nodejs · juanarbol · Nov 28, 2019 · Nov 28, 2019 · Nov 28, 2019 · Dec 3, 2019
diff --git a/lib/internal/errors.js b/lib/internal/errors.js
@@ -90,6 +90,13 @@ function lazyBuffer() {
   return buffer;
 }
 
+let pathModule;
+function lazyPath() {
+  if (pathModule === undefined)
+    pathModule = require('path');
+  return pathModule;
+}
+
 // A specialized Error that includes an additional info property with
 // additional information about the error condition.
 // It has the properties present in a UVException but with a custom error
@@ -1122,7 +1129,26 @@ E('ERR_OUT_OF_RANGE',
     msg += ` It must be ${range}. Received ${received}`;
     return msg;
   }, RangeError);
-E('ERR_REQUIRE_ESM', 'Must use import to load ES Module: %s', Error);
+E('ERR_REQUIRE_ESM', (filename, module = null, pkg = null) => {
+  let msg = `Must use import to load ES Module: ${filename}\n`;
+  if (module && pkg) {
+    const parentPath = module.parent && module.parent.filename;
+    const basename = parentPath &&
+        lazyPath().basename(filename) === lazyPath().basename(parentPath) ?
+      filename : lazyPath().basename(filename);
+    msg +=
+      'require() of ES modules is not supported.\nrequire() of ' +
+      `${filename} ${parentPath ? `from ${module.parent.filename} ` : ''}` +
+      'is an ES module file as it is a .js file whose nearest parent ' +
+      'package.json contains "type": "module" which defines all .js ' +
+      'files in that package scope as ES modules.\nInstead rename ' +
+      `${basename} to end in .cjs, change the requiring code to use ` +
+      'import(), or remove "type": "module" from ' +
+      `${lazyPath().resolve(pkg.path, 'package.json')}.\n`;
+    return msg;
+  }
+  return msg;
+}, Error);
 E('ERR_SCRIPT_EXECUTION_INTERRUPTED',
   'Script execution was interrupted by `SIGINT`', Error);
 E('ERR_SERVER_ALREADY_LISTEN',

diff --git a/lib/internal/modules/cjs/loader.js b/lib/internal/modules/cjs/loader.js
@@ -1191,33 +1191,12 @@ Module.prototype._compile = function(content, filename) {
 };
 
 // Native extension for .js
-let warnRequireESM = true;
 Module._extensions['.js'] = function(module, filename) {
   if (filename.endsWith('.js')) {
     const pkg = readPackageScope(filename);
+    // Function require shouldn't be used in ES modules.
     if (pkg && pkg.data && pkg.data.type === 'module') {
-      if (warnRequireESM) {
-        const parentPath = module.parent && module.parent.filename;
-        const basename = parentPath &&
-            path.basename(filename) === path.basename(parentPath) ?
-          filename : path.basename(filename);
-        process.emitWarning(
-          'require() of ES modules is not supported.\nrequire() of ' +
-          `${filename} ${parentPath ? `from ${module.parent.filename} ` : ''}` +
-          'is an ES module file as it is a .js file whose nearest parent ' +
-          'package.json contains "type": "module" which defines all .js ' +
-          'files in that package scope as ES modules.\nInstead rename ' +
-          `${basename} to end in .cjs, change the requiring code to use ` +
-          'import(), or remove "type": "module" from ' +
-          `${path.resolve(pkg.path, 'package.json')}.`,
-          undefined,
-          undefined,
-          undefined,
-          true
-        );
-        warnRequireESM = false;
-      }
-      throw new ERR_REQUIRE_ESM(filename);
+      throw new ERR_REQUIRE_ESM(filename, module, pkