Extract TraceEvent serialization logic (#52869)

Summary:
Pull Request resolved: #52869

# Changelog: [Internal]

We are exctracting a logic for serialization of TraceEvent into a dedicated serializer class.

Conceptually:
- PerformanceTracer would be a local TraceEvent engine that is responsible for constructing and buffering TraceEvents.
- TraceEventSerializer will have a single responsibility: transforming from local structs to serialized json objects that are ready to be dispatched over CDP Tracing domain.

This would help avoid scenarios, where we are passing around `folly:dynamic` between internal subsystems: serialization should only happen right before emtting a CDP message.

Reviewed By: huntie

Differential Revision: D78738370

fbshipit-source-id: a8e33e857192a02dc048d504abe072679ef8ce82

Author: hoxyq

packages/react-native/ReactCommon/jsinspector-modern/tracing/PerformanceTracer.cpp

@@ -7,13 +7,13 @@
 
 #include "PerformanceTracer.h"
 #include "Timing.h"
+#include "TraceEventSerializer.h"
 
 #include <oscompat/OSCompat.h>
 #include <react/timing/primitives.h>
 
 #include <folly/json.h>
 
-#include <array>
 #include <mutex>
 
 namespace facebook::react::jsinspector_modern::tracing {
@@ -98,7 +98,8 @@ void PerformanceTracer::collectEvents(
   auto serializedTraceEvents = folly::dynamic::array();
   for (auto&& event : localBuffer) {
     // Emit trace events
-    serializedTraceEvents.push_back(serializeTraceEvent(std::move(event)));
+    serializedTraceEvents.push_back(
+        TraceEventSerializer::serialize(std::move(event)));
 
     if (serializedTraceEvents.size() == chunkSize) {
       resultCallback(std::move(serializedTraceEvents));
@@ -125,7 +126,7 @@ folly::dynamic PerformanceTracer::collectEvents(uint16_t chunkSize) {
   auto chunk = folly::dynamic::array();
   chunk.reserve(chunkSize);
   for (auto&& event : localBuffer) {
-    chunk.push_back(serializeTraceEvent(std::move(event)));
+    chunk.push_back(TraceEventSerializer::serialize(std::move(event)));
 
     if (chunk.size() == chunkSize) {
       chunks.push_back(std::move(chunk));
@@ -380,7 +381,7 @@ folly::dynamic PerformanceTracer::getSerializedRuntimeProfileTraceEvent(
     HighResTimeStamp profileTimestamp) {
   // CDT prioritizes event timestamp over startTime metadata field.
   // https://fburl.com/lo764pf4
-  return serializeTraceEvent(TraceEvent{
+  return TraceEventSerializer::serialize(TraceEvent{
       .id = profileId,
       .name = "Profile",
       .cat = "disabled-by-default-v8.cpu_profiler",
@@ -401,7 +402,7 @@ folly::dynamic PerformanceTracer::getSerializedRuntimeProfileChunkTraceEvent(
     uint64_t threadId,
     HighResTimeStamp chunkTimestamp,
     const tracing::TraceEventProfileChunk& traceEventProfileChunk) {
-  return serializeTraceEvent(TraceEvent{
+  return TraceEventSerializer::serialize(TraceEvent{
       .id = profileId,
       .name = "ProfileChunk",
       .cat = "disabled-by-default-v8.cpu_profiler",
@@ -414,27 +415,4 @@ folly::dynamic PerformanceTracer::getSerializedRuntimeProfileChunkTraceEvent(
   });
 }
 
-folly::dynamic PerformanceTracer::serializeTraceEvent(
-    TraceEvent&& event) const {
-  folly::dynamic result = folly::dynamic::object;
-
-  if (event.id.has_value()) {
-    std::array<char, 16> buffer{};
-    snprintf(buffer.data(), buffer.size(), "0x%x", event.id.value());
-    result["id"] = buffer.data();
-  }
-  result["name"] = std::move(event.name);
-  result["cat"] = std::move(event.cat);
-  result["ph"] = std::string(1, event.ph);
-  result["ts"] = highResTimeStampToTracingClockTimeStamp(event.ts);
-  result["pid"] = event.pid;
-  result["tid"] = event.tid;
-  result["args"] = std::move(event.args);
-  if (event.dur.has_value()) {
-    result["dur"] = highResDurationToTracingClockDuration(event.dur.value());
-  }
-
-  return result;
-}
-
 } // namespace facebook::react::jsinspector_modern::tracing

packages/react-native/ReactCommon/jsinspector-modern/tracing/PerformanceTracer.h

@@ -156,14 +156,6 @@ class PerformanceTracer {
   PerformanceTracer& operator=(const PerformanceTracer&) = delete;
   ~PerformanceTracer() = default;
 
-  /**
-   * Serialize a TraceEvent into a folly::dynamic object.
-   * \param event rvalue reference to the TraceEvent object.
-   * \return folly::dynamic object that represents a serialized into JSON Trace
-   * Event for CDP.
-   */
-  folly::dynamic serializeTraceEvent(TraceEvent&& event) const;
-
   const uint64_t processId_;
 
   /**

packages/react-native/ReactCommon/jsinspector-modern/tracing/TraceEventSerializer.cpp

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "TraceEventSerializer.h"
+#include "Timing.h"
+
+namespace facebook::react::jsinspector_modern::tracing {
+
+/* static */ folly::dynamic TraceEventSerializer::serialize(
+    TraceEvent&& event) {
+  folly::dynamic result = folly::dynamic::object;
+
+  if (event.id.has_value()) {
+    std::array<char, 16> buffer{};
+    snprintf(buffer.data(), buffer.size(), "0x%x", event.id.value());
+    result["id"] = buffer.data();
+  }
+  result["name"] = std::move(event.name);
+  result["cat"] = std::move(event.cat);
+  result["ph"] = std::string(1, event.ph);
+  result["ts"] = highResTimeStampToTracingClockTimeStamp(event.ts);
+  result["pid"] = event.pid;
+  result["tid"] = event.tid;
+  result["args"] = std::move(event.args);
+  if (event.dur.has_value()) {
+    result["dur"] = highResDurationToTracingClockDuration(event.dur.value());
+  }
+
+  return result;
+}
+
+} // namespace facebook::react::jsinspector_modern::tracing

packages/react-native/ReactCommon/jsinspector-modern/tracing/TraceEventSerializer.h

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include "TraceEvent.h"
+
+#include <folly/dynamic.h>
+
+namespace facebook::react::jsinspector_modern::tracing {
+
+/**
+ * This class is only responsible for serializing a local TraceEvent
+ * representation into JSON, that should be ready to be dispatched over the
+ * protocol.
+ */
+class TraceEventSerializer {
+ public:
+  /**
+   * Serializes a TraceEvent to a folly::dynamic object.
+   *
+   * \param event rvalue reference to the TraceEvent object.
+   * \return A folly::dynamic object that represents a serialized into JSON
+   * Trace Event for CDP.
+   */
+  static folly::dynamic serialize(TraceEvent&& event);
+};
+
+} // namespace facebook::react::jsinspector_modern::tracing