esm: rewrite loader hooks test

Rewrite the test that validates that custom loader hooks are called from
being a test that depends on internals to one that spawns a child
process and checks its output to confirm expected behavior.

PR-URL: https://github.com/nodejs/node/pull/46016
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Jacob Smith <jacob@frende.me>

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

@@ -1,83 +1,26 @@
-// Flags: --expose-internals
-import { mustCall } from '../common/index.mjs';
-import esmLoaderModule from 'internal/modules/esm/loader';
-import assert from 'assert';
+import { spawnPromisified } from '../common/index.mjs';
+import * as fixtures from '../common/fixtures.mjs';
+import assert from 'node:assert';
+import { execPath } from 'node:process';
+import { describe, it } from 'node:test';
 
-const { ESMLoader } = esmLoaderModule;
-
-/**
- * Verify custom hooks are called with appropriate arguments.
- */
-{
-  const esmLoader = new ESMLoader();
-
-  const originalSpecifier = 'foo/bar';
-  const importAssertions = {
-    __proto__: null,
-    type: 'json',
-  };
-  const parentURL = 'file:///entrypoint.js';
-  const resolvedURL = 'file:///foo/bar.js';
-  const suggestedFormat = 'test';
-
-  function resolve(specifier, context, defaultResolve) {
-    assert.strictEqual(specifier, originalSpecifier);
-    // Ensure `context` has all and only the properties it's supposed to
-    assert.deepStrictEqual(Object.keys(context), [
-      'conditions',
-      'importAssertions',
-      'parentURL',
+describe('Loader hooks', () => {
+  it('are called with all expected arguments', async () => {
+    const { code, signal, stdout, stderr } = await spawnPromisified(execPath, [
+      '--no-warnings',
+      '--experimental-loader',
+      fixtures.fileURL('/es-module-loaders/hooks-input.mjs'),
+      fixtures.path('/es-modules/json-modules.mjs'),
     ]);
-    assert.ok(Array.isArray(context.conditions));
-    assert.deepStrictEqual(context.importAssertions, importAssertions);
-    assert.strictEqual(context.parentURL, parentURL);
-    assert.strictEqual(typeof defaultResolve, 'function');
 
-    return {
-      format: suggestedFormat,
-      shortCircuit: true,
-      url: resolvedURL,
-    };
-  }
+    assert.strictEqual(stderr, '');
+    assert.strictEqual(code, 0);
+    assert.strictEqual(signal, null);
 
-  function load(resolvedURL, context, defaultLoad) {
-    assert.strictEqual(resolvedURL, resolvedURL);
-    assert.ok(new URL(resolvedURL));
-    // Ensure `context` has all and only the properties it's supposed to
-    assert.deepStrictEqual(Object.keys(context), [
-      'format',
-      'importAssertions',
-    ]);
-    assert.strictEqual(context.format, suggestedFormat);
-    assert.deepStrictEqual(context.importAssertions, importAssertions);
-    assert.strictEqual(typeof defaultLoad, 'function');
-
-    // This doesn't matter (just to avoid errors)
-    return {
-      format: 'module',
-      shortCircuit: true,
-      source: '',
-    };
-  }
-
-  const customLoader = [
-    {
-      exports: {
-        // Ensure ESMLoader actually calls the custom hooks
-        resolve: mustCall(resolve),
-        load: mustCall(load),
-      },
-      url: import.meta.url,
-    },
-  ];
-
-  esmLoader.addCustomLoaders(customLoader);
-
-  // Manually trigger hooks (since ESMLoader is not actually running)
-  const job = await esmLoader.getModuleJob(
-    originalSpecifier,
-    parentURL,
-    importAssertions,
-  );
-  await job.modulePromise;
-}
+    const lines = stdout.split('\n');
+    assert.match(lines[0], /{"url":"file:\/\/\/.*\/json-modules\.mjs","format":"test","shortCircuit":true}/);
+    assert.match(lines[1], /{"source":{"type":"Buffer","data":\[.*\]},"format":"module","shortCircuit":true}/);
+    assert.match(lines[2], /{"url":"file:\/\/\/.*\/experimental\.json","format":"test","shortCircuit":true}/);
+    assert.match(lines[3], /{"source":{"type":"Buffer","data":\[.*\]},"format":"json","shortCircuit":true}/);
+  });
+});

test/fixtures/es-module-loaders/hooks-input.mjs

@@ -0,0 +1,91 @@
+// This is expected to be used by test-esm-loader-hooks.mjs via:
+// node --loader ./test/fixtures/es-module-loaders/hooks-input.mjs ./test/fixtures/es-modules/json-modules.mjs
+
+import assert from 'assert';
+import { readFile } from 'fs/promises';
+import { fileURLToPath } from 'url';
+
+
+let resolveCalls = 0;
+let loadCalls = 0;
+
+export async function resolve(specifier, context, next) {
+  resolveCalls++;
+  let url;
+
+  if (resolveCalls === 1) {
+    url = new URL(specifier).href;
+    assert.match(specifier, /json-modules\.mjs$/);
+    assert.strictEqual(context.parentURL, undefined);
+    assert.deepStrictEqual(context.importAssertions, {
+      __proto__: null,
+    });
+  } else if (resolveCalls === 2) {
+    url = new URL(specifier, context.parentURL).href;
+    assert.match(specifier, /experimental\.json$/);
+    assert.match(context.parentURL, /json-modules\.mjs$/);
+    assert.deepStrictEqual(context.importAssertions, {
+      __proto__: null,
+      type: 'json',
+    });
+  }
+
+  // Ensure `context` has all and only the properties it's supposed to
+  assert.deepStrictEqual(Reflect.ownKeys(context), [
+    'conditions',
+    'importAssertions',
+    'parentURL',
+  ]);
+  assert.ok(Array.isArray(context.conditions));
+  assert.strictEqual(typeof next, 'function');
+
+  const returnValue = {
+    url,
+    format: 'test',
+    shortCircuit: true,
+  }
+
+  console.log(JSON.stringify(returnValue)); // For the test to validate when it parses stdout
+
+  return returnValue;
+}
+
+export async function load(url, context, next) {
+  loadCalls++;
+  const source = await readFile(fileURLToPath(url));
+  let format;
+
+  if (loadCalls === 1) {
+    assert.match(url, /json-modules\.mjs$/);
+    assert.deepStrictEqual(context.importAssertions, {
+      __proto__: null,
+    });
+    format = 'module';
+  } else if (loadCalls === 2) {
+    assert.match(url, /experimental\.json$/);
+    assert.deepStrictEqual(context.importAssertions, {
+      __proto__: null,
+      type: 'json',
+    });
+    format = 'json';
+  }
+
+  assert.ok(new URL(url));
+  // Ensure `context` has all and only the properties it's supposed to
+  assert.deepStrictEqual(Object.keys(context), [
+    'format',
+    'importAssertions',
+  ]);
+  assert.strictEqual(context.format, 'test');
+  assert.strictEqual(typeof next, 'function');
+
+  const returnValue = {
+    source,
+    format,
+    shortCircuit: true,
+  };
+
+  console.log(JSON.stringify(returnValue)); // For the test to validate when it parses stdout
+
+  return returnValue;
+}