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This patch adds `require()` support for synchronous ESM graphs under
the flag `--experimental-require-module`
This is based on the the following design aspect of ESM:
- The resolution can be synchronous (up to the host)
- The evaluation of a synchronous graph (without top-level await) is
also synchronous, and, by the time the module graph is instantiated
(before evaluation starts), this is is already known.
If `--experimental-require-module` is enabled, and the ECMAScript
module being loaded by `require()` meets the following requirements:
- Explicitly marked as an ES module with a `"type": "module"` field in
the closest package.json or a `.mjs` extension.
- Fully synchronous (contains no top-level `await`).
`require()` will load the requested module as an ES Module, and return
the module name space object. In this case it is similar to dynamic
`import()` but is run synchronously and returns the name space object
directly.
```mjs
// point.mjs
export function distance(a, b) {
return (b.x - a.x) ** 2 + (b.y - a.y) ** 2;
}
class Point {
constructor(x, y) { this.x = x; this.y = y; }
}
export default Point;
```
```cjs
const required = require('./point.mjs');
// [Module: null prototype] {
// default: [class Point],
// distance: [Function: distance]
// }
console.log(required);
(async () => {
const imported = await import('./point.mjs');
console.log(imported === required); // true
})();
```
If the module being `require()`'d contains top-level `await`, or the
module graph it `import`s contains top-level `await`,
[`ERR_REQUIRE_ASYNC_MODULE`][] will be thrown. In this case, users
should load the asynchronous module using `import()`.
If `--experimental-print-required-tla` is enabled, instead of throwing
`ERR_REQUIRE_ASYNC_MODULE` before evaluation, Node.js will evaluate the
module, try to locate the top-level awaits, and print their location to
help users fix them.
PR-URL: https://github.com/nodejs/node/pull/51977
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
52 lines
1.4 KiB
JavaScript
52 lines
1.4 KiB
JavaScript
'use strict';
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const { BuiltinModule: { normalizeRequirableId } } = require('internal/bootstrap/realm');
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const { Module, wrapSafe } = require('internal/modules/cjs/loader');
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const { codes: { ERR_UNKNOWN_BUILTIN_MODULE } } = require('internal/errors');
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const { getCodePath, isSea } = internalBinding('sea');
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// This is roughly the same as:
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//
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// const mod = new Module(filename);
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// mod._compile(contents, filename);
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//
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// but the code has been duplicated because currently there is no way to set the
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// value of require.main to module.
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//
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// TODO(RaisinTen): Find a way to deduplicate this.
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function embedderRunCjs(contents) {
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const filename = process.execPath;
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const { function: compiledWrapper } = wrapSafe(
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isSea() ? getCodePath() : filename,
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contents);
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const customModule = new Module(filename, null);
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customModule.filename = filename;
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customModule.paths = Module._nodeModulePaths(customModule.path);
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const customExports = customModule.exports;
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embedderRequire.main = customModule;
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const customFilename = customModule.filename;
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const customDirname = customModule.path;
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return compiledWrapper(
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customExports,
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embedderRequire,
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customModule,
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customFilename,
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customDirname);
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}
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function embedderRequire(id) {
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const normalizedId = normalizeRequirableId(id);
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if (!normalizedId) {
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throw new ERR_UNKNOWN_BUILTIN_MODULE(id);
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}
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return require(normalizedId);
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}
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module.exports = { embedderRequire, embedderRunCjs };
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