[various] Fixes unawaited_futures violations (flutter#4067)

This option had been disabled to match flutter/flutter, but the reason it was disabled there was "too many false positives", mostly around animation. That doesn't apply to most packages here, and we've had a number of production bugs�especially in plugins, that use async heavily in ways that are intended to be client-awaitable�that this would have caught.

This PR:
- Enables the option at the repo level.
- Permanently (unless the owners decide to change it) opts out `animations` and `go_router`, both of which looked like mostly or entirely false positives.
- Temporarily opted out a few plugins that have a lot of violations that should be handled in their own PRs later (`camera_android_camerax`, most of `webview_flutter`).
- Fixes all remaining violations.

In many cases this PR is behavior-changing, replacing implicitly unawaited futures that did not seem obviously intentional with `await`ed futures, so non-test code in particular should be reviewed carefully to make sure the changes are correct. All of the changes are manual, not `fix`-generated.

Part of flutter#127323

Author: stuartmorgan-g

analysis_options.yaml

@@ -183,7 +183,7 @@ linter:
     - tighten_type_of_initializing_formals
     # - type_annotate_public_apis # subset of always_specify_types
     - type_init_formals
-    # - unawaited_futures # too many false positives, especially with the way AnimationController works
+    - unawaited_futures # DIFFERENT FROM FLUTTER/FLUTTER: It's disabled there for "too many false positives"; that's not an issue here, and missing awaits have caused production issues in plugins.
     - unnecessary_await_in_return
     - unnecessary_brace_in_string_interps
     - unnecessary_const

packages/animations/analysis_options.yaml

@@ -0,0 +1,10 @@
+# This custom rule set only exists to allow opting out of the repository
+# default of enabling unawaited_futures. Please do NOT add more changes
+# here without consulting with #hackers-ecosystem on Discord.
+
+include: ../../analysis_options.yaml
+
+linter:
+  rules:
+    # Matches flutter/flutter, which disables this rule due to false positives.
+    unawaited_futures: false

packages/camera/camera/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.10.5+2
+
+* Fixes unawaited_futures violations.
+
 ## 0.10.5+1
 
 * Removes obsolete null checks on non-nullable values.

packages/camera/camera/lib/src/camera_controller.dart

@@ -552,7 +552,7 @@ class CameraController extends ValueNotifier<CameraValue> {
     }
 
     if (value.isStreamingImages) {
-      stopImageStream();
+      await stopImageStream();
     }
 
     try {

packages/camera/camera/pubspec.yaml

@@ -4,7 +4,7 @@ description: A Flutter plugin for controlling the camera. Supports previewing
   Dart.
 repository: https://github.com/flutter/packages/tree/main/packages/camera/camera
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+camera%22
-version: 0.10.5+1
+version: 0.10.5+2
 
 environment:
   sdk: ">=2.18.0 <4.0.0"

packages/camera/camera/test/camera_image_stream_test.dart

@@ -174,7 +174,7 @@ void main() {
 
     await cameraController.initialize();
 
-    cameraController.startVideoRecording(
+    await cameraController.startVideoRecording(
         onAvailable: (CameraImage image) => null);
 
     expect(
@@ -192,7 +192,7 @@ void main() {
 
     await cameraController.initialize();
 
-    cameraController.startVideoRecording();
+    await cameraController.startVideoRecording();
 
     expect(mockPlatform.streamCallLog.contains('startVideoCapturing'), isTrue);
   });

packages/camera/camera_android/CHANGELOG.md

@@ -1,3 +1,7 @@
+## NEXT
+
+* Fixes unawaited_futures violations.
+
 ## 0.10.8+2
 
 * Removes obsolete null checks on non-nullable values.

packages/camera/camera_android/example/lib/camera_controller.dart

@@ -229,12 +229,12 @@ class CameraController extends ValueNotifier<CameraValue> {
       enableAudio: enableAudio,
     );
 
-    CameraPlatform.instance
+    unawaited(CameraPlatform.instance
         .onCameraInitialized(_cameraId)
         .first
         .then((CameraInitializedEvent event) {
       initializeCompleter.complete(event);
-    });
+    }));
 
     await CameraPlatform.instance.initializeCamera(
       _cameraId,
@@ -444,8 +444,8 @@ class CameraController extends ValueNotifier<CameraValue> {
     if (_isDisposed) {
       return;
     }
-    _deviceOrientationSubscription?.cancel();
     _isDisposed = true;
+    await _deviceOrientationSubscription?.cancel();
     super.dispose();
     if (_initCalled != null) {
       await _initCalled;

packages/camera/camera_android/test/android_camera_test.dart

@@ -1119,7 +1119,7 @@ void main() {
         isMethodCall('startImageStream', arguments: null),
       ]);
 
-      subscription.cancel();
+      await subscription.cancel();
     });
 
     test('Should stop streaming', () async {
@@ -1136,7 +1136,7 @@ void main() {
       final StreamSubscription<CameraImageData> subscription = camera
           .onStreamedFrameAvailable(cameraId)
           .listen((CameraImageData imageData) {});
-      subscription.cancel();
+      await subscription.cancel();
 
       // Assert
       expect(channel.log, <Matcher>[

packages/camera/camera_android_camerax/analysis_options.yaml

@@ -0,0 +1,8 @@
+# TODO(stuartmorgan): Remove this file and fix all the unawaited_futures
+# violations. See https://github.com/flutter/flutter/issues/127323
+
+include: ../../../analysis_options.yaml
+
+linter:
+  rules:
+    unawaited_futures: false