esm: isolate globalPreload

Author: GeoffreyBooth

lib/internal/modules/esm/hooks.js

@@ -73,6 +73,7 @@ let importMetaInitializer;
 
 /**
  * @typedef {object} ExportedHooks
+ * @property {Function} initialize Customizations setup hook.
  * @property {Function} globalPreload Global preload hook.
  * @property {Function} resolve Resolve hook.
  * @property {Function} load Load hook.

lib/internal/modules/esm/worker.js

@@ -74,7 +74,9 @@ function wrapMessage(status, body) {
 }
 
 async function customizedModuleWorker(lock, syncCommPort, errorHandler) {
-  let hooks, preloadScripts, initializationError;
+  let hooks;
+  let preloadScripts;
+  let initializationError;
   let hasInitializationError = false;
 
   {

test/es-module/test-esm-loader-globalpreload-hook.mjs

@@ -0,0 +1,131 @@
+import { spawnPromisified } from '../common/index.mjs';
+import * as fixtures from '../common/fixtures.mjs';
+import assert from 'node:assert';
+import os from 'node:os';
+import { execPath } from 'node:process';
+import { describe, it } from 'node:test';
+
+describe('globalPreload hook', () => {
+  it('should not emit deprecation warning when initialize is supplied', async () => {
+    const { stderr } = await spawnPromisified(execPath, [
+      '--experimental-loader',
+      'data:text/javascript,export function globalPreload(){}export function initialize(){}',
+      fixtures.path('empty.js'),
+    ]);
+
+    assert.doesNotMatch(stderr, /`globalPreload` is an experimental feature/);
+  });
+
+  it('should handle globalPreload returning undefined', async () => {
+    const { code, signal, stdout, stderr } = await spawnPromisified(execPath, [
+      '--no-warnings',
+      '--experimental-loader',
+      'data:text/javascript,export function globalPreload(){}',
+      fixtures.path('empty.js'),
+    ]);
+
+    assert.strictEqual(stderr, '');
+    assert.strictEqual(stdout, '');
+    assert.strictEqual(code, 0);
+    assert.strictEqual(signal, null);
+  });
+
+  it('should handle loading node:test', async () => {
+    const { code, signal, stdout, stderr } = await spawnPromisified(execPath, [
+      '--no-warnings',
+      '--experimental-loader',
+      'data:text/javascript,export function globalPreload(){return `getBuiltin("node:test")()`}',
+      fixtures.path('empty.js'),
+    ]);
+
+    assert.strictEqual(stderr, '');
+    assert.match(stdout, /\n# pass 1\r?\n/);
+    assert.strictEqual(code, 0);
+    assert.strictEqual(signal, null);
+  });
+
+  it('should handle loading node:os with node: prefix', async () => {
+    const { code, signal, stdout, stderr } = await spawnPromisified(execPath, [
+      '--no-warnings',
+      '--experimental-loader',
+      'data:text/javascript,export function globalPreload(){return `console.log(getBuiltin("node:os").arch())`}',
+      fixtures.path('empty.js'),
+    ]);
+
+    assert.strictEqual(stderr, '');
+    assert.strictEqual(stdout.trim(), os.arch());
+    assert.strictEqual(code, 0);
+    assert.strictEqual(signal, null);
+  });
+
+  // `os` is used here because it's simple and not mocked (the builtin module otherwise doesn't matter).
+  it('should handle loading builtin module without node: prefix', async () => {
+    const { code, signal, stdout, stderr } = await spawnPromisified(execPath, [
+      '--no-warnings',
+      '--experimental-loader',
+      'data:text/javascript,export function globalPreload(){return `console.log(getBuiltin("os").arch())`}',
+      fixtures.path('empty.js'),
+    ]);
+
+    assert.strictEqual(stderr, '');
+    assert.strictEqual(stdout.trim(), os.arch());
+    assert.strictEqual(code, 0);
+    assert.strictEqual(signal, null);
+  });
+
+  it('should throw when loading node:test without node: prefix', async () => {
+    const { code, signal, stdout, stderr } = await spawnPromisified(execPath, [
+      '--no-warnings',
+      '--experimental-loader',
+      'data:text/javascript,export function globalPreload(){return `getBuiltin("test")()`}',
+      fixtures.path('empty.js'),
+    ]);
+
+    assert.match(stderr, /ERR_UNKNOWN_BUILTIN_MODULE/);
+    assert.strictEqual(stdout, '');
+    assert.strictEqual(code, 1);
+    assert.strictEqual(signal, null);
+  });
+
+  it('should register globals set from globalPreload', async () => {
+    const { code, signal, stdout, stderr } = await spawnPromisified(execPath, [
+      '--no-warnings',
+      '--experimental-loader',
+      'data:text/javascript,export function globalPreload(){return "this.myGlobal=4"}',
+      '--print', 'myGlobal',
+    ]);
+
+    assert.strictEqual(stderr, '');
+    assert.strictEqual(stdout.trim(), '4');
+    assert.strictEqual(code, 0);
+    assert.strictEqual(signal, null);
+  });
+
+  it('should log console.log calls returned from globalPreload', async () => {
+    const { code, signal, stdout, stderr } = await spawnPromisified(execPath, [
+      '--no-warnings',
+      '--experimental-loader',
+      'data:text/javascript,export function globalPreload(){return `console.log("Hello from globalPreload")`}',
+      fixtures.path('empty.js'),
+    ]);
+
+    assert.strictEqual(stderr, '');
+    assert.strictEqual(stdout.trim(), 'Hello from globalPreload');
+    assert.strictEqual(code, 0);
+    assert.strictEqual(signal, null);
+  });
+
+  it('should crash if globalPreload returns code that throws', async () => {
+    const { code, signal, stdout, stderr } = await spawnPromisified(execPath, [
+      '--no-warnings',
+      '--experimental-loader',
+      'data:text/javascript,export function globalPreload(){return `throw new Error("error from globalPreload")`}',
+      fixtures.path('empty.js'),
+    ]);
+
+    assert.match(stderr, /error from globalPreload/);
+    assert.strictEqual(stdout, '');
+    assert.strictEqual(code, 1);
+    assert.strictEqual(signal, null);
+  });
+});

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

@@ -423,7 +423,7 @@ describe('Loader hooks', { concurrency: true }, () => {
   });
 
   describe('globalPreload', () => {
-    it('should emit deprecation warning', async () => {
+    it('should emit warning', async () => {
       const { stderr } = await spawnPromisified(execPath, [
         '--experimental-loader',
         'data:text/javascript,export function globalPreload(){}',

test/fixtures/es-module-loaders/loader-this-value-inside-hook-functions.mjs

@@ -8,7 +8,7 @@ export function load(url, _, next) {
   return next(url);
 }
 
-export function globalPreload() {
+export function initialize() {
   if (this != null) throw new Error('hook function must not be bound to ESMLoader instance');
   return "";
 }