fs: fix always return promise from fs.openAsBlob

lib/fs.js

@@ -36,6 +36,7 @@ const {
   ObjectDefineProperty,
   Promise,
   PromisePrototypeThen,
+  PromiseReject,
   PromiseResolve,
   ReflectApply,
   SafeMap,
@@ -574,8 +575,12 @@ function openAsBlob(path, options = kEmptyObject) {
   // The underlying implementation here returns the Blob synchronously for now.
   // To give ourselves flexibility to maybe return the Blob asynchronously,
   // this API returns a Promise.
-  path = getValidatedPath(path);
-  return PromiseResolve(createBlobFromFilePath(path, { type }));
+  try {
+    path = getValidatedPath(path);
+    return PromiseResolve(createBlobFromFilePath(path, { type }));
+  } catch (error) {
+    return PromiseReject(error);
+  }
 }
 
 /**

test/parallel/test-fs-openasblob-promise-contract.js

@@ -0,0 +1,21 @@
+'use strict';
+
+const assert = require('assert');
+const fs = require('fs');
+
+// Verify invalid paths throw synchronously and return a Promise
+(async () => {
+  let promise;
+  assert.doesNotThrow(() => { promise = fs.openAsBlob('does-not-exist'); });
+  assert.strictEqual(typeof promise?.then, 'function');
+  await assert.rejects(promise, { code: 'ERR_INVALID_ARG_VALUE' });
+})();
+
+
+// Verify that invalid arguments throw synchronously and return a Promise
+(async () => {
+  let promise;
+  assert.doesNotThrow(() => { promise = fs.openAsBlob(123); });
+  assert.strictEqual(typeof promise?.then, 'function');
+  await assert.rejects(promise, { code: 'ERR_INVALID_ARG_TYPE' });
+})();