Programmatically set the root isolate's debug name (#6596)

An integration test will be added to the framework's repo as a followup.

Addresses flutter/flutter#22009

lib/ui/ui_dart_state.h

@@ -31,6 +31,8 @@ class UIDartState : public tonic::DartState {
 
   Dart_Port main_port() const { return main_port_; }
 
+  void set_debug_name(const std::string name) { debug_name_ = name; }
+
   const std::string& debug_name() const { return debug_name_; }
 
   const std::string& logger_prefix() const { return logger_prefix_; }

lib/ui/window.dart

@@ -714,6 +714,16 @@ class Window {
   /// semantics update cannot be used further.
   void updateSemantics(SemanticsUpdate update) native 'Window_updateSemantics';
 
+  /// Set the debug name associated with this window's root isolate.
+  ///
+  /// Normally debug names are automatically generated from the Dart port, entry
+  /// point, and source file. For example: `main.dart$main-1234`.
+  ///
+  /// This can be combined with flutter tools `--isolate-filter` flag to debug
+  /// specific root isolates. For example: `flutter attach --isolate-filter=[name]`.
+  /// Note that this does not rename any child isolates of the root.
+  void setIsolateDebugName(String name) native 'Window_setIsolateDebugName';
+
   /// Sends a message to a platform-specific plugin.
   ///
   /// The `name` parameter determines which plugin receives the message. The

lib/ui/window/window.cc

@@ -54,6 +54,17 @@ void UpdateSemantics(Dart_NativeArguments args) {
   UIDartState::Current()->window()->client()->UpdateSemantics(update);
 }
 
+void SetIsolateDebugName(Dart_NativeArguments args) {
+  Dart_Handle exception = nullptr;
+  const std::string name =
+      tonic::DartConverter<std::string>::FromArguments(args, 1, exception);
+  if (exception) {
+    Dart_ThrowException(exception);
+    return;
+  }
+  UIDartState::Current()->window()->client()->SetIsolateDebugName(name);
+}
+
 Dart_Handle SendPlatformMessage(Dart_Handle window,
                                 const std::string& name,
                                 Dart_Handle callback,
@@ -306,6 +317,7 @@ void Window::RegisterNatives(tonic::DartLibraryNatives* natives) {
       {"Window_respondToPlatformMessage", _RespondToPlatformMessage, 3, true},
       {"Window_render", Render, 2, true},
       {"Window_updateSemantics", UpdateSemantics, 2, true},
+      {"Window_setIsolateDebugName", SetIsolateDebugName, 2, true},
   });
 }
 

lib/ui/window/window.h

@@ -43,6 +43,7 @@ class WindowClient {
   virtual void Render(Scene* scene) = 0;
   virtual void UpdateSemantics(SemanticsUpdate* update) = 0;
   virtual void HandlePlatformMessage(fml::RefPtr<PlatformMessage> message) = 0;
+  virtual void SetIsolateDebugName(const std::string isolateName) = 0;
   virtual FontCollection& GetFontCollection() = 0;
 
  protected:

runtime/runtime_controller.cc

@@ -264,6 +264,14 @@ void RuntimeController::HandlePlatformMessage(
   client_.HandlePlatformMessage(std::move(message));
 }
 
+void RuntimeController::SetIsolateDebugName(const std::string name) {
+  std::shared_ptr<DartIsolate> root_isolate = root_isolate_.lock();
+  if (!root_isolate) {
+    return;
+  }
+  root_isolate->set_debug_name(name);
+}
+
 FontCollection& RuntimeController::GetFontCollection() {
   return client_.GetFontCollection();
 }

runtime/runtime_controller.h

@@ -150,6 +150,9 @@ class RuntimeController final : public WindowClient {
   // |blink::WindowClient|
   void HandlePlatformMessage(fml::RefPtr<PlatformMessage> message) override;
 
+  // |blink::WindowClient|
+  void SetIsolateDebugName(const std::string name) override;
+
   // |blink::WindowClient|
   FontCollection& GetFontCollection() override;