module: fix hook module CJS dependency loading

It can be useful to load dependencies as part of the loader hook
definition file. This fixes a bug where `import x from 'x'` would
always return `x` as `undefined` if the import was made in a loader
hooks definition module.

A parallel change to the CJS loading injection process meant that the
CJS module wasn't being injected into the correct loader instance,
which is corrected here with a test.

PR-URL: nodejs/node#16381
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

Author: guybedford

lib/module.js

@@ -431,7 +431,8 @@ Module._load = function(request, parent, isMain) {
         ESMLoader = new Loader();
         const userLoader = process.binding('config').userLoader;
         if (userLoader) {
-          const hooks = await new Loader().import(userLoader);
+          const hooks = await ESMLoader.import(userLoader);
+          ESMLoader = new Loader();
           ESMLoader.hook(hooks);
         }
       }

test/es-module/test-esm-loader-dependency.mjs

@@ -0,0 +1,5 @@
+// Flags: --experimental-modules --loader ./test/fixtures/es-module-loaders/loader-with-dep.mjs
+/* eslint-disable required-modules */
+import './test-esm-ok.mjs';
+
+// We just test that this module doesn't fail loading

test/fixtures/es-module-loaders/loader-dep.js

@@ -0,0 +1 @@
+exports.format = 'esm';

test/fixtures/es-module-loaders/loader-with-dep.mjs

@@ -0,0 +1,7 @@
+import dep from './loader-dep.js';
+export function resolve (specifier, base, defaultResolve) {
+  return {
+    url: defaultResolve(specifier, base).url,
+    format: dep.format
+  };
+}