[ESM] always load the ESM loader (#279)

* [ESM] always load the ESM loader

* Enable esmodule tests on Windows

* Suppress ExperimentalWarning messages

Author: kherock

lib/get-source-loader.mjs

@@ -1,6 +1,6 @@
 const vm = require('vm');
 
-module.exports = (patchVM, wrapper, callback) => {
+module.exports = (patchVM, callback) => {
   // Hook into Node's `require(...)`
   updateHooks();
 
@@ -48,12 +48,6 @@ module.exports = (patchVM, wrapper, callback) => {
    */
   function createHook(handler) {
     return function nodeDevHook(module, filename) {
-      if (module.parent === wrapper) {
-        // If the main module is required conceal the wrapper
-        module.id = '.';
-        module.parent = null;
-        process.mainModule = module;
-      }
       if (!module.loaded) callback(module.filename);
 
       // Invoke the original handler

lib/hook.js

@@ -1,8 +1,7 @@
 const { fork } = require('child_process');
 const filewatcher = require('filewatcher');
-const { extname } = require('path');
 const semver = require('semver');
-const getPackageType = require('get-package-type');
+const { pathToFileURL } = require('url');
 
 const { clearFactory } = require('./clear');
 const { configureDeps, configureIgnore } = require('./ignore');
@@ -55,8 +54,6 @@ module.exports = function (
   const isIgnored = configureIgnore(ignore);
   const isTooDeep = configureDeps(deps);
 
-  const wrapper = resolveMain(localPath('wrap.js'));
-
   // Run ./dedupe.js as preload script
   if (dedupe) process.env.NODE_DEV_PRELOAD = localPath('dedupe');
 
@@ -96,27 +93,24 @@ module.exports = function (
 
     const args = nodeArgs.slice();
 
-    if (extname(script) === '.mjs' || getPackageType.sync(script) === 'module') {
-      if (semver.satisfies(process.version, '>=10 <12.11.1')) {
-        const resolveLoader = resolveMain(localPath('resolve-loader.mjs'));
-        args.push('--experimental-modules', `--loader=${resolveLoader}`);
-      } else if (semver.satisfies(process.version, '>=12.11.1')) {
-        if (semver.satisfies(process.version, '<12.17.0')) {
-          args.push('--experimental-modules');
-        }
-        const loaderPath = semver.satisfies(process.version, '>=16.12.0')
-          ? 'load-loader.mjs'
-          : 'get-source-loader.mjs';
-        const experimentalLoader = resolveMain(localPath(loaderPath));
-        args.push(`--experimental-loader=${experimentalLoader}`);
-      }
+    args.push(`--require=${resolveMain(localPath('wrap'))}`);
+    const loaderPath = semver.satisfies(process.version, '<16.12.0')
+      ? 'loader-legacy.mjs'
+      : 'loader.mjs';
+    const loader = pathToFileURL(resolveMain(localPath(loaderPath)));
+    if (semver.satisfies(process.version, '<12.17.0')) {
+      args.push('--experimental-modules');
+    }
+    if (semver.satisfies(process.version, '<12.11.1')) {
+      args.push(`--loader=${loader.href}`);
+    } else {
+      args.push(`--experimental-loader=${loader.href}`);
     }
 
-    const cmd = args.concat(wrapper, script, scriptArgs);
-
-    child = fork(cmd[0], cmd.slice(1), {
+    child = fork(script, scriptArgs, {
       cwd: process.cwd(),
-      env: process.env
+      env: process.env,
+      execArgv: args
     });
 
     if (respawn) {

lib/index.js

@@ -0,0 +1,20 @@
+import { createRequire } from 'module';
+import { fileURLToPath } from 'url';
+import { send } from './ipc.mjs';
+
+const require = createRequire(import.meta.url);
+
+export async function getFormat(url, context, defaultGetFormat) {
+  const getPackageType = require('get-package-type');
+  const filePath = fileURLToPath(url);
+
+  send({ required: filePath });
+  try {
+    return await defaultGetFormat(url, context, defaultGetFormat);
+  } catch (err) {
+    if (err.code === 'ERR_UNKNOWN_FILE_EXTENSION') {
+      return { format: await getPackageType(filePath) };
+    }
+    throw err;
+  }
+}

