feat(spm): drop consumer-side headers compose; don't ship build-only scripts

generate-spm-package previously composed the headers-spec layout on the consumer
side when the prebuilt artifacts lacked ReactNativeHeaders.xcframework. That
pulled the ios-prebuild build scripts (headers-compose and its deps) into the
published npm package, which in turn required the `plist` dependency at consumer
runtime.

The prebuilt core artifact ships React.xcframework AND ReactNativeHeaders.xcframework
together, so a consumer never needs to compose the layout. Remove the
consumer-side compose: fail with a clear error if ReactNativeHeaders is absent,
and stop listing scripts/ios-prebuild/* in the package files allowlist — those
are full-repo prebuild scripts, not consumer runtime code.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: chrfalch

packages/react-native/package.json

@@ -107,12 +107,6 @@
     "scripts/hermes/hermes-utils.js",
     "scripts/hermes/prepare-hermes-for-build.js",
     "scripts/ios-configure-glog.sh",
-    "scripts/ios-prebuild/headers-compose.js",
-    "scripts/ios-prebuild/headers-config.js",
-    "scripts/ios-prebuild/headers-inventory.js",
-    "scripts/ios-prebuild/headers-spec.js",
-    "scripts/ios-prebuild/headers.js",
-    "scripts/ios-prebuild/utils.js",
     "scripts/native_modules.rb",
     "scripts/node-binary.sh",
     "scripts/packager-reporter.js",

packages/react-native/scripts/spm/__tests__/generate-spm-package-test.js

@@ -157,7 +157,7 @@ describe('main', () => {
     return dir;
   }
 
-  function run(artifactsDir /*:: ?: ?string */, deps /*:: ?: Object */) {
+  function run(artifactsDir /*:: ?: ?string */) {
     const argv = [
       '--app-root',
       appRoot,
@@ -169,23 +169,20 @@ describe('main', () => {
     if (artifactsDir != null) {
       argv.push('--artifacts-dir', artifactsDir);
     }
-    main(argv, deps);
+    main(argv);
   }
 
   it('generates Package.swift + symlinks when headers ship in the slot', () => {
     writeAppPkg();
-    // ReactNativeHeaders present → the headers composer is never consulted.
     const artifactsDir = writeArtifacts([
       'React',
       'ReactNativeDependencies',
       'hermes-engine',
       'ReactNativeHeaders',
     ]);
     try {
-      const ensureHeadersLayout = jest.fn();
-      run(artifactsDir, {ensureHeadersLayout});
+      run(artifactsDir);
 
-      expect(ensureHeadersLayout).not.toHaveBeenCalled();
       expect(process.exitCode).toBeUndefined();
 
       const pkgSwift = path.join(
@@ -213,46 +210,27 @@ describe('main', () => {
     }
   });
 
-  it('composes the headers layout when ReactNativeHeaders is absent', () => {
+  it('errors when ReactNativeHeaders is absent (no consumer-side compose)', () => {
     writeAppPkg();
+    // Artifacts WITHOUT ReactNativeHeaders: the consumer does not compose the
+    // layout locally, it fails with a clear error instead.
     const artifactsDir = writeArtifacts([
       'React',
       'ReactNativeDependencies',
       'hermes-engine',
     ]);
-    // Targets the injected composer points the React/headers symlinks at.
-    const composedReact = path.join(artifactsDir, 'composed-React.xcframework');
-    const composedHeaders = path.join(
-      artifactsDir,
-      'composed-ReactNativeHeaders.xcframework',
-    );
-    fs.mkdirSync(composedReact, {recursive: true});
-    fs.mkdirSync(composedHeaders, {recursive: true});
     try {
-      const ensureHeadersLayout = jest.fn(() => ({
-        reactXcfw: composedReact,
-        headersXcfw: composedHeaders,
-      }));
-      run(artifactsDir, {ensureHeadersLayout});
-
-      expect(ensureHeadersLayout).toHaveBeenCalledTimes(1);
-      expect(process.exitCode).toBeUndefined();
+      run(artifactsDir);
 
