fixup: support detecting when a resolve hook returns a promise

Author: JakobJingleheimer

lib/internal/modules/esm/loader.js

@@ -164,8 +164,22 @@ function nextHookFactory(chain, meta, validate) {
  if (output?.shortCircuit === true) { meta.shortCircuited = true; }
  }
 
- if (output instanceof Promise) { // eslint-disable-line node-core/prefer-primordials
- output?.then(checkShortCircuited);
+ const then = output?.then;
+ if (typeof then === 'function') {
+ if (!meta.isChainAsync) {
+ throw ERR_INVALID_RETURN_VALUE(
+ 'an object',
+ // MUST use generatedHookIndex because the chain has already advanced,
+ // causing meta.hookIndex to advance
+ `${chain[generatedHookIndex].url} '${hookName}' hook's ${nextHookName}()`,
+ output,
+ );
+ }
+
+ ReflectApply(then, output, [
+ checkShortCircuited,
+ // TODO: handle error case
+ ]);
  } else {
  checkShortCircuited(output);
  }
@@ -568,6 +582,7 @@ class ESMLoader {
  hookErrIdentifier: '',
  hookIndex: chain.length - 1,
  hookName: 'load',
+ isChainAsync: true,
  shortCircuited: false,
  };
 
@@ -813,6 +828,7 @@ class ESMLoader {
  hookErrIdentifier: '',
  hookIndex: chain.length - 1,
  hookName: 'resolve',
+ isChainAsync: false,
  shortCircuited: false,
  };
  const context = {
@@ -822,14 +838,6 @@ class ESMLoader {
  };
 
  const validate = (hookErrIdentifier, output) => {
- if (output instanceof Promise) { // eslint-disable-line node-core/prefer-primordials
- throw ERR_INVALID_RETURN_VALUE(
- 'an object',
- hookErrIdentifier,
- output,
- );
- }
-
  const { 0: suppliedSpecifier, 1: ctx } = output;
 
  validateString(
@@ -847,7 +855,7 @@ class ESMLoader {
 
  if (
  typeof resolution !== 'object' || // [2]
- resolution instanceof Promise // eslint-disable-line node-core/prefer-primordials
+ typeof resolution?.then === 'function'
  ) {
  throw new ERR_INVALID_RETURN_VALUE(
  'an object',

test/es-module/test-esm-loader-chaining.mjs

@@ -166,11 +166,17 @@ const commonArgs = [
 }
 
 { // Verify error thrown for an async resolve hook
- const { status, stderr, stdout } = spawnSync(
+ const { status, stderr } = spawnSync(
  process.execPath,
  [
+ '--loader',
+ fixtures.fileURL('es-module-loaders', 'loader-resolve-shortcircuit.mjs'),
+ '--loader',
+ fixtures.fileURL('es-module-loaders', 'loader-resolve-42.mjs'),
  '--loader',
  fixtures.fileURL('es-module-loaders', 'loader-resolve-async-fn.mjs'),
+ '--loader',
+ fixtures.fileURL('es-module-loaders', 'loader-load-foo-or-42.mjs'),
  ...commonArgs,
  ],
  { encoding: 'utf8' },
@@ -180,7 +186,8 @@ const commonArgs = [
  assert.match(stderr, /Promise/);
  assert.match(stderr, /loader-resolve-async-fn\.mjs/);
  assert.match(stderr, /'resolve'/);
- assert.strictEqual(stdout, '');
+ // Cannot expect stdout to be empty because detecting whether a hook has
+ // returned a promise requires the hook to be executed
  assert.strictEqual(status, 1);
 }
 

test/fixtures/es-module-loaders/loader-resolve-async-fn.mjs

@@ -1,3 +1,3 @@
-export async function resolve() {
-return 'whatever';
+export async function resolve(specifier, context, next) {
+ return next(specifier, context);
 }