withResolvers shim

Author: BYK

package.json

@@ -143,7 +143,7 @@
     "@types/dompurify": "3.0.5"
   },
   "volta": {
-    "node": "22.16.0",
+    "node": "20.19.3",
     "yarn": "1.22.22"
   }
 }

scripts/generate-md-exports.mjs

@@ -126,14 +126,22 @@ async function createWork() {
 }
 
 const md5 = data => createHash('md5').update(data).digest('hex');
+const withResolvers = () => {
+  let resolve, reject;
+  const promise = new Promise((res, rej) => {
+    resolve = res;
+    reject = rej;
+  });
+  return {resolve, reject, promise};
+};
 
 async function genMDFromHTML(source, target, {cacheDir, noCache}) {
   const text = await readFile(source, {encoding: 'utf8'});
   const hash = md5(text);
   const cacheFile = path.join(cacheDir, hash);
   if (!noCache) {
     try {
-      const {resolve, reject, promise} = Promise.withResolvers();
+      const {resolve, reject, promise} = withResolvers();
       const reader = createReadStream(cacheFile);
       reader.on('error', reject);
       reader.pause();
@@ -185,7 +193,7 @@ async function genMDFromHTML(source, target, {cacheDir, noCache}) {
   const reader = Readable.from(data);
   reader.pause();
 
-  const {resolve, reject, promise} = Promise.withResolvers();
+  const {resolve, reject, promise} = withResolvers();
   const writer = createWriteStream(target, {
     encoding: 'utf8',
   });

src/mdx.ts

@@ -47,8 +47,20 @@ mkdirSync(CACHE_DIR, {recursive: true});
 
 const md5 = (data: BinaryLike) => createHash('md5').update(data).digest('hex');
 
+// TODO: Remove this shim when we upgrade to Node 22 on Vercel
+function withResolvers<T>() {
+  let resolve!: (value: T | PromiseLike<T>) => void;
+  let reject!: (reason?: any) => void;
+  const promise = new Promise<T>((res, rej) => {
+    resolve = res;
+    reject = rej;
+  });
+  return {resolve, reject, promise};
+};
+
+
 async function readCacheFile(file: string): Promise<string> {
-  const {resolve, reject, promise} = Promise.withResolvers<string>();
+  const {resolve, reject, promise} = withResolvers<string>();
 
   const reader = createReadStream(file);
   reader.on('error', reject);
@@ -71,7 +83,7 @@ async function readCacheFile(file: string): Promise<string> {
 }
 
 async function writeCacheFile(file: string, data: string) {
-  const {resolve, reject, promise} = Promise.withResolvers<void>();
+  const {resolve, reject, promise} = withResolvers<void>();
 
   const reader = Readable.from(data);
   reader.pause();