node/lib/internal/modules/run_main.js
Jacob Smith d859e9e997
esm: add chaining to loaders
PR-URL: https://github.com/nodejs/node/pull/42623
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
2022-05-04 16:51:12 +01:00

89 lines
2.6 KiB
JavaScript

'use strict';
const {
ObjectCreate,
StringPrototypeEndsWith,
} = primordials;
const CJSLoader = require('internal/modules/cjs/loader');
const { Module, toRealPath, readPackageScope } = CJSLoader;
const { getOptionValue } = require('internal/options');
const path = require('path');
const {
handleProcessExit,
} = require('internal/modules/esm/handle_process_exit');
function resolveMainPath(main) {
// Note extension resolution for the main entry point can be deprecated in a
// future major.
// Module._findPath is monkey-patchable here.
let mainPath = Module._findPath(path.resolve(main), null, true);
if (!mainPath)
return;
const preserveSymlinksMain = getOptionValue('--preserve-symlinks-main');
if (!preserveSymlinksMain)
mainPath = toRealPath(mainPath);
return mainPath;
}
function shouldUseESMLoader(mainPath) {
/**
* @type {string[]} userLoaders A list of custom loaders registered by the user
* (or an empty list when none have been registered).
*/
const userLoaders = getOptionValue('--experimental-loader');
if (userLoaders.length > 0)
return true;
const esModuleSpecifierResolution =
getOptionValue('--experimental-specifier-resolution');
if (esModuleSpecifierResolution === 'node')
return true;
// Determine the module format of the main
if (mainPath && StringPrototypeEndsWith(mainPath, '.mjs'))
return true;
if (!mainPath || StringPrototypeEndsWith(mainPath, '.cjs'))
return false;
const pkg = readPackageScope(mainPath);
return pkg && pkg.data.type === 'module';
}
function runMainESM(mainPath) {
const { loadESM } = require('internal/process/esm_loader');
const { pathToFileURL } = require('internal/url');
handleMainPromise(loadESM((esmLoader) => {
const main = path.isAbsolute(mainPath) ?
pathToFileURL(mainPath).href : mainPath;
return esmLoader.import(main, undefined, ObjectCreate(null));
}));
}
async function handleMainPromise(promise) {
process.on('exit', handleProcessExit);
try {
return await promise;
} finally {
process.off('exit', handleProcessExit);
}
}
// For backwards compatibility, we have to run a bunch of
// monkey-patchable code that belongs to the CJS loader (exposed by
// `require('module')`) even when the entry point is ESM.
function executeUserEntryPoint(main = process.argv[1]) {
const resolvedMain = resolveMainPath(main);
const useESMLoader = shouldUseESMLoader(resolvedMain);
if (useESMLoader) {
runMainESM(resolvedMain || main);
} else {
// Module._load is the monkey-patchable CJS module loader.
Module._load(main, null, true);
}
}
module.exports = {
executeUserEntryPoint,
handleMainPromise,
};