fix(codegen): read react-native.config.cjs so ESM projects are not silently skipped

[CAMOBAP]

Summary

readReactNativeConfig resolves the config with a single hardcoded extension:

const rnConfigFilePath = path.resolve(projectRoot, 'react-native.config.js');

A project whose package.json declares "type": "module" cannot use that filename. Node parses .js as ESM there, and the require() two lines below either throws or returns the wrong shape:

Config file	require() result
react-native.config.js, CommonJS body	throws ReferenceError: module is not defined in ES module scope — uncaught here, so codegen dies
react-native.config.js, ESM body	returns {__esModule, default}, so rnConfig.dependencies is undefined
react-native.config.cjs	returns the config correctly

.cjs is the only extension that is both require()-able and legal in an ESM package — and @react-native-community/cli already treats it as first-class:

// @react-native-community/cli-config/build/readConfigFromDisk.js
const searchPlacesForCJS = ['react-native.config.js', 'react-native.config.cjs', 'react-native.config.ts'];

added for react-native-community/cli#2167. Codegen has its own resolver, does not use cosmiconfig, and was never brought in line. This PR closes that gap.

Why it matters

Autolinking and codegen disagree about the same file, so the failure is silent and deferred. Autolinking reads the .cjs config and installs the pod; codegen doesn't, so it generates nothing for that library; the pod then compiles and its Fabric component includes a header that was never generated:

.../react/renderer/components/RNCSlider/RNCSliderShadowNode.h:5:10:
fatal error: 'react/renderer/components/RNCSlider/Props.h' file not found

Nothing in that error points at the config. findLibrariesFromReactNativeConfig bails via if (!rnConfig.dependencies) return []; without logging.

The other two config sources do not cover it:

• build/generated/autolinking/autolinking.json is written by use_native_modules! during pod install, so it is absent whenever codegen runs first (pipelines that codegen before installing pods, or generate-codegen-artifacts.js invoked directly).
• The package.json dependency scan only sees direct dependencies. A library reached through dependencies[...].root — the whole reason to write a config file — is by definition not one.

Changelog:

[General] [Fixed] - Codegen now also reads react-native.config.cjs, so libraries declared in it are no longer skipped in ESM projects

Test Plan

Four cases added to packages/react-native/scripts/codegen/__tests__/generate-artifacts-executor-test.js, following the existing mkdtempSync fixture pattern:

yarn jest packages/react-native/scripts/codegen/__tests__/generate-artifacts-executor-test.js

  readReactNativeConfig
    ✓ reads react-native.config.js
    ✓ reads react-native.config.cjs when there is no .js config
    ✓ prefers react-native.config.js when both exist
    ✓ returns an empty config when neither exists

Test Suites: 1 passed, 1 total
Tests:       48 passed, 48 total
Snapshots:   24 passed, 24 total

All 48 tests in the file pass, including the 24 existing snapshots — the change is additive for projects that have a .js config.

Negative control: with the utils.js change reverted and the tests left in place, the .cjs case fails as expected:

  ✕ reads react-native.config.cjs when there is no .js config
Tests: 1 failed, 47 skipped, 48 total

Notes

The log line in the else branch now names the directory searched rather than a single path, since there are two candidates:

-    codegenLog(`Could not find React Native config at: ${rnConfigFilePath}`);
+    codegenLog(`Could not find React Native config in: ${projectRoot}`);

Happy to extend this to .mjs / .ts to fully match the CLI's searchPlaces, but neither is a drop-in — .mjs cannot be require()d for the right default-export shape, and .ts needs a loader — so this PR keeps to the one case that is.

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[meta-codesync]

@vzaidman has imported this pull request. If you are a Meta employee, you can view this in D119188806.

[meta-codesync]

@vzaidman merged this pull request in 583c8f3.