module: warn on detection in typeless package

PR-URL: #52168
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Vinícius Lourenço Claro Cardoso <contact@viniciusl.com.br>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

Author: GeoffreyBooth

lib/internal/modules/esm/get_format.js

@@ -5,6 +5,7 @@ const {
  ObjectPrototypeHasOwnProperty,
  PromisePrototypeThen,
  PromiseResolve,
+ SafeSet,
  StringPrototypeIncludes,
  StringPrototypeCharCodeAt,
  StringPrototypeSlice,
@@ -19,7 +20,7 @@ const {
 constexperimentalNetworkImports=
 getOptionValue('--experimental-network-imports');
 const{ containsModuleSyntax }=internalBinding('contextify');
-const{ getPackageType }=require('internal/modules/esm/resolve');
+const{getPackageScopeConfig,getPackageType }=require('internal/modules/esm/resolve');
 const{ fileURLToPath }=require('internal/url');
 const{ERR_UNKNOWN_FILE_EXTENSION}=require('internal/errors').codes;
 
@@ -81,6 +82,7 @@ function underNodeModules(url) {
 returnStringPrototypeIncludes(url.pathname,'/node_modules/');
 }
 
+lettypelessPackageJsonFilesWarnedAbout;
 /**
  * @param {URL} url
  * @param {{parentURL: string; source?: Buffer}} context
@@ -92,7 +94,7 @@ function getFileProtocolModuleFormat(url, context = { __proto__: null }, ignoreE
 constext=extname(url);
 
 if(ext==='.js'){
-constpackageType=getPackageType(url);
+const{type: packageType, pjsonPath }=getPackageScopeConfig(url);
 if(packageType!=='none'){
 returnpackageType;
 }
@@ -111,9 +113,23 @@ function getFileProtocolModuleFormat(url, context = { __proto__: null }, ignoreE
 // `source` is undefined when this is called from `defaultResolve`;
 // but this gets called again from `defaultLoad`/`defaultLoadSync`.
 if(getOptionValue('--experimental-detect-module')){
-returnsource ?
+constformat=source ?
 (containsModuleSyntax(`${source}`,fileURLToPath(url)) ? 'module' : 'commonjs') :
 null;
+if(format==='module'){
+// This module has a .js extension, a package.json with no `type` field, and ESM syntax.
+// Warn about the missing `type` field so that the user can avoid the performance penalty of detection.
+typelessPackageJsonFilesWarnedAbout??=newSafeSet();
+if(!typelessPackageJsonFilesWarnedAbout.has(pjsonPath)){
+constwarning=`${url} parsed as an ES module because module syntax was detected;`+
+` to avoid the performance penalty of syntax detection, add "type": "module" to ${pjsonPath}`;
+process.emitWarning(warning,{
+code: 'MODULE_TYPELESS_PACKAGE_JSON',
+});
+typelessPackageJsonFilesWarnedAbout.add(pjsonPath);
+}
+}
+returnformat;
 }
 return'commonjs';
 }

test/es-module/test-esm-detect-ambiguous.mjs

@@ -101,6 +101,7 @@ describe('--experimental-detect-module', { concurrency: true }, () => {
 ]){
 it(testName,async()=>{
 const{ stdout, stderr, code, signal }=awaitspawnPromisified(process.execPath,[
+'--no-warnings',
 '--experimental-detect-module',
 entryPath,
 ]);
@@ -142,6 +143,7 @@ describe('--experimental-detect-module', { concurrency: true }, () => {
 ]){
 it(testName,async()=>{
 const{ stdout, stderr, code, signal }=awaitspawnPromisified(process.execPath,[
+'--no-warnings',
 '--experimental-detect-module',
 entryPath,
 ]);
@@ -291,6 +293,7 @@ describe('--experimental-detect-module', { concurrency: true }, () => {
 
 it('permits declaration of CommonJS module variables',async()=>{
 const{ stdout, stderr, code, signal }=awaitspawnPromisified(process.execPath,[
+'--no-warnings',
 '--experimental-detect-module',
 fixtures.path('es-modules/package-without-type/commonjs-wrapper-variables.js'),
 ]);
@@ -327,6 +330,48 @@ describe('--experimental-detect-module', { concurrency: true }, () => {
 strictEqual(signal,null);
 });
 });
+
+describe('warn about typeless packages for .js files with ESM syntax',{concurrency: true},()=>{
+for(const{ testName, entryPath }of[
+{
+testName: 'warns for ESM syntax in a .js entry point in a typeless package',
+entryPath: fixtures.path('es-modules/package-without-type/module.js'),
+},
+{
+testName: 'warns for ESM syntax in a .js file imported by a CommonJS entry point in a typeless package',
+entryPath: fixtures.path('es-modules/package-without-type/imports-esm.js'),
+},
+{
+testName: 'warns for ESM syntax in a .js file imported by an ESM entry point in a typeless package',
+entryPath: fixtures.path('es-modules/package-without-type/imports-esm.mjs'),
+},
+]){
+it(testName,async()=>{
+const{ stdout, stderr, code, signal }=awaitspawnPromisified(process.execPath,[
+'--experimental-detect-module',
+entryPath,
+]);
+
+match(stderr,/MODULE_TYPELESS_PACKAGE_JSON/);
+strictEqual(stdout,'executed\n');
+strictEqual(code,0);
+strictEqual(signal,null);
+});
+}
+
+it('warns only once for a package.json that affects multiple files',async()=>{
+const{ stdout, stderr, code, signal }=awaitspawnPromisified(process.execPath,[
+'--experimental-detect-module',
+fixtures.path('es-modules/package-without-type/detected-as-esm.js'),
+]);
+
+match(stderr,/MODULE_TYPELESS_PACKAGE_JSON/);
+strictEqual(stderr.match(/MODULE_TYPELESS_PACKAGE_JSON/g).length,1);
+strictEqual(stdout,'executed\nexecuted\n');
+strictEqual(code,0);
+strictEqual(signal,null);
+});
+});
 });
 
 // Validate temporarily disabling `--abort-on-uncaught-exception`

test/fixtures/es-modules/package-without-type/detected-as-esm.js

@@ -0,0 +1,2 @@
+import'./module.js';
+console.log('executed');