Define HostTargetTracingDelegate

packages/react-native/ReactCommon/jsinspector-modern/HostTarget.h

@@ -55,6 +55,36 @@ struct HostTargetMetadata {
   std::optional<std::string> reactNativeVersion{};
 };
 
+/**
+ * Receives any performance-related events from a HostTarget: could be Tracing, Performance Monitor, etc.
+ */
+class HostTargetTracingDelegate {
+ public:
+  HostTargetTracingDelegate() = default;
+  virtual ~HostTargetTracingDelegate() = default;
+
+  /**
+   * Fired when the corresponding HostTarget started recording a tracing session.
+   * The tracing state is expected to be initialized at this point and the delegate should be able to record events
+   * through HostTarget.
+   */
+  virtual void onTracingStarted(tracing::Mode /* tracingMode */, bool /* screenshotsCategoryEnabled */) {}
+
+  /**
+   * Fired when the corresponding HostTarget is about to end recording a tracing session.
+   * The tracing state is expected to be still initialized during the call and the delegate should be able to record
+   * events through HostTarget.
+   *
+   * Any attempts to record events after this callback is finished will fail.
+   */
+  virtual void onTracingStopped() {}
+
+  HostTargetTracingDelegate(const HostTargetTracingDelegate &) = delete;
+  HostTargetTracingDelegate(HostTargetTracingDelegate &&) = delete;
+  HostTargetTracingDelegate &operator=(const HostTargetTracingDelegate &) = delete;
+  HostTargetTracingDelegate &operator=(HostTargetTracingDelegate &&) = delete;
+};
+
 /**
  * Receives events from a HostTarget. This is a shared interface that each
  * React Native platform needs to implement in order to integrate with the
@@ -161,6 +191,14 @@ class HostTargetDelegate : public LoadNetworkResourceDelegate {
   {
     return std::nullopt;
   }
+
+  /**
+   * An optional delegate that will be used by HostTarget to notify about tracing-related events.
+   */
+  virtual HostTargetTracingDelegate *getTracingDelegate()
+  {
+    return nullptr;
+  }
 };
 
 /**
@@ -230,12 +268,15 @@ class JSINSPECTOR_EXPORT HostTarget : public EnableExecutorFromThis<HostTarget>
  public:
   /**
    * Constructs a new HostTarget.
+   *
    * \param delegate The HostTargetDelegate that will
    * receive events from this HostTarget. The caller is responsible for ensuring
    * that the HostTargetDelegate outlives this object.
+   *
    * \param executor An executor that may be used to call methods on this
    * HostTarget while it exists. \c create additionally guarantees that the
    * executor will not be called after the HostTarget is destroyed.
+   *
    * \note Copies of the provided executor may be destroyed on arbitrary
    * threads, including after the HostTarget is destroyed. Callers must ensure
    * that such destructor calls are safe - e.g. if using a lambda as the
@@ -326,15 +367,11 @@ class JSINSPECTOR_EXPORT HostTarget : public EnableExecutorFromThis<HostTarget>
    */
   void emitTraceRecordingForFirstFuseboxClient(tracing::TraceRecordingState traceRecording) const;
 
-  /**
-   * Emits a system state changed event to all active sessions.
-   */
-  void emitSystemStateChanged(bool isSingleHost) const;
-
  private:
   /**
    * Constructs a new HostTarget.
    * The caller must call setExecutor immediately afterwards.
+   *
    * \param delegate The HostTargetDelegate that will
    * receive events from this HostTarget. The caller is responsible for ensuring
    * that the HostTargetDelegate outlives this object.

packages/react-native/ReactCommon/jsinspector-modern/HostTargetTracing.cpp

@@ -35,23 +35,34 @@ bool HostTarget::startTracing(
   if (traceRecording_ != nullptr) {
     if (traceRecording_->isBackgroundInitiated() &&
         tracingMode == tracing::Mode::CDP) {
-      traceRecording_.reset();
+      stopTracing();
     } else {
       return false;
     }
   }
 
+  auto screenshotsCategoryEnabled =
+      enabledCategories.contains(tracing::Category::Screenshot);
+
   traceRecording_ = std::make_unique<HostTargetTraceRecording>(
       *this, tracingMode, std::move(enabledCategories));
   traceRecording_->setTracedInstance(currentInstance_.get());
   traceRecording_->start();
 
