Reland "Fix issue where DevTools would not be immediately available when using --start-paused (#126698)"

packages/flutter_tools/lib/src/resident_devtools_handler.dart

@@ -35,6 +35,7 @@ abstract class ResidentDevtoolsHandler {
   Future<void> serveAndAnnounceDevTools({
     Uri? devToolsServerAddress,
     required List<FlutterDevice?> flutterDevices,
+    bool isStartPaused = false,
   });
 
   bool launchDevToolsInBrowser({required List<FlutterDevice?> flutterDevices});
@@ -71,6 +72,7 @@ class FlutterResidentDevtoolsHandler implements ResidentDevtoolsHandler {
   Future<void> serveAndAnnounceDevTools({
     Uri? devToolsServerAddress,
     required List<FlutterDevice?> flutterDevices,
+    bool isStartPaused = false,
   }) async {
     assert(!_readyToAnnounce);
     if (!_residentRunner.supportsServiceProtocol || _devToolsLauncher == null) {
@@ -88,20 +90,10 @@ class FlutterResidentDevtoolsHandler implements ResidentDevtoolsHandler {
       assert(!_readyToAnnounce);
       return;
     }
-    final List<FlutterDevice?> devicesWithExtension = await _devicesWithExtensions(flutterDevices);
-    await _maybeCallDevToolsUriServiceExtension(devicesWithExtension);
-    await _callConnectedVmServiceUriExtension(devicesWithExtension);
-
-    if (_shutdown) {
-      // If we're shutting down, no point reporting the debugger list.
-      return;
-    }
-    _readyToAnnounce = true;
-    assert(_devToolsLauncher!.activeDevToolsServer != null);
 
     final Uri? devToolsUrl = _devToolsLauncher!.devToolsUrl;
     if (devToolsUrl != null) {
-      for (final FlutterDevice? device in devicesWithExtension) {
+      for (final FlutterDevice? device in flutterDevices) {
         if (device == null) {
           continue;
         }
@@ -111,11 +103,43 @@ class FlutterResidentDevtoolsHandler implements ResidentDevtoolsHandler {
       }
     }
 
+    Future<void> callServiceExtensions() async {
+      final List<FlutterDevice?> devicesWithExtension = await _devicesWithExtensions(flutterDevices);
+      await Future.wait(
+        <Future<void>>[
+          _maybeCallDevToolsUriServiceExtension(devicesWithExtension),
+          _callConnectedVmServiceUriExtension(devicesWithExtension)
+        ]
+      );
+    }
+
+    // If the application is starting paused, we can't invoke service extensions
+    // as they're handled on the target app's paused isolate. Since invoking
+    // service extensions will block in this situation, we should wait to invoke
+    // them until after we've output the DevTools connection details.
+    if (!isStartPaused) {
+      await callServiceExtensions();
+    }
+
+    // This check needs to happen after the possible asynchronous call above,
+    // otherwise a shutdown event might be missed and the DevTools launcher may
+    // no longer be initialized.
+    if (_shutdown) {
+      // If we're shutting down, no point reporting the debugger list.
+      return;
+    }
+
+    _readyToAnnounce = true;
+    assert(_devToolsLauncher!.activeDevToolsServer != null);
     if (_residentRunner.reportedDebuggers) {
       // Since the DevTools only just became available, we haven't had a chance to
       // report their URLs yet. Do so now.
       _residentRunner.printDebuggerList(includeVmService: false);
     }
+
+    if (isStartPaused) {
+      await callServiceExtensions();
+    }
   }
 
   // This must be guaranteed not to return a Future that fails.
@@ -295,7 +319,11 @@ class NoOpDevtoolsHandler implements ResidentDevtoolsHandler {
   }
 
