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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>
Node.js Core Tests
This directory contains code and data used to test the Node.js implementation.
For a detailed guide on how to write tests in this directory, see the guide on writing tests.
On how to run tests in this directory, see the contributing guide.
For the tests to run on Windows, be sure to clone Node.js source code with the
autocrlf git config flag set to true.
Test Directories
| Directory | Runs on CI | Purpose |
|---|---|---|
abort |
Yes | Tests that use --abort-on-uncaught-exception and other situations where we want to test something but avoid generating a core file. |
addons |
Yes | Tests for addon functionality along with some tests that require an addon. |
async-hooks |
Yes | Tests for async_hooks functionality. |
benchmark |
Yes | Test minimal functionality of benchmarks. |
cctest |
Yes | C++ tests that are run as part of the build process. |
code-cache |
No | Tests for a Node.js binary compiled with V8 code cache. |
common |
Common modules shared among many tests. Documentation | |
doctool |
Yes | Tests for the documentation generator. |
es-module |
Yes | Test ESM module loading. |
fixtures |
Test fixtures used in various tests throughout the test suite. | |
internet |
No | Tests that make real outbound network connections. Tests for networking related modules may also be present in other directories, but those tests do not make outbound connections. |
js-native-api |
Yes | Tests for Node.js-agnostic Node-API functionality. |
known_issues |
Yes | Tests reproducing known issues within the system. All tests inside of this directory are expected to fail. If a test doesn't fail on certain platforms, those should be skipped via known_issues.status. |
message |
Yes | Tests for messages that are output for various conditions (console.log, error messages etc.) |
node-api |
Yes | Tests for Node.js-specific Node-API functionality. |
parallel |
Yes | Various tests that are able to be run in parallel. |
pseudo-tty |
Yes | Tests that require stdin/stdout/stderr to be a TTY. |
pummel |
No | Various tests for various modules / system functionality operating under load. |
sequential |
Yes | Various tests that must not run in parallel. |
testpy |
Test configuration utility used by various test suites. | |
tick-processor |
No | Tests for the V8 tick processor integration. The tests are for the logic in lib/internal/v8_prof_processor.js and lib/internal/v8_prof_polyfill.js. The tests confirm that the profile processor packages the correct set of scripts from V8 and introduces the correct platform specific logic. |
v8-updates |
No | Tests for V8 performance integration. |