fix(promise): capture stacks on an Error for Bun

lib/promise/capture_local_err.js

@@ -2,7 +2,9 @@
 
 /** @param {Function} constructorOpt Passed to Error.captureStackTrace (omit this frame from stacks). */
 function captureStackHolder(constructorOpt) {
-  const holder = {};
+  // Bun's Error.prepareStackTrace requires an Error instance. A plain object
+  // works in V8, but throws "First argument must be an Error object" there.
+  const holder = new Error();
   Error.captureStackTrace(holder, constructorOpt);
   return holder;
 }
@@ -12,7 +14,7 @@ function captureStackHolder(constructorOpt) {
  * callback error instance and its MySQL fields.
  *
  * @param {Error} err
- * @param {{ stack?: string }} holder
+ * @param {Error} holder
  */
 function applyCapturedStack(err, holder) {
   const stack = holder && holder.stack;

test/unit/test-capture-local-err.test.mts

@@ -0,0 +1,50 @@
+import { describe, it, strict } from 'poku';
+import captureLocalErr from '../../lib/promise/capture_local_err.js';
+
+const { captureStackHolder, applyCapturedStack } = captureLocalErr;
+
+await describe('capture_local_err', async () => {
+  await it('should capture on an Error so Bun prepareStackTrace can format it', () => {
+    const original = Error.prepareStackTrace;
+    let seenErr: Error | undefined;
+    Error.prepareStackTrace = (err, traces) => {
+      seenErr = err;
+      if (!(err instanceof Error)) {
+        throw new TypeError('First argument must be an Error object failed');
+      }
+      return original ? original.call(Error, err, traces) : String(err.stack);
+    };
+    try {
+      const holder = captureStackHolder(captureStackHolder);
+      strict.ok(holder instanceof Error, 'holder should be an Error instance');
+      const stack = holder.stack ?? '';
+      strict.equal(typeof holder.stack, 'string');
+      strict.ok(stack.length > 0);
+      strict.ok(seenErr instanceof Error);
+    } finally {
+      Error.prepareStackTrace = original;
+    }
+  });
+
+  await it('should keep the callback error identity and rewrite its stack', () => {
+    function captureHere() {
+      return captureStackHolder(captureHere);
+    }
+    const holder = captureHere();
+    const err = new Error('ER_PARSE_ERROR: syntax error') as Error & {
+      code?: string;
+    };
+    err.code = 'ER_PARSE_ERROR';
+    applyCapturedStack(err, holder);
+    strict.equal(err.code, 'ER_PARSE_ERROR');
+    const stack = err.stack ?? '';
+    strict.ok(
+      stack.startsWith('Error: ER_PARSE_ERROR: syntax error'),
+      `unexpected stack:\n${stack}`
+    );
+    strict.ok(
+      stack.includes('test-capture-local-err.test.mts'),
+      `expected this test file in the rewritten stack:\n${stack}`
+    );
+  });
+});