   @override
-  Future<void> serveAndAnnounceDevTools({Uri? devToolsServerAddress, List<FlutterDevice?>? flutterDevices}) async {
+  Future<void> serveAndAnnounceDevTools({
+    Uri? devToolsServerAddress,
+    List<FlutterDevice?>? flutterDevices,
+    bool isStartPaused = false,
+  }) async {
     return;
   }
 

packages/flutter_tools/lib/src/run_cold.dart

@@ -86,6 +86,7 @@ class ColdRunner extends ResidentRunner {
         unawaited(residentDevtoolsHandler!.serveAndAnnounceDevTools(
           devToolsServerAddress: debuggingOptions.devToolsServerAddress,
           flutterDevices: flutterDevices,
+          isStartPaused: debuggingOptions.startPaused,
         ));
       }
       if (debuggingOptions.serveObservatory) {
@@ -173,6 +174,7 @@ class ColdRunner extends ResidentRunner {
         unawaited(residentDevtoolsHandler!.serveAndAnnounceDevTools(
           devToolsServerAddress: debuggingOptions.devToolsServerAddress,
           flutterDevices: flutterDevices,
+          isStartPaused: debuggingOptions.startPaused,
         ));
       }
       if (debuggingOptions.serveObservatory) {

packages/flutter_tools/lib/src/run_hot.dart

@@ -249,6 +249,7 @@ class HotRunner extends ResidentRunner {
       unawaited(residentDevtoolsHandler!.serveAndAnnounceDevTools(
         devToolsServerAddress: debuggingOptions.devToolsServerAddress,
         flutterDevices: flutterDevices,
+        isStartPaused: debuggingOptions.startPaused,
       ));
     }
 

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

@@ -156,14 +156,14 @@ void main() {
         },
       ),
       listViews,
+      listViews,
       const FakeVmServiceRequest(
         method: 'ext.flutter.activeDevToolsServerAddress',
         args: <String, Object>{
           'isolateId': '1',
           'value': 'http://localhost:8080',
         },
       ),
-      listViews,
       const FakeVmServiceRequest(
         method: 'ext.flutter.connectedVmServiceUri',
         args: <String, Object>{
@@ -314,14 +314,14 @@ void main() {
         },
       ),
       listViews,
+      listViews,
       const FakeVmServiceRequest(
         method: 'ext.flutter.activeDevToolsServerAddress',
         args: <String, Object>{
           'isolateId': '1',
           'value': 'http://localhost:8080',
         },
       ),
-      listViews,
       const FakeVmServiceRequest(
         method: 'ext.flutter.connectedVmServiceUri',
         args: <String, Object>{

packages/flutter_tools/test/integration.shard/devtools_uri_test.dart

@@ -0,0 +1,53 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// 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_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/base/io.dart';
+import 'package:flutter_tools/src/convert.dart';
+
+import '../src/common.dart';
+import 'test_data/basic_project.dart';
+import 'test_utils.dart';
+
+void main() {
+  late Directory tempDir;
+  final BasicProject project = BasicProject();
+
+  setUp(() async {
+    tempDir = createResolvedTempDirectorySync('run_test.');
+    await project.setUpIn(tempDir);
+  });
+
+  tearDown(() async {
+    tryToDelete(tempDir);
+  });
+
+  // Regression test for https://github.com/flutter/flutter/issues/126691
+  testWithoutContext('flutter run --start-paused prints DevTools URI', () async {
+    final Completer<void> completer = Completer<void>();
+    final RegExp matcher = RegExp(r'The Flutter DevTools debugger and profiler on');
+
+    final String flutterBin = fileSystem.path.join(getFlutterRoot(), 'bin', 'flutter');
+    final Process process = await processManager.start(<String>[
+      flutterBin,
+      'run',
+      '--start-paused',
+      '-d',
+      'flutter-tester',
+    ], workingDirectory: tempDir.path);
+
+    late final StreamSubscription<String> sub;
+    sub = process.stdout.transform(utf8.decoder).listen((String message) {
+      if (message.contains(matcher)) {
+        completer.complete();
+        sub.cancel();
+      }
+    });
+    await completer.future;
+    process.kill();
+    await process.exitCode;
+  });
+}