feat(spm): treat package.json codegenConfig as an implicit React-core dep

New-Architecture libraries (react-native-svg, …) declare their React-core
dependency only through the `install_modules_dependencies(s)` podspec helper —
which auto-adds React-Core / React-RCTFabric / React-Codegen at install time —
rather than an explicit `s.dependency "React-Core"`. We strip that helper when
evaluating the podspec, so the React-core dependency never surfaced in
model.dependencies and `coreReactNative` stayed false. The scaffolded manifest
then declared no dependencies at all, and the lib's Fabric sources failed with:

    RNSVGShadowNodes.cpp:1:10: fatal error:
      'react/renderer/components/rnsvg/ShadowNodes.h' file not found

That generated header lives in the per-app React-GeneratedCode package (the
`ReactAppHeaders` target vends `react/renderer/components/<name>/…`), which the
lib can only reach via an SPM dependency — SwiftPM forbids a headerSearchPath
from escaping the package root, so cross-package headers must come through a
dependency's publicHeadersPath.

Fix: detect a `codegenConfig` block in the dep's package.json — RN's
authoritative marker that a library participates in the New Architecture /
codegen — and treat it as an implicit React-core dependency. That makes the
scaffolder emit the existing `.package(name: "React-GeneratedCode", …)` +
`.product(name: "ReactAppHeaders", …)` wiring, so the generated component
headers resolve.

Verified: react-native-svg now BUILD SUCCEEDED via the scaffolder on a real
RN 0.87 app (previously stopped at the ShadowNodes.h codegen header).
SCAFFOLDER_VERSION bumped to 17. 401 spm tests green (2 new).

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

Author: chrfalch

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

@@ -321,6 +321,45 @@ describe('translatePodspecToSpmTarget', () => {
     expect(spec.siblingNames).toEqual(['react-native-worklets']);
   });
 
+  it('treats a package.json codegenConfig as an implicit React-core dep (New-Arch libs strip install_modules_dependencies — svg shape)', () => {
+    // svg declares its React-core dep only via install_modules_dependencies(s),
+    // which we strip — so model.dependencies has NO React-Core. The codegenConfig
+    // marker is what tells us it still needs the React-GeneratedCode package.
+    const root = fs.mkdtempSync(path.join(os.tmpdir(), 'codegen-dep-'));
+    try {
+      fs.writeFileSync(
+        path.join(root, 'package.json'),
+        JSON.stringify({name: 'react-native-svg', codegenConfig: {name: 'rnsvg'}}),
+      );
+      const model = podspec({dependencies: []}); // nothing explicit
+      const spec = translatePodspecToSpmTarget(
+        model,
+        autolinkedDep({name: 'react-native-svg', root}),
+      );
+      expect(spec.coreReactNative).toBe(true);
+    } finally {
+      fs.rmSync(root, {recursive: true, force: true});
+    }
+  });
+
+  it('does NOT force coreReactNative for a non-codegen dep with no React deps', () => {
+    const root = fs.mkdtempSync(path.join(os.tmpdir(), 'no-codegen-dep-'));
+    try {
+      fs.writeFileSync(
+        path.join(root, 'package.json'),
+        JSON.stringify({name: 'react-native-foo'}), // no codegenConfig
+      );
+      const model = podspec({dependencies: []});
+      const spec = translatePodspecToSpmTarget(
+        model,
+        autolinkedDep({name: 'react-native-foo', root}),
+      );
+      expect(spec.coreReactNative).toBe(false);
+    } finally {
+      fs.rmSync(root, {recursive: true, force: true});
+    }
+  });
+
   it('warns + drops unknown non-RN dependencies (MMKV, AFNetworking)', () => {
     const model = podspec({dependencies: ['MMKV', 'AFNetworking']});
     const spec = translatePodspecToSpmTarget(model, autolinkedDep());

packages/react-native/scripts/spm/scaffold-package-swift.js

@@ -93,7 +93,7 @@ const {log} = makeLogger('scaffold-package-swift');
 // defines from pod_target_xcconfig emitted as `.define(...)`. v13: ObjC(++)
 // targets get an ambient-import prefix header (Foundation/UIKit) `-include`d,
 // replacing CocoaPods' generated prefix.pch.
-const SCAFFOLDER_VERSION = 16;
+const SCAFFOLDER_VERSION = 17;
 const SCAFFOLDER_VERSION_LINE_RE = /^\/\/ AUTO-SCAFFOLDED-VERSION: (\d+)$/m;
 
 const AUTOGEN_MARKER =
@@ -147,6 +147,24 @@ function isReactCoreDep(name /*: string */) /*: boolean */ {
   return REACT_CORE_DEP_PREFIXES.some(p => name.startsWith(p));
 }
 
+// True when the dep ships a `codegenConfig` in package.json — RN's standard
+// marker that the library participates in the New Architecture / codegen. Such
+// a lib's Fabric sources include the app-generated component headers
+// (`<react/renderer/components/<name>/ShadowNodes.h>` etc.), which are vended by
+// the per-app React-GeneratedCode package — so it implicitly depends on React
+// core even when its podspec only wires that via `install_modules_dependencies`
+// (which we strip). Safe/quiet: a missing or unparseable package.json → false.
+function depHasCodegenConfig(depRoot /*: string */) /*: boolean */ {
+  try {
+    const pkg = JSON.parse(
+      fs.readFileSync(path.join(depRoot, 'package.json'), 'utf8'),
+    );
+    return pkg != null && pkg.codegenConfig != null;
+  } catch {
+    return false;
+  }
+}
+
 // Every subdirectory (relative to depRoot) under depRoot/base, recursively —
 // used to expand a CocoaPods `path/**` recursive header search path into the
 // concrete dirs SPM needs (SPM has no recursive search-path syntax). Skips
@@ -325,6 +343,23 @@ function translatePodspecToSpmTarget(
     }
   }
 
+  // New-Architecture libraries declare their React-core dependency via the
+  // `install_modules_dependencies(s)` podspec helper (which auto-adds
+  // React-Core / React-RCTFabric / React-Codegen), NOT an explicit
+  // `s.dependency "React-Core"`. We strip that helper when evaluating the
+  // podspec, so the React-core dependency never surfaces in model.dependencies
+  // and `coreReactNative` would stay false. The authoritative, RN-standard
+  // marker for "this lib participates in the New Architecture / codegen" is a
+  // `codegenConfig` block in package.json — when present, the app's codegen has
+  // generated `react/renderer/components/<name>/{ShadowNodes,Props,…}.h` that
+  // the lib's Fabric sources include via angle brackets. Those generated
+  // headers live in the per-app React-GeneratedCode package, so the lib must
+  // depend on it (and, transitively, on React core). Treat codegenConfig as
+  // an implicit React-core dependency.
+  if (!coreReactNative && depHasCodegenConfig(dep.root)) {
+    coreReactNative = true;
+  }
+
   // SPM's `sources:` field does NOT accept CocoaPods-style globs — it wants
   // a list of explicit file paths (relative to the target's `path:`).
   // Expand the podspec globs against the actual filesystem so the emitted