From 3a833d3f2f06d290286ee36ba6ef0745ad1f9fa0 Mon Sep 17 00:00:00 2001
From: Moti Zilberman <moti@meta.com>
Date: Thu, 24 Jul 2025 13:24:12 -0700
Subject: [PATCH] Move all Tracing method handling to TracingAgent (#52814)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/52814

Changelog: [Internal]

The handling of `Tracing.start` was needlessly split between `HostAgent` and `TracingAgent` because `TracingAgent` did not have a reference to the session state (which, being an Agent, it's allowed to have). This diff cleans that up.

Reviewed By: huntie

Differential Revision: D78799899

fbshipit-source-id: b05e6dae2e9b287b8708debe756b19f81d5dae06
---
 .../jsinspector-modern/HostAgent.cpp          | 22 +------------------
 .../jsinspector-modern/TracingAgent.cpp       | 14 ++++++++++++
 .../jsinspector-modern/TracingAgent.h         |  7 ++++--
 3 files changed, 20 insertions(+), 23 deletions(-)

diff --git a/packages/react-native/ReactCommon/jsinspector-modern/HostAgent.cpp b/packages/react-native/ReactCommon/jsinspector-modern/HostAgent.cpp
index a81d7b17667..b16d89395ae 100644
--- a/packages/react-native/ReactCommon/jsinspector-modern/HostAgent.cpp
+++ b/packages/react-native/ReactCommon/jsinspector-modern/HostAgent.cpp
@@ -47,7 +47,7 @@ class HostAgent::Impl final {
         hostMetadata_(std::move(hostMetadata)),
         sessionState_(sessionState),
         networkIOAgent_(NetworkIOAgent(frontendChannel, std::move(executor))),
-        tracingAgent_(TracingAgent(frontendChannel)) {}
+        tracingAgent_(TracingAgent(frontendChannel, sessionState)) {}
 
   ~Impl() {
     if (isPausedInDebuggerOverlayVisible_) {
@@ -207,26 +207,6 @@ class HostAgent::Impl final {
           .shouldSendOKResponse = true,
       };
     }
-    if (req.method == "Tracing.start") {
-      if (sessionState_.isDebuggerDomainEnabled) {
-        frontendChannel_(cdp::jsonError(
-            req.id,
-            cdp::ErrorCode::InternalError,
-            "Debugger domain is expected to be disabled before starting Tracing"));
-
-        return {
-            .isFinishedHandlingRequest = true,
-            .shouldSendOKResponse = false,
-        };
-      }
-
-      // We delegate handling of this request to TracingAgent. If not handled,
-      // then something unexpected happened - don't send an OK response.
-      return {
-          .isFinishedHandlingRequest = false,
-          .shouldSendOKResponse = false,
-      };
-    }
 
     return {
         .isFinishedHandlingRequest = false,
diff --git a/packages/react-native/ReactCommon/jsinspector-modern/TracingAgent.cpp b/packages/react-native/ReactCommon/jsinspector-modern/TracingAgent.cpp
index 0a3e365fd3d..d76e7632c77 100644
--- a/packages/react-native/ReactCommon/jsinspector-modern/TracingAgent.cpp
+++ b/packages/react-native/ReactCommon/jsinspector-modern/TracingAgent.cpp
@@ -31,9 +31,23 @@ const uint16_t PROFILE_TRACE_EVENT_CHUNK_SIZE = 1;
 
 } // namespace
 
+TracingAgent::TracingAgent(
+    FrontendChannel frontendChannel,
+    const SessionState& sessionState)
+    : frontendChannel_(std::move(frontendChannel)),
+      sessionState_(sessionState) {}
+
 bool TracingAgent::handleRequest(const cdp::PreparsedRequest& req) {
   if (req.method == "Tracing.start") {
     // @cdp Tracing.start support is experimental.
+    if (sessionState_.isDebuggerDomainEnabled) {
+      frontendChannel_(cdp::jsonError(
+          req.id,
+          cdp::ErrorCode::InternalError,
+          "Debugger domain is expected to be disabled before starting Tracing"));
+
+      return true;
+    }
     if (!instanceAgent_) {
       frontendChannel_(cdp::jsonError(
           req.id,
diff --git a/packages/react-native/ReactCommon/jsinspector-modern/TracingAgent.h b/packages/react-native/ReactCommon/jsinspector-modern/TracingAgent.h
index 95ed57efc45..f58e01f2683 100644
--- a/packages/react-native/ReactCommon/jsinspector-modern/TracingAgent.h
+++ b/packages/react-native/ReactCommon/jsinspector-modern/TracingAgent.h
@@ -25,8 +25,9 @@ class TracingAgent {
    * \param frontendChannel A channel used to send responses to the
    * frontend.
    */
-  explicit TracingAgent(FrontendChannel frontendChannel)
-      : frontendChannel_(std::move(frontendChannel)) {}
+  TracingAgent(
+      FrontendChannel frontendChannel,
+      const SessionState& sessionState);
 
   /**
    * Handle a CDP request. The response will be sent over the provided
@@ -60,6 +61,8 @@ class TracingAgent {
    * in this trace.
    */
   HighResTimeStamp instanceTracingStartTimestamp_;
+
+  const SessionState& sessionState_;
 };
 
 } // namespace facebook::react::jsinspector_modern