feat: Generate vercel.json redirects from Netlify _redirects

Add sync-vercel-redirects.ts script that reads website/static/_redirects
(Netlify format), converts to Vercel format, and updates vercel.json.
This keeps _redirects as the single source of truth.

Add CI check that fails if vercel.json redirects drift out of sync.
Run 'yarn sync-redirects:vercel' after editing _redirects.

Author: mattcarrollcode

.github/workflows/pre-merge.yml

@@ -33,6 +33,29 @@ jobs:
       - name: Run plugins lint
         run: yarn lint:plugins
 
+  check-vercel-redirects:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v6
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v6
+        with:
+          node-version: "22"
+          cache: yarn
+
+      - name: Install dependencies
+        run: yarn install --immutable
+
+      - name: Check Vercel redirects are in sync
+        run: |
+          yarn sync-redirects:vercel
+          if ! git diff --exit-code vercel.json; then
+            echo "::error::vercel.json redirects are out of sync with _redirects. Run 'yarn sync-redirects:vercel' and commit."
+            exit 1
+          fi
+
   lint-website:
     runs-on: ubuntu-latest
     steps:

package.json

@@ -23,6 +23,7 @@
     "lint:website": "eslint ./website ./docs",
     "update-lock": "npx yarn-deduplicate",
     "check-dependencies": "manypkg check",
+    "sync-redirects:vercel": "node scripts/src/sync-vercel-redirects.ts",
     "build:vercel": "yarn --cwd website build:vercel",
     "build:vercel:fast": "yarn --cwd website build:vercel:fast",
     "dev:vercel": "vercel dev"

scripts/src/sync-vercel-redirects.ts

@@ -0,0 +1,124 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import fs from 'node:fs';
+import path from 'node:path';
+
+const REPO_ROOT = path.resolve(import.meta.dirname, '../..');
+const REDIRECTS_PATH = path.join(REPO_ROOT, 'website/static/_redirects');
+const VERSIONS_PATH = path.join(REPO_ROOT, 'website/versions.json');
+const VERCEL_JSON_PATH = path.join(REPO_ROOT, 'vercel.json');
+
+interface VercelRedirect {
+  source: string;
+  destination: string;
+  permanent: boolean;
+}
+
+function isPartialSegmentWildcard(source: string): boolean {
+  return source.split('/').some(seg => seg.includes('*') && seg !== '*');
+}
+
+function expandPartialWildcard(
+  source: string,
+  destination: string
+): VercelRedirect[] {
+  const segments = source.split('/');
+  const wildcardSeg = segments.find(seg => seg.includes('*') && seg !== '*')!;
+  const prefix = wildcardSeg.replace('*', '');
+
+  // Infer docs directory from destination path
+  // e.g. /docs/next/legacy/native-modules-:splat → docs/legacy/
+  const destDir = destination
+    .replace(/^\/docs\/next\//, '')
+    .replace(/\/[^/]*$/, '');
+  const searchDir = path.join(REPO_ROOT, 'docs', destDir);
+
+  let files: string[];
+  try {
+    files = fs
+      .readdirSync(searchDir)
+      .filter(f => f.startsWith(prefix) && /\.mdx?$/.test(f))
+      .map(f => f.replace(/\.mdx?$/, ''));
+  } catch {
+    console.warn(
+      `Warning: Could not read ${searchDir} for expanding ${source}`
+    );
+    return [];
+  }
+
+  return files.map(filename => {
+    const suffix = filename.slice(prefix.length);
+    return {
+      source: source.replace(`${prefix}*`, filename),
+      destination: destination.replace(':splat', suffix),
+      permanent: true,
+    };
+  });
+}
+
+function syncRedirects(): void {
+  const latestVersion: string = JSON.parse(
+    fs.readFileSync(VERSIONS_PATH, 'utf8')
+  )[0];
+
+  const lines = fs.readFileSync(REDIRECTS_PATH, 'utf8').split('\n');
+  const redirects: VercelRedirect[] = [];
+
+  for (const line of lines) {
+    const trimmed = line.trim();
+    if (!trimmed || trimmed.startsWith('#')) continue;
+
+    const parts = trimmed.split(/\s+/);
+    if (parts.length < 2) continue;
+
+    let [source, destination] = parts;
+
+    // Strip full URL sources to path only
+    if (source.startsWith('http://') || source.startsWith('https://')) {
+      try {
+        source = new URL(source).pathname;
+      } catch {
+        continue;
+      }
+    }
+
+    // Convert same-domain full URL destinations to relative paths
+    if (destination.startsWith('https://reactnative.dev/')) {
+      destination = destination.replace('https://reactnative.dev', '');
+    }
+
+    // Replace $LATEST_VERSION$ placeholder with actual version
+    source = source.replaceAll('$LATEST_VERSION$', latestVersion);
+    destination = destination.replaceAll('$LATEST_VERSION$', latestVersion);
+
+    // Handle partial-segment wildcards (e.g., native-modules-*)
+    // Vercel doesn't support wildcards within a path segment, so enumerate
+    if (isPartialSegmentWildcard(source)) {
+      redirects.push(...expandPartialWildcard(source, destination));
+      continue;
+    }
+
+    // Convert Netlify wildcard syntax to Vercel format
+    // Netlify: /* and :splat → Vercel: /:path*
+    source = source.replace(/\*$/, ':path*');
+    destination = destination.replace(':splat', ':path*');
+
+    redirects.push({source, destination, permanent: true});
+  }
+
+  const vercelJson = JSON.parse(fs.readFileSync(VERCEL_JSON_PATH, 'utf8'));
+  vercelJson.redirects = redirects;
+  fs.writeFileSync(
+    VERCEL_JSON_PATH,
+    JSON.stringify(vercelJson, null, 2) + '\n'
+  );
+
+  console.log(`Synced ${redirects.length} redirects to vercel.json`);
+}
+
+syncRedirects();