esm: bypass CJS loader in default load under --default-type=module

This allows user to opt-out from using the monkey-patchable CJS loader, even to load CJS modules. PR-URL: #50004 Reviewed-By: Geoffrey Booth <[email protected]>

Author: aduh95

doc/api/module.md

@@ -622,7 +622,8 @@ Omitting vs providing a `source` for `'commonjs'` has very different effects:
  registered hooks. This behavior for nullish `source` is temporary — in the
  future, nullish `source` will not be supported.
 
-The Node.js internal `load` implementation, which is the value of `next` for the
+When `node` is run with `--experimental-default-type=commonjs`, the Node.js
+internal `load` implementation, which is the value of `next` for the
 last hook in the `load` chain, returns `null` for `source` when `format` is
 `'commonjs'` for backward compatibility. Here is an example hook that would
 opt-in to using the non-default behavior:

lib/internal/modules/esm/load.js

@@ -18,6 +18,8 @@ const policy = getOptionValue('--experimental-policy') ?
 null;
 constexperimentalNetworkImports=
 getOptionValue('--experimental-network-imports');
+constdefaultType=
+getOptionValue('--experimental-default-type');
 
 const{Buffer: {from: BufferFrom}}=require('buffer');
 
@@ -140,7 +142,7 @@ async function defaultLoad(url, context = kEmptyObject){
 // Now that we have the source for the module, run `defaultGetFormat` again in case we detect ESM syntax.
 format??=awaitdefaultGetFormat(urlInstance,contextToPass);
 
-if(format==='commonjs'&&contextToPass!==context){
+if(format==='commonjs'&&contextToPass!==context&&defaultType!=='module'){
 // For backward compatibility reasons, we need to discard the source in
 // order for the CJS loader to re-fetch it.
 source=null;

test/es-module/test-esm-type-flag-errors.mjs

@@ -1,31 +1,101 @@
 import{spawnPromisified}from'../common/index.mjs';
 import*asfixturesfrom'../common/fixtures.mjs';
 import{describe,it}from'node:test';
-import{match,strictEqual}from'node:assert';
-
-describe('--experimental-default-type=module should not affect the interpretation of files with unknown extensions',
-{concurrency: true},()=>{
-it('should error on an entry point with an unknown extension',async()=>{
-const{ code, signal, stdout, stderr }=awaitspawnPromisified(process.execPath,[
-'--experimental-default-type=module',
-fixtures.path('es-modules/package-type-module/extension.unknown'),
-]);
-
-match(stderr,/ERR_UNKNOWN_FILE_EXTENSION/);
-strictEqual(stdout,'');
-strictEqual(code,1);
-strictEqual(signal,null);
-});
-
-it('should error on an import with an unknown extension',async()=>{
-const{ code, signal, stdout, stderr }=awaitspawnPromisified(process.execPath,[
-'--experimental-default-type=module',
-fixtures.path('es-modules/package-type-module/imports-unknownext.mjs'),
-]);
-
-match(stderr,/ERR_UNKNOWN_FILE_EXTENSION/);
-strictEqual(stdout,'');
-strictEqual(code,1);
-strictEqual(signal,null);
-});
-});
+import{deepStrictEqual,match,strictEqual}from'node:assert';
+
+describe('--experimental-default-type=module',{concurrency: true},()=>{
+describe('should not affect the interpretation of files with unknown extensions',{concurrency: true},()=>{
+it('should error on an entry point with an unknown extension',async()=>{
+const{ code, signal, stdout, stderr }=awaitspawnPromisified(process.execPath,[
+'--experimental-default-type=module',
+fixtures.path('es-modules/package-type-module/extension.unknown'),
+]);
+
+match(stderr,/ERR_UNKNOWN_FILE_EXTENSION/);
+strictEqual(stdout,'');
+strictEqual(code,1);
+strictEqual(signal,null);
+});
+
+it('should error on an import with an unknown extension',async()=>{
+const{ code, signal, stdout, stderr }=awaitspawnPromisified(process.execPath,[
+'--experimental-default-type=module',
+fixtures.path('es-modules/package-type-module/imports-unknownext.mjs'),
+]);
+
+match(stderr,/ERR_UNKNOWN_FILE_EXTENSION/);
+strictEqual(stdout,'');
+strictEqual(code,1);
+strictEqual(signal,null);
+});
+});
+
+it('should affect CJS .js files (imported, required, entry points)',async()=>{
+constresult=awaitspawnPromisified(process.execPath,[
+'--experimental-default-type=module',
+fixtures.path('es-modules/package-type-commonjs/echo-require-cache.js'),
+]);
+
+deepStrictEqual(result,{
+code: 0,
+stderr: '',
+stdout: 'undefined\n',
+signal: null,
+});
+});
+
+it('should affect .cjs files that are imported',async()=>{
+constresult=awaitspawnPromisified(process.execPath,[
+'--experimental-default-type=module',
+'-e',
+`import ${JSON.stringify(fixtures.fileURL('es-module-require-cache/echo.cjs'))}`,
+]);
+
+deepStrictEqual(result,{
+code: 0,
+stderr: '',
+stdout: 'undefined\n',
+signal: null,
+});
+});
+
+it('should affect entry point .cjs files (with no hooks)',async()=>{
+const{ stderr, stdout, code }=awaitspawnPromisified(process.execPath,[
+'--experimental-default-type=module',
+fixtures.path('es-module-require-cache/echo.cjs'),
+]);
+
+strictEqual(stderr,'');
+match(stdout,/^undefined\n$/);
+strictEqual(code,0);
+});
+
+it('should affect entry point .cjs files (when any hooks is registered)',async()=>{
+constresult=awaitspawnPromisified(process.execPath,[
+'--experimental-default-type=module',
+'--import',
+'data:text/javascript,import{register}from"node:module"register("data:text/javascript,");',
+fixtures.path('es-module-require-cache/echo.cjs'),
+]);
+
+deepStrictEqual(result,{
+code: 0,
+stderr: '',
+stdout: 'undefined\n',
+signal: null,
+});
+});
+
+it('should not affect CJS from input-type',async()=>{
+const{ stderr, stdout, code }=awaitspawnPromisified(process.execPath,[
+'--experimental-default-type=module',
+'--input-type=commonjs',
+'-p',
+'require.cache',
+]);
+
+strictEqual(stderr,'');
+match(stdout,/^\[Object:nullprototype\]\{\}\n$/);
+strictEqual(code,0);
+});
+});

test/fixtures/es-module-require-cache/echo.cjs

@@ -0,0 +1 @@
+console.log(require.cache);

test/fixtures/es-modules/package-type-commonjs/echo-require-cache.js

@@ -0,0 +1 @@
+console.log(require.cache);