esm: fallback to getSource when load returns nullish source

When using the Modules Customization Hooks API to load CommonJS modules, we want to support the returned value of `defaultLoad` which must be nullish to preserve backward compatibility. This can be achieved by fetching the source from the translator. PR-URL: #50825Fixes: #50435 Reviewed-By: Geoffrey Booth <[email protected]> Reviewed-By: Jacob Smith <[email protected]>

Author: aduh95

lib/internal/modules/esm/load.js

@@ -262,5 +262,6 @@ function throwUnknownModuleFormat(url, format){
 module.exports={
  defaultLoad,
  defaultLoadSync,
+ getSourceSync,
  throwUnknownModuleFormat,
 };

lib/internal/modules/esm/translators.js

@@ -31,6 +31,7 @@ function lazyTypes(){
 }
 
 const{ containsModuleSyntax }=internalBinding('contextify');
+const{ BuiltinModule }=require('internal/bootstrap/realm');
 constassert=require('internal/assert');
 const{ readFileSync }=require('fs');
 const{ dirname, extname, isAbsolute }=require('path');
@@ -58,6 +59,17 @@ const asyncESM = require('internal/process/esm_loader');
 const{ emitWarningSync }=require('internal/process/warning');
 const{ internalCompileFunction }=require('internal/vm');
 
+// Lazy-loading to avoid circular dependencies.
+letgetSourceSync;
+/**
+ * @param{Parameters<typeof import('./load').getSourceSync>[0]} url
+ * @returns{ReturnType<typeof import('./load').getSourceSync>}
+ */
+functiongetSource(url){
+getSourceSync??=require('internal/modules/esm/load').getSourceSync;
+returngetSourceSync(url);
+}
+
 /** @type{import('deps/cjs-module-lexer/lexer.js').parse} */
 letcjsParse;
 /**
@@ -225,21 +237,19 @@ function loadCJSModule(module, source, url, filename){
 // eslint-disable-next-line func-name-matching,func-style
 constrequireFn=functionrequire(specifier){
 letimportAttributes=kEmptyObject;
-if(!StringPrototypeStartsWith(specifier,'node:')){
+if(!StringPrototypeStartsWith(specifier,'node:')&&!BuiltinModule.normalizeRequirableId(specifier)){
 // TODO: do not depend on the monkey-patchable CJS loader here.
 constpath=CJSModule._resolveFilename(specifier,module);
-if(specifier!==path){
-switch(extname(path)){
-case'.json':
-importAttributes={__proto__: null,type: 'json'};
-break;
-case'.node':
-returnCJSModule._load(specifier,module);
-default:
+switch(extname(path)){
+case'.json':
+importAttributes={__proto__: null,type: 'json'};
+break;
+case'.node':
+returnCJSModule._load(specifier,module);
+default:
 // fall through
-}
-specifier=`${pathToFileURL(path)}`;
 }
+specifier=`${pathToFileURL(path)}`;
 }
 constjob=asyncESM.esmLoader.getModuleJobSync(specifier,url,importAttributes);
 job.runSync();
@@ -276,7 +286,8 @@ function createCJSModuleWrap(url, source, isMain, loadCJS = loadCJSModule){
 debug(`Translating CJSModule ${url}`);
 
 constfilename=StringPrototypeStartsWith(url,'file://') ? fileURLToPath(url) : url;
-source=stringify(source);
+// In case the source was not provided by the `load` step, we need fetch it now.
+source=stringify(source??getSource(newURL(url)).source);
 
 const{ exportNames, module }=cjsPreparseModuleExports(filename,source);
 cjsCache.set(url,module);

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

@@ -736,4 +736,39 @@ describe('Loader hooks',{concurrency: true }, () =>{
 assert.strictEqual(code,0);
 assert.strictEqual(signal,null);
 });
+
+it('should handle mixed of opt-in modules and non-opt-in ones',async()=>{
+const{ code, signal, stdout, stderr }=awaitspawnPromisified(execPath,[
+'--no-warnings',
+'--experimental-loader',
+`data:text/javascript,const fixtures=${JSON.stringify(fixtures.path('empty.js'))};export ${
+encodeURIComponent(functionresolve(s,c,n){
+if(s.endsWith('entry-point')){
+return{
+shortCircuit: true,
+url: 'file:///c:/virtual-entry-point',
+format: 'commonjs',
+};
+}
+returnn(s,c);
+})
+}export ${
+encodeURIComponent(asyncfunctionload(u,c,n){
+if(u==='file:///c:/virtual-entry-point'){
+return{
+shortCircuit: true,
+source: `"use strict"require(${JSON.stringify(fixtures)});console.log("Hello");`,
+format: 'commonjs',
+};
+}
+returnn(u,c);
+})}`,
+'entry-point',
+]);
+
+assert.strictEqual(stderr,'');
+assert.strictEqual(stdout,'Hello\n');
+assert.strictEqual(code,0);
+assert.strictEqual(signal,null);
+});
 });