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Tooling in the ecosystem have been using the __esModule property to
recognize transpiled ESM in consuming code. For example, a 'log'
package written in ESM:
export function log(val) { console.log(val); }
Can be transpiled as:
exports.__esModule = true;
exports.default = function log(val) { console.log(val); }
The consuming code may be written like this in ESM:
import log from 'log'
Which gets transpiled to:
const _mod = require('log');
const log = _mod.__esModule ? _mod.default : _mod;
So to allow transpiled consuming code to recognize require()'d real ESM
as ESM and pick up the default exports, we add a __esModule property by
building a source text module facade for any module that has a default
export and add .__esModule = true to the exports. We don't do this to
modules that don't have default exports to avoid the unnecessary
overhead. This maintains the enumerability of the re-exported names
and the live binding of the exports.
The source of the facade is defined as a constant per-isolate property
required_module_facade_source_string, which looks like this
export * from 'original';
export { default } from 'original';
export const __esModule = true;
And the 'original' module request is always resolved by
createRequiredModuleFacade() to wrap which is a ModuleWrap wrapping
over the original module.
PR-URL: https://github.com/nodejs/node/pull/52166
Refs: https://github.com/nodejs/node/issues/52134
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Filip Skokan <panva.ip@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
32 lines
1.0 KiB
JavaScript
32 lines
1.0 KiB
JavaScript
// Flags: --experimental-require-module
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'use strict';
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// Tests that previously dynamically import()'ed results are reference equal to
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// require()'d results.
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const common = require('../common');
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const assert = require('assert');
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const path = require('path');
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const { pathToFileURL } = require('url');
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(async () => {
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const modules = [
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'../fixtures/es-module-loaders/module-named-exports.mjs',
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'../fixtures/es-modules/import-esm.mjs',
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'../fixtures/es-modules/require-cjs.mjs',
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'../fixtures/es-modules/cjs-exports.mjs',
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'../common/index.mjs',
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'../fixtures/es-modules/package-type-module/index.js',
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];
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for (const id of modules) {
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const url = pathToFileURL(path.resolve(__dirname, id));
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const imported = await import(url);
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const required = require(id);
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common.expectRequiredModule(required, imported);
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}
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const id = '../fixtures/es-modules/data-import.mjs';
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const imported = await import(id);
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const required = require(id);
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assert.strictEqual(imported.data, required.data);
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})().then(common.mustCall());
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