[RUM] React Profiler

[MandragoreVR]

Motivation

This PR is an attempt made by Claude to have a working React Profiler. This is part of the initiative for the Agentic Week (detailed here).

Changes

Generated by Claude

Schema & type generation (rum-events-format, scripts/)

• Point rum-events-format submodule to teo.chaillou/RUM-react-profiling branch, which adds React profiling JSON
  schemas (react-profiling-browser-schema.json, react-profile-trace-schema.json, _common-schema.json)
• Register the two new schemas in scripts/lib/generatedSchemaTypes.ts so yarn json-schemas:generate produces
  packages/rum-react/src/types/reactProfiling.ts and packages/rum-react/src/types/reactProfileTrace.ts

Plugin API surface (packages/rum-core)

• Extend OnRumStartOptions in plugins.ts with profilingEndpointBuilder, configuration, lifeCycle,
  session, viewHistory, and createEncoder so plugins can access profiling infrastructure
• Pass those new fields from rumPublicApi.ts when calling callPluginsMethod('onRumStart', ...)
• Add DeflateEncoderStreamId.REACT_PROFILING = 7 in packages/core
• (unrelated, pre-existing) trackCommonViewMetrics.ts and rumPublicApi.ts contain setViewLoadingTime
  telemetry changes

React profiler core (packages/rum-react)

• createReactProfiler.ts (new, 282 lines): Windowed profiling controller that batches component renders into
  samples, rotates windows on a configurable interval or visibility change, and sends FormData payloads (event.json

• react-profiling.json) to /api/v2/profile via createFormDataTransport

• reactPlugin.ts: On onRumStart, creates and starts the profiler when the session is sampled at
  profilingSampleRate. Exposes isReactProfilingRunning() and getRunningReactProfiler() for use by the
  <ReactProfiler> component
• reactProfiler.tsx (new, 164 lines): <ReactProfiler name="..."> component using a dual strategy —
  <React.Profiler> for base_duration + sentinel LifeCycle components for per-phase durations (render,
  layoutEffect, effect)
• collectReactComponentRender.ts (new): Bridge that forwards render data from the <ReactProfiler> component
  to the running profiler's addComponentRender
• timer.ts, performance/index.ts: Timer utility for phase measurement; re-export ReactProfiler
• entries/main.ts: Export ReactProfiler and ReactProfilerContext from the package public API
• reactProfiler.spec.tsx (new, 433 lines): Unit tests for the <ReactProfiler> component

Test app (test/apps/react-shopist-like)

• Add @datadog/browser-rum and @datadog/browser-rum-react dependencies with tarball resolutions
• Initialize the RUM SDK with profilingSampleRate: 100 and the React plugin in main.tsx
• Wrap <ProductCard> with <ReactProfiler name="ProductCard">

Test helpers (packages/rum-react/test)

• Extend initializeReactPlugin to accept lifeCycle, sessionManager, viewHistory, createEncoder, and
  rumConfiguration for profiling-related tests

[datadog-datadog-prod-us1]

✨ Fix all issues with BitsAI or with Cursor

⚠️ Warnings

🧪 5 Tests failed

ReactProfiler deduplication should emit only one render per ReactProfiler per commit from Chrome Headless 146.0.0.0 (Linux 0.0.0)     (Fix with Cursor)

Error: Expected 2 to be 1.
    at <Jasmine>
    at UserContext.<anonymous> (/go/src/github.com/DataDog/browser-sdk/packages/rum-react/src/domain/performance/reactProfiler.spec.tsx:381:53 <- /tmp/_karma_webpack_186951/commons.js:414439:59)

ReactProfiler profiling build mode (React.Profiler fires) should report update phase on re-render from Chrome Headless 146.0.0.0 (Linux 0.0.0)     (Fix with Cursor)

TypeError: Cannot read properties of undefined (reading 'renders')
    at UserContext.<anonymous> (/go/src/github.com/DataDog/browser-sdk/packages/rum-react/src/domain/performance/reactProfiler.spec.tsx:198:25 <- /tmp/_karma_webpack_186951/commons.js:414327:31)

ReactProfiler sample batching should group renders from the same React commit into one sample from Chrome Headless 146.0.0.0 (Linux 0.0.0)     (Fix with Cursor)

Error: Expected 4 to be 2.
    at <Jasmine>
    at UserContext.<anonymous> (/go/src/github.com/DataDog/browser-sdk/packages/rum-react/src/domain/performance/reactProfiler.spec.tsx:334:41 <- /tmp/_karma_webpack_186951/commons.js:414409:47)

View all

ℹ️ Info

No other issues found (see more)

❄️ No new flaky tests detected

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