Prepare IsolateManager to become source of truth for isPaused for an isolate.

CONTRIBUTING.md

@@ -8,11 +8,13 @@ This page instructs how to contribute code changes to DevTools.
 > If you just want to test newest functionality, follow
 [beta testing guidance](https://github.com/flutter/devtools/blob/master/BETA_TESTING.md).
 
-To contribute code you must complete the
+Before contributing code:
+
+1. Complete the
 [Contributor License Agreement](https://cla.developers.google.com/clas).
-You can do this online, and it only takes a minute. If you've never submitted code before,
-you must add your (or your organization's) name and contact info to the [AUTHORS](AUTHORS)
-file.
+You can do this online, and it only takes a minute.
+
+2. Understand [coding agreements](packages/README.md).
 
 ## Workflow for making changes
 

packages/README.md

@@ -1,5 +1,9 @@
 # Coding agreements in DevTools
 
+We fully follow [Effective Dart](https://dart.dev/guides/language/effective-dart)
+and some items of
+[Style guide for Flutter repo](https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo):
+
 ## Order of getters and setters
 
 When an object owns and exposes a (listenable) value,
@@ -10,3 +14,7 @@ in compliance with [Flutter repo style guide]( https://github.com/flutter/flutte
 1. Public getter
 2. Private field
 3. Public setter (when needed)
+
+## Naming for typedefs and function variables
+
+Follow [Flutter repo naming rules for typedefs and function variables](https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#naming-rules-for-typedefs-and-function-variables).

packages/devtools_app/lib/src/service/isolate_manager.dart

@@ -123,7 +123,7 @@ class IsolateManager extends Disposer {
     final state = _isolateStates[isolateRef];
     if (state != null) {
       // Isolate might have already been closed.
-      state.onIsolateLoaded(isolate);
+      state.handleIsolateLoad(isolate);
     }
   }
 
@@ -249,14 +249,15 @@ class IsolateManager extends Disposer {
       service.onDebugEvent.listen(_handleDebugEvent),
     );
 
-    // We don't yet known the main isolate.
+    // We don't know the main isolate yet.
     _mainIsolate.value = null;
   }
 
-  Future<Isolate?> getIsolateCached(IsolateRef isolateRef) {
-    final isolateState =
-        _isolateStates.putIfAbsent(isolateRef, () => IsolateState(isolateRef));
-    return isolateState.isolate;
+  IsolateState isolateState(IsolateRef isolateRef) {
+    return _isolateStates.putIfAbsent(
+      isolateRef,
+      () => IsolateState(isolateRef),
+    );
   }
 
   void _handleDebugEvent(Event event) {

packages/devtools_app/lib/src/service/isolate_state.dart

@@ -11,23 +11,22 @@ import 'package:vm_service/vm_service.dart' hide Error;
 class IsolateState {
   IsolateState(this.isolateRef);
 
-  ValueListenable<bool?> get isPaused => _isPaused;
-
   final IsolateRef isolateRef;
 
+  /// Returns null if only this instance of [IsolateState] is disposed.
   Future<Isolate?> get isolate => _completer.future;
   Completer<Isolate?> _completer = Completer();
 
   Isolate? get isolateNow => _isolateNow;
   Isolate? _isolateNow;
 
-  /// Paused is null until we know whether the isolate is paused or not.
-  final _isPaused = ValueNotifier<bool?>(null);
+  ValueListenable<bool> get isPaused => _isPaused;
+  final _isPaused = ValueNotifier<bool>(false);
 
-  void onIsolateLoaded(Isolate isolate) {
+  void handleIsolateLoad(Isolate isolate) {
     _isolateNow = isolate;
     _completer.complete(isolate);
-    _isPaused.value ??= isolate.pauseEvent != null &&
+    _isPaused.value = isolate.pauseEvent != null &&
         isolate.pauseEvent!.kind != EventKind.kResume;
   }
 

packages/devtools_app/lib/src/service/service_extension_manager.dart

@@ -165,7 +165,8 @@ class ServiceExtensionManager extends Disposer {
     _checkForFirstFrameStarted = false;
 
     final isolateRef = _isolateManager.mainIsolate.value!;
-    final Isolate? isolate = await _isolateManager.getIsolateCached(isolateRef);
+    final Isolate? isolate =
+        await _isolateManager.isolateState(isolateRef).isolate;
 
     if (isolate == null) return;
 
@@ -316,7 +317,8 @@ class ServiceExtensionManager extends Disposer {
 
     if (isolateRef != _mainIsolate) return;
 
-    final Isolate? isolate = await _isolateManager.getIsolateCached(isolateRef);
+    final Isolate? isolate =
+        await _isolateManager.isolateState(isolateRef).isolate;
     if (isolateRef != _mainIsolate) return;
 
     // Do not try to restore Dart IO extensions for a paused isolate.
@@ -400,7 +402,7 @@ class ServiceExtensionManager extends Disposer {
 
     if (mainIsolate == null) return;
     final Isolate? isolate =
-        await _isolateManager.getIsolateCached(mainIsolate);
+        await _isolateManager.isolateState(mainIsolate).isolate;
     if (_isolateManager.mainIsolate.value != mainIsolate) return;
 
     // Do not try to call Dart IO extensions for a paused isolate.
@@ -546,7 +548,7 @@ class ServiceExtensionManager extends Disposer {
     if (mainIsolateRef != null) {
       _checkForFirstFrameStarted = false;
       final mainIsolate =
-          await _isolateManager.getIsolateCached(mainIsolateRef);
+          await _isolateManager.isolateState(mainIsolateRef).isolate;
       if (mainIsolate != null)
         await _registerMainIsolate(mainIsolate, mainIsolateRef);
     }

packages/devtools_app/lib/src/shared/console/widgets/evaluate.dart

@@ -301,7 +301,7 @@ class ExpressionEvalFieldState extends State<ExpressionEvalField>
 
     // Only try to eval if we are paused.
     if (!serviceManager
-        .isolateManager.mainIsolateDebuggerState!.isPaused.value!) {
+        .isolateManager.mainIsolateDebuggerState!.isPaused.value) {
       notificationService
           .push('Application must be paused to support expression evaluation.');
       return;

packages/devtools_app/lib/src/shared/eval_on_dart_library.dart

@@ -109,7 +109,7 @@ class EvalOnDartLibrary extends DisposableController
 
     try {
       final Isolate? isolate =
-          await serviceManager.isolateManager.getIsolateCached(isolateRef);
+          await serviceManager.isolateManager.isolateState(isolateRef).isolate;
       if (_currentRequestId != requestId) {
         // The initialize request is obsolete.
         return;

packages/devtools_test/lib/src/mocks/mocks.dart

@@ -134,7 +134,7 @@ class FakeVM extends Fake implements VM {
 
 class MockIsolateState extends Mock implements IsolateState {
   @override
-  ValueListenable<bool?> get isPaused => ValueNotifier<bool>(false);
+  ValueListenable<bool> get isPaused => ValueNotifier<bool>(false);
 }
 
 class MockIsolate extends Mock implements Isolate {}