lib/load-loader.mjs

@@ -0,0 +1,20 @@
+import { createRequire } from 'module';
+import { fileURLToPath } from 'url';
+import { send } from './ipc.mjs';
+
+const require = createRequire(import.meta.url);
+
+export async function load(url, context, defaultLoad) {
+  const getPackageType = require('get-package-type');
+  const filePath = fileURLToPath(url);
+
+  send({ required: filePath });
+  try {
+    return await defaultLoad(url, context, defaultLoad);
+  } catch (err) {
+    if (err.code === 'ERR_UNKNOWN_FILE_EXTENSION') {
+      return { format: await getPackageType(filePath), source: null };
+    }
+    throw err;
+  }
+}

lib/loader-legacy.mjs

@@ -0,0 +1,13 @@
+const { emitWarning } = process;
+
+process.emitWarning = (warning, ...args) => {
+  if (args[0] === 'ExperimentalWarning') {
+    return;
+  }
+
+  if (args[0] && typeof args[0] === 'object' && args[0].type === 'ExperimentalWarning') {
+    return;
+  }
+
+  return emitWarning(warning, ...args);
+};

lib/loader.mjs

@@ -1,22 +1,19 @@
 const { dirname, extname } = require('path');
 const childProcess = require('child_process');
 const { sync: resolve } = require('resolve');
-const getPackageType = require('get-package-type');
 
 const { getConfig } = require('./cfg');
 const hook = require('./hook');
 const { relay, send } = require('./ipc');
 const resolveMain = require('./resolve-main');
 
-// Remove wrap.js from the argv array
-process.argv.splice(1, 1);
-
 const script = process.argv[1];
 const { extensions, fork, vm } = getConfig(script);
 
 if (process.env.NODE_DEV_PRELOAD) {
   require(process.env.NODE_DEV_PRELOAD);
 }
+require('./suppress-experimental');
 
 // We want to exit on SIGTERM, but defer to existing SIGTERM handlers.
 process.once('SIGTERM', () => process.listenerCount('SIGTERM') || process.exit(0));
@@ -26,7 +23,7 @@ if (fork) {
   // too. We also need to relay messages about required files to the parent.
   const originalFork = childProcess.fork;
   childProcess.fork = (modulePath, args, options) => {
-    const child = originalFork(__filename, [modulePath].concat(args), options);
+    const child = originalFork(modulePath, args, options);
     relay(child);
     return child;
   };
@@ -48,7 +45,7 @@ process.on('uncaughtException', err => {
 });
 
 // Hook into require() and notify the parent process about required files
-hook(vm, module, required => send({ required }));
+hook(vm, required => send({ required }));
 
 // Check if a module is registered for this extension
 const main = resolveMain(script);
@@ -66,6 +63,3 @@ if (typeof mod === 'object' && mod.name) {
 } else if (typeof mod === 'string') {
   require(resolve(mod, { basedir }));
 }
-
-// Execute the wrapped script
-ext === 'mjs' || getPackageType.sync(main) === 'module' ? import(main) : require(main);

lib/resolve-loader.mjs

@@ -6,7 +6,7 @@ tap.test('should not show up in argv', t => {
   spawn('argv.js foo', out => {
     const argv = JSON.parse(out.replace(/'/g, '"'));
     t.match(argv[0], /.*?node(js|\.exe)?$/);
-    t.equal(argv[1], 'argv.js');
+    t.match(argv[1], /.*[\\/]argv\.js$/);
     t.equal(argv[2], 'foo');
     return { exit: t.end.bind(t) };
   });