+  if (auto tracingDelegate = delegate_.getTracingDelegate()) {
+    tracingDelegate->onTracingStarted(tracingMode, screenshotsCategoryEnabled);
+  }
+
   return true;
 }
 
 tracing::TraceRecordingState HostTarget::stopTracing() {
   assert(traceRecording_ != nullptr && "No tracing in progress");
 
+  if (auto tracingDelegate = delegate_.getTracingDelegate()) {
+    tracingDelegate->onTracingStopped();
+  }
+
   auto state = traceRecording_->stop();
   traceRecording_.reset();
 

packages/react-native/ReactCommon/jsinspector-modern/tests/HostTargetTest.cpp

@@ -1526,4 +1526,57 @@ TEST_F(HostTargetTest, IOReadSizeValidation) {
       })");
 }
 
+TEST_F(HostTargetTest, TracingDelegateIsNotifiedOnCDPRequest) {
+  connect();
+  InSequence s;
+
+  EXPECT_CALL(
+      hostTargetDelegate_.getTracingDelegateMock(),
+      onTracingStarted(Eq(tracing::Mode::CDP), Eq(false)))
+      .Times(1)
+      .RetiresOnSaturation();
+  EXPECT_CALL(fromPage(), onMessage(JsonEq(R"({
+                                               "id": 1,
+                                               "result": {}
+                                             })")));
+  toPage_->sendMessage(R"({
+                        "id": 1,
+                        "method": "Tracing.start"
+                      })");
+
+  EXPECT_CALL(hostTargetDelegate_.getTracingDelegateMock(), onTracingStopped())
+      .Times(1)
+      .RetiresOnSaturation();
+  EXPECT_CALL(fromPage(), onMessage(JsonEq(R"({
+                                               "id": 1,
+                                               "result": {}
+                                             })")));
+  EXPECT_CALL(
+      fromPage(),
+      onMessage(JsonParsed(
+          testing::AllOf(
+              AtJsonPtr("/method", "Tracing.tracingComplete"),
+              AtJsonPtr("/params/dataLossOccurred", false)))));
+  toPage_->sendMessage(R"({
+                        "id": 1,
+                        "method": "Tracing.end"
+                      })");
+}
+
+TEST_F(HostTargetTest, TracingDelegateIsNotifiedOnDirectTracingCall) {
+  connect();
+
+  EXPECT_CALL(
+      hostTargetDelegate_.getTracingDelegateMock(),
+      onTracingStarted(Eq(tracing::Mode::Background), Eq(false)))
+      .Times(1)
+      .RetiresOnSaturation();
+  page_->startTracing(tracing::Mode::Background, {});
+
+  EXPECT_CALL(hostTargetDelegate_.getTracingDelegateMock(), onTracingStopped())
+      .Times(1)
+      .RetiresOnSaturation();
+  page_->stopTracing();
+}
+
 } // namespace facebook::react::jsinspector_modern

packages/react-native/ReactCommon/jsinspector-modern/tests/InspectorMocks.h

@@ -113,6 +113,12 @@ class MockInspectorPackagerConnectionDelegate : public InspectorPackagerConnecti
   folly::Executor &executor_;
 };
 
+class MockHostTargetTracingDelegate : public HostTargetTracingDelegate {
+ public:
+  MOCK_METHOD(void, onTracingStarted, (tracing::Mode tracingMode, bool screenshotsCategoryEnabled), (override));
+  MOCK_METHOD(void, onTracingStopped, (), (override));
+};
+
 class MockHostTargetDelegate : public HostTargetDelegate {
  public:
   // HostTargetDelegate methods
@@ -131,6 +137,20 @@ class MockHostTargetDelegate : public HostTargetDelegate {
       loadNetworkResource,
       (const LoadNetworkResourceRequest &params, ScopedExecutor<NetworkRequestListener> executor),
       (override));
+
+  HostTargetTracingDelegate *getTracingDelegate() override
+  {
+    return mockTracingDelegate_.get();
+  }
+
+  MockHostTargetTracingDelegate &getTracingDelegateMock()
+  {
+    return *mockTracingDelegate_;
+  }
+
+ private:
+  std::unique_ptr<MockHostTargetTracingDelegate> mockTracingDelegate_ =
+      std::make_unique<MockHostTargetTracingDelegate>();
 };
 
 class MockInstanceTargetDelegate : public InstanceTargetDelegate {};