Adding a shutdown hook to HotRunnerConfig (#26604)

packages/flutter_tools/lib/src/run_hot.dart

@@ -36,6 +36,11 @@ class HotRunnerConfig {
   Future<bool> setupHotRestart() async {
     return true;
   }
+  /// A hook for implementations to perform any necessary operations right
+  /// before the runner is about to be shut down.
+  Future<void> runPreShutdownOperations() async {
+    return;
+  }
 }
 
 HotRunnerConfig get hotRunnerConfig => context[HotRunnerConfig];
@@ -851,6 +856,7 @@ class HotRunner extends ResidentRunner {
   @override
   Future<void> cleanupAfterSignal() async {
     await stopEchoingDeviceLog();
+    await hotRunnerConfig.runPreShutdownOperations();
     if (_didAttach) {
       appFinished();
     } else {
@@ -859,7 +865,10 @@ class HotRunner extends ResidentRunner {
   }
 
   @override
-  Future<void> preStop() => _cleanupDevFS();
+  Future<void> preStop() async {
+    await _cleanupDevFS();
+    await hotRunnerConfig.runPreShutdownOperations();
+  }
 
   @override
   Future<void> cleanupAtFinish() async {

packages/flutter_tools/test/hot_test.dart

@@ -228,6 +228,47 @@ void main() {
       Artifacts: () => mockArtifacts,
       HotRunnerConfig: () => TestHotRunnerConfig(successfulSetup: true, computeDartDependencies: false),
     });
+
+    group('shutdown hook tests', () {
+      TestHotRunnerConfig shutdownTestingConfig;
+
+      setUp(() {
+        shutdownTestingConfig = TestHotRunnerConfig(
+          successfulSetup: true,
+          computeDartDependencies: false,
+        );
+      });
+
+      testUsingContext('shutdown hook called after signal', () async {
+        final MockDevice mockDevice = MockDevice();
+        when(mockDevice.supportsHotReload).thenReturn(true);
+        when(mockDevice.supportsHotRestart).thenReturn(true);
+        when(mockDevice.supportsStopApp).thenReturn(false);
+        final List<FlutterDevice> devices = <FlutterDevice>[
+          FlutterDevice(mockDevice, generator: residentCompiler, trackWidgetCreation: false)
+        ];
+        await HotRunner(devices).cleanupAfterSignal();
+        expect(shutdownTestingConfig.shutdownHookCalled, true);
+      }, overrides: <Type, Generator> {
+        Artifacts: () => mockArtifacts,
+        HotRunnerConfig: () => shutdownTestingConfig,
+      });
+
+      testUsingContext('shutdown hook called after app stop', () async {
+        final MockDevice mockDevice = MockDevice();
+        when(mockDevice.supportsHotReload).thenReturn(true);
+        when(mockDevice.supportsHotRestart).thenReturn(true);
+        when(mockDevice.supportsStopApp).thenReturn(false);
+        final List<FlutterDevice> devices = <FlutterDevice>[
+          FlutterDevice(mockDevice, generator: residentCompiler, trackWidgetCreation: false)
+        ];
+        await HotRunner(devices).preStop();
+        expect(shutdownTestingConfig.shutdownHookCalled, true);
+      }, overrides: <Type, Generator> {
+        Artifacts: () => mockArtifacts,
+        HotRunnerConfig: () => shutdownTestingConfig,
+      });
+    });
   });
 }
 
@@ -247,9 +288,15 @@ class TestHotRunnerConfig extends HotRunnerConfig {
   }
 
   bool successfulSetup;
+  bool shutdownHookCalled = false;
 
   @override
   Future<bool> setupHotRestart() async {
     return successfulSetup;
   }
+
+  @override
+  Future<void> runPreShutdownOperations() async {
+    shutdownHookCalled = true;
+  }
 }