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shouldLoadAsEsm.ts
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shouldLoadAsEsm.ts
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/**
* Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
import {dirname, extname} from 'path';
// @ts-ignore: experimental, not added to the types
import {SyntheticModule} from 'vm';
import type {Config} from '@jest/types';
import readPkgUp = require('read-pkg-up');
const runtimeSupportsVmModules = typeof SyntheticModule === 'function';
const cachedFileLookups = new Map<string, boolean>();
const cachedDirLookups = new Map<string, boolean>();
export function clearCachedLookups(): void {
cachedFileLookups.clear();
cachedDirLookups.clear();
}
export default function cachedShouldLoadAsEsm(path: Config.Path): boolean {
let cachedLookup = cachedFileLookups.get(path);
if (cachedLookup === undefined) {
cachedLookup = shouldLoadAsEsm(path);
cachedFileLookups.set(path, cachedLookup);
}
return cachedLookup;
}
// this is a bad version of what https://github.com/nodejs/modules/issues/393 would provide
function shouldLoadAsEsm(path: Config.Path): boolean {
if (!runtimeSupportsVmModules) {
return false;
}
const extension = extname(path);
if (extension === '.mjs') {
return true;
}
if (extension === '.cjs') {
return false;
}
// this isn't correct - we might wanna load any file as a module (using synthetic module)
// do we need an option to Jest so people can opt in to ESM for non-js?
if (extension !== '.js') {
return false;
}
const cwd = dirname(path);
let cachedLookup = cachedDirLookups.get(cwd);
if (cachedLookup === undefined) {
cachedLookup = cachedPkgCheck(cwd);
cachedFileLookups.set(cwd, cachedLookup);
}
return cachedLookup;
}
function cachedPkgCheck(cwd: Config.Path): boolean {
// TODO: can we cache lookups somehow?
const pkg = readPkgUp.sync({cwd, normalize: false});
if (!pkg) {
return false;
}
return pkg.packageJson.type === 'module';
}