[DevTools] Remove experimental __IS_INTERNAL_MCP_BUILD__ flag and related code

[everettbu]

Mirror of facebook/react#35755
Original author: hoxyq

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This is unused.

[greptile-apps]

Greptile Overview

Greptile Summary

This PR removes the experimental __IS_INTERNAL_MCP_BUILD__ build flag across DevTools configs (ESLint/Flow globals, Jest env setup, and various webpack DefinePlugin constants), and deletes the MCP-only renderer interface method that was conditionally exposed behind that flag.

Most changes are straightforward cleanup, but removing the renderer interface method appears to break the MCP server tool under compiler/packages/react-mcp-server, which still expects __internal_only_getComponentTree to exist on the renderer interface.

Confidence Score: 2/5

• Not safe to merge as-is due to a confirmed runtime break in the MCP server tool.
• The flag removal itself is consistent, but the PR also removes __internal_only_getComponentTree from the DevTools renderer interface while compiler/packages/react-mcp-server/src/tools/componentTree.ts still calls it, which will now throw at runtime.
• packages/react-devtools-shared/src/backend/fiber/renderer.js (and compiler/packages/react-mcp-server/src/tools/componentTree.ts caller)

Important Files Changed

Filename	Overview
.eslintrc.js	Removes IS_INTERNAL_MCP_BUILD from declared ESLint globals.
packages/react-devtools-core/webpack.backend.js	Removes IS_INTERNAL_MCP_BUILD from DefinePlugin globals for backend build.
packages/react-devtools-core/webpack.standalone.js	Removes IS_INTERNAL_MCP_BUILD from DefinePlugin globals for standalone build.
packages/react-devtools-extensions/webpack.config.js	Removes IS_INTERNAL_MCP_BUILD env handling and related stats filename suffix and DefinePlugin global.
packages/react-devtools-fusebox/webpack.config.frontend.js	Removes IS_INTERNAL_MCP_BUILD from DefinePlugin globals for fusebox frontend.
packages/react-devtools-inline/webpack.config.js	Removes IS_INTERNAL_MCP_BUILD from DefinePlugin globals for inline build.
packages/react-devtools-shared/src/backend/fiber/renderer.js	Removes internal MCP-only __internal_only_getComponentTree export; this appears to break compiler/packages/react-mcp-server which calls it.
scripts/flow/react-devtools.js	Removes Flow global declaration for IS_INTERNAL_MCP_BUILD.
scripts/jest/devtools/setupEnv.js	Removes Jest test global IS_INTERNAL_MCP_BUILD initialization.

[greptile-apps]

_{9 files reviewed, 1 comment}

_{Edit Code Review Agent Settings | Greptile}

[greptile-apps]

Breaks MCP component tree tool

This PR removes the __internal_only_getComponentTree function from the renderer interface (it used to be conditionally injected behind __IS_INTERNAL_MCP_BUILD__). However compiler/packages/react-mcp-server/src/tools/componentTree.ts still calls .get(1).__internal_only_getComponentTree(), so this will now throw at runtime (method is undefined). Either update/remove the MCP server tool, or keep exposing a supported API for extracting the component tree.

Prompt To Fix With AI

This is a comment left during a code review.
Path: packages/react-devtools-shared/src/backend/fiber/renderer.js
Line: 8817:8819

Comment:
**Breaks MCP component tree tool**

This PR removes the `__internal_only_getComponentTree` function from the renderer interface (it used to be conditionally injected behind `__IS_INTERNAL_MCP_BUILD__`). However `compiler/packages/react-mcp-server/src/tools/componentTree.ts` still calls `.get(1).__internal_only_getComponentTree()`, so this will now throw at runtime (method is `undefined`). Either update/remove the MCP server tool, or keep exposing a supported API for extracting the component tree.

How can I resolve this? If you propose a fix, please make it concise.

[everettbu]

Upstream PR was closed or merged. Code is synced via branch mirror.