-      const headersLink = path.join(
-        appRoot,
-        'build',
-        'xcframeworks',
-        'ReactNativeHeaders.xcframework',
-      );
-      expect(fs.lstatSync(headersLink).isSymbolicLink()).toBe(true);
-      expect(fs.readlinkSync(headersLink)).toBe(composedHeaders);
-      // The React symlink is re-pointed at the composed override, not the raw entry.
+      expect(process.exitCode).toBe(1);
+      // No package is generated when the artifacts are incomplete.
       expect(
-        fs.readlinkSync(
-          path.join(appRoot, 'build', 'xcframeworks', 'React.xcframework'),
+        fs.existsSync(
+          path.join(appRoot, 'build', 'xcframeworks', 'Package.swift'),
         ),
-      ).toBe(composedReact);
+      ).toBe(false);
     } finally {
+      process.exitCode = undefined;
       fs.rmSync(artifactsDir, {recursive: true, force: true});
     }
   });

packages/react-native/scripts/spm/generate-spm-package.js

@@ -224,10 +224,7 @@ ${binaryTargets}
 `;
 }
 
-function main(
-  argv /*:: ?: Array<string> */,
-  deps /*:: ?: {ensureHeadersLayout?: (string, string, string) => {reactXcfw: string, headersXcfw: string}} */,
-) /*: void */ {
+function main(argv /*:: ?: Array<string> */) /*: void */ {
   const args = parseArgs(argv ?? process.argv.slice(2));
   // Ensure appRoot is always absolute so path.join/path.resolve produce absolute paths
   // even when called with --app-root . or other relative paths.
@@ -307,27 +304,21 @@ function main(
     const xcfwLinksDir = path.join(appRoot, 'build', 'xcframeworks');
     fs.mkdirSync(xcfwLinksDir, {recursive: true});
 
-    // The spec layout (headers-spec.js) is what
-    // consumers compile against. When the slot's artifacts.json already
-    // carries ReactNativeHeaders (published or local tarball via
-    // download-spm-artifacts), the artifacts ship the layout and are used
-    // as-is. Otherwise the layout is COMPOSED locally from the slot's
-    // React + deps artifacts (binaries untouched; headers re-projected) —
-    // fast, marker-cached, re-run safe.
-    const rnPkgRoot = path.resolve(__dirname, '..', '..');
-    const overrides /*: {[string]: string} */ = {};
+    // Consumers compile against the spec layout (headers-spec.js, emitted at
+    // prebuild time). The prebuilt core artifact must ship React.xcframework AND
+    // ReactNativeHeaders.xcframework together — published tarballs and
+    // download-spm-artifacts include both. The layout is NOT composed on the
+    // consumer side (that needs the full RN repo / ios-prebuild build scripts,
+    // which the npm package deliberately does not ship).
     if (raw.ReactNativeHeaders == null) {
-      const ensureHeadersLayout =
-        deps?.ensureHeadersLayout ??
-        // $FlowFixMe[cannot-resolve-module] cross-dir require into ios-prebuild
-        require('../ios-prebuild/headers-compose').ensureHeadersLayout;
-      const composed = ensureHeadersLayout(
-        artifactsDir ?? path.dirname(String(raw.React?.xcframeworkPath ?? '')),
-        rnPkgRoot,
-        path.join(rnPkgRoot, 'build', 'headers'),
+      console.error(
+        'Prebuilt artifacts are missing ReactNativeHeaders.xcframework — the ' +
+          'React Native core artifact must ship it alongside React.xcframework. ' +
+          'Re-download or rebuild the artifact (or point --artifacts-dir at a ' +
+          'complete slot).',
       );
-      overrides.React = composed.reactXcfw;
-      overrides.ReactNativeHeaders = composed.headersXcfw;
+      process.exitCode = 1;
+      return;
     }
 
     const names /*: Array<string> */ = [];
@@ -346,10 +337,7 @@ function main(
     };
     // $FlowFixMe[incompatible-use] Object.entries values typed as mixed
     for (const [name, entry] of Object.entries(raw)) {
-      linkOne(name, overrides[name] ?? entry.xcframeworkPath);
-    }
-    if (overrides.ReactNativeHeaders != null) {
-      linkOne('ReactNativeHeaders', overrides.ReactNativeHeaders);
+      linkOne(name, entry.xcframeworkPath);
     }
 
     // Pass the absolute artifacts dir so the binary target paths reference the