[flutter_tools] handle waitForExtension having no isolates (#74664)

packages/flutter_tools/lib/src/resident_runner.dart

@@ -1450,34 +1450,36 @@ abstract class ResidentRunner {
 
   // Clears the screen.
   void clearScreen() => globals.logger.clear();
+}
 
-  Future<vm_service.Isolate> waitForExtension(vm_service.VmService vmService, String extension) async {
-    final Completer<void> completer = Completer<void>();
-    try {
-      await vmService.streamListen(vm_service.EventStreams.kExtension);
-    } on Exception {
-      // do nothing
-    }
-    StreamSubscription<vm_service.Event> extensionStream;
-    extensionStream = vmService.onExtensionEvent.listen((vm_service.Event event) {
-      if (event.json['extensionKind'] == 'Flutter.FrameworkInitialization') {
-        // The 'Flutter.FrameworkInitialization' event is sent on hot restart
-        // as well, so make sure we don't try to complete this twice.
-        if (!completer.isCompleted) {
-          completer.complete();
-          extensionStream.cancel();
-        }
+@visibleForTesting
+Future<void> waitForExtension(vm_service.VmService vmService, String extension) async {
+  final Completer<void> completer = Completer<void>();
+  try {
+    await vmService.streamListen(vm_service.EventStreams.kExtension);
+  } on Exception {
+    // do nothing
+  }
+  StreamSubscription<vm_service.Event> extensionStream;
+  extensionStream = vmService.onExtensionEvent.listen((vm_service.Event event) {
+    if (event.json['extensionKind'] == 'Flutter.FrameworkInitialization') {
+      // The 'Flutter.FrameworkInitialization' event is sent on hot restart
+      // as well, so make sure we don't try to complete this twice.
+      if (!completer.isCompleted) {
+        completer.complete();
+        extensionStream.cancel();
       }
-    });
-    final vm_service.IsolateRef isolateRef = (await vmService.getVM()).isolates.first;
+    }
+  });
+  final vm_service.VM vm = await vmService.getVM();
+  if (vm.isolates.isNotEmpty) {
+    final vm_service.IsolateRef isolateRef = vm.isolates.first;
     final vm_service.Isolate isolate = await vmService.getIsolate(isolateRef.id);
     if (isolate.extensionRPCs.contains(extension)) {
-      return isolate;
+      return;
     }
-    await completer.future;
-    return isolate;
   }
-
+  await completer.future;
 }
 
 class OperationResult {

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

@@ -3001,6 +3001,86 @@ void main() {
     expect(nextPlatform('fuchsia', TestFeatureFlags(isMacOSEnabled: true)), 'macOS');
     expect(() => nextPlatform('unknown', TestFeatureFlags()), throwsAssertionError);
   });
+
+  testWithoutContext('wait for extension handles an immediate extension', () {
+    final vm_service.Isolate isolate = vm_service.Isolate(
+      id: '1',
+      pauseEvent: vm_service.Event(
+        kind: vm_service.EventKind.kResume,
+        timestamp: 0
+      ),
+      breakpoints: <vm_service.Breakpoint>[],
+      exceptionPauseMode: null,
+      libraries: <vm_service.LibraryRef>[
+        vm_service.LibraryRef(
+          id: '1',
+          uri: 'file:///hello_world/main.dart',
+          name: '',
+        ),
+      ],
+      livePorts: 0,
+      name: 'test',
+      number: '1',
+      pauseOnExit: false,
+      runnable: true,
+      startTime: 0,
+      isSystemIsolate: false,
+      isolateFlags: <vm_service.IsolateFlag>[],
+      extensionRPCs: <String>['foo']
+    );
+
+    final FakeVmServiceHost fakeVmServiceHost = FakeVmServiceHost(requests: <VmServiceExpectation>[
+      const FakeVmServiceRequest(
+        method: 'streamListen',
+        args: <String, Object>{
+          'streamId': 'Extension',
+        }
+      ),
+      FakeVmServiceRequest(method: 'getVM', jsonResponse: fakeVM.toJson()),
+      FakeVmServiceRequest(
+        method: 'getIsolate',
+        jsonResponse: isolate.toJson(),
+        args: <String, Object>{
+          'isolateId': '1',
+        },
+      ),
+    ]);
+    waitForExtension(fakeVmServiceHost.vmService, 'foo');
+  });
+
+  testWithoutContext('wait for extension handles no isolates', () {
+    final FakeVmServiceHost fakeVmServiceHost = FakeVmServiceHost(requests: <VmServiceExpectation>[
+      const FakeVmServiceRequest(
+        method: 'streamListen',
+        args: <String, Object>{
+          'streamId': 'Extension',
+        }
+      ),
+      FakeVmServiceRequest(method: 'getVM', jsonResponse: vm_service.VM(
+        isolates: <vm_service.IsolateRef>[],
+        pid: 1,
+        hostCPU: '',
+        isolateGroups: <vm_service.IsolateGroupRef>[],
+        targetCPU: '',
+        startTime: 0,
+        name: 'dart',
+        architectureBits: 64,
+        operatingSystem: '',
+        version: '',
+        systemIsolateGroups: <vm_service.IsolateGroupRef>[],
+        systemIsolates: <vm_service.IsolateRef>[],
+      ).toJson()),
+      FakeVmServiceStreamResponse(
+        streamId: 'Extension',
+        event: vm_service.Event(
+          timestamp: 0,
+          extensionKind: 'Flutter.FrameworkInitialization',
+          kind: 'test',
+        ),
+      ),
+    ]);
+    waitForExtension(fakeVmServiceHost.vmService, 'foo');
+  });
 }
 
 class MockFlutterDevice extends Mock implements FlutterDevice {}