed: () {
-            controller
-              ..toggleAnalyticsEnabled(true)
-              ..hidePrompt();
+            unawaited(controller.toggleAnalyticsEnabled(true));
+            controller.hidePrompt();
           },
           child: const Text('Sounds good!'),
         ),

packages/devtools_app/lib/src/app.dart

@@ -104,7 +104,7 @@ class DevToolsAppState extends State<DevToolsApp> with AutoDisposeMixin {
   void initState() {
     super.initState();
 
-    ga.setupDimensions();
+    unawaited(ga.setupDimensions());
 
     addAutoDisposeListener(serviceManager.isolateManager.mainIsolate, () {
       setState(() {

packages/devtools_app/lib/src/charts/flame_chart.dart

@@ -392,22 +392,30 @@ abstract class FlameChartState<T extends FlameChart,
       // TODO(kenz): zoom in/out faster if key is held. It actually zooms slower
       // if the key is held currently.
       if (keyLabel == 'w') {
-        zoomTo(
-          math.min(
-            maxZoomLevel,
-            currentZoom + keyboardZoomInUnit,
+        unawaited(
+          zoomTo(
+            math.min(
+              maxZoomLevel,
+              currentZoom + keyboardZoomInUnit,
+            ),
           ),
         );
       } else if (keyLabel == 's') {
-        zoomTo(
-          math.max(
-            FlameChart.minZoomLevel,
-            currentZoom - keyboardZoomOutUnit,
+        unawaited(
+          zoomTo(
+            math.max(
+              FlameChart.minZoomLevel,
+              currentZoom - keyboardZoomOutUnit,
+            ),
           ),
         );
       } else if (keyLabel == 'a') {
+        // `unawaited` does not work for FutureOr
+        // ignore: discarded_futures
         scrollToX(horizontalControllerGroup.offset - keyboardScrollUnit);
       } else if (keyLabel == 'd') {
+        // `unawaited` does not work for FutureOr
+        // ignore: discarded_futures
         scrollToX(horizontalControllerGroup.offset + keyboardScrollUnit);
       }
     }
@@ -478,6 +486,8 @@ abstract class FlameChartState<T extends FlameChart,
       // to call this that guarantees the scroll controller offsets will be
       // updated for the new zoom level and layout size
       // https://github.com/flutter/devtools/issues/2012.
+      // `unawaited` does not work for FutureOr
+      // ignore: discarded_futures
       scrollToX(newScrollOffset, jump: true);
     });
   }

packages/devtools_app/lib/src/config_specific/drag_and_drop/_drag_and_drop_web.dart

@@ -32,9 +32,9 @@ class DragAndDropManagerWeb extends DragAndDropManager {
 
   @override
   void dispose() {
-    onDragOverSubscription.cancel();
-    onDragLeaveSubscription.cancel();
-    onDropSubscription.cancel();
+    unawaited(onDragOverSubscription.cancel());
+    unawaited(onDragLeaveSubscription.cancel());
+    unawaited(onDropSubscription.cancel());
     super.dispose();
   }
 

packages/devtools_app/lib/src/example/conditional_screen.dart

@@ -55,7 +55,7 @@ class _ExampleConditionalScreenBodyState
       final json =
           offlineController.offlineDataJson[ExampleConditionalScreen.id];
       if (json.isNotEmpty) {
-        loadOfflineData(json['title']);
+        unawaited(loadOfflineData(json['title']));
       }
     }
   }

packages/devtools_app/lib/src/framework/initializer.dart

@@ -77,7 +77,7 @@ class _InitializerState extends State<Initializer>
           !connectionState.userInitiatedConnectionState) {
         // Try to reconnect (otherwise, will fall back to showing the
         // disconnected overlay).
-        _attemptUrlConnection();
+        unawaited(_attemptUrlConnection());
       }
     });
 
@@ -88,7 +88,7 @@ class _InitializerState extends State<Initializer>
       serviceManager.onConnectionAvailable.listen((_) => setState(() {})),
     );
 
-    _attemptUrlConnection();
+    unawaited(_attemptUrlConnection());
   }
 
   @override
@@ -97,7 +97,7 @@ class _InitializerState extends State<Initializer>
 
     // Handle widget rebuild when the URL has changed.
     if (widget.url != null && widget.url != oldWidget.url) {
-      _attemptUrlConnection();
+      unawaited(_attemptUrlConnection());
     }
   }
 

packages/devtools_app/lib/src/framework/landing_screen.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+
 import 'package:devtools_shared/devtools_shared.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
@@ -158,7 +160,8 @@ class _ConnectDialogState extends State<ConnectDialog>
             SizedBox(
               width: scaleByFontFactor(350.0),
               child: TextField(
-                onSubmitted: actionInProgress ? null : (str) => _connect(),
+                onSubmitted:
+                    actionInProgress ? null : (str) => unawaited(_connect()),
                 autofocus: true,
                 decoration: const InputDecoration(
                   isDense: true,
@@ -265,7 +268,7 @@ class ImportFileInstructions extends StatelessWidget {
           ),
           const SizedBox(height: defaultSpacing),
           ElevatedButton(
-            onPressed: () => _importFile(context),
+            onPressed: () => unawaited(_importFile(context)),
             child: const MaterialIconLabel(
               label: 'Import File',
               iconData: Icons.file_upload,

packages/devtools_app/lib/src/framework/release_notes/release_notes.dart

@@ -166,7 +166,8 @@ class ReleaseNotes extends AnimatedWidget {
                 : Expanded(
                     child: Markdown(
                       data: markdownData!,
-                      onTapLink: (_, href, __) => launchUrl(href!, context),
+                      onTapLink: (_, href, __) =>
+                          unawaited(launchUrl(href!, context)),
                     ),
                   ),
           ],

packages/devtools_app/lib/src/http/http_request_data.dart

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
 import 'dart:convert';
 import 'dart:typed_data';
 
@@ -44,7 +45,7 @@ class DartIOHttpRequestData extends NetworkRequest {
   })  : wrapperId = _dartIoHttpRequestWrapperId++,
         super(timelineMicrosBase) {
     if (requestFullDataFromVmService && _request.isResponseComplete) {
-      getFullRequestData();
+      unawaited(getFullRequestData());
     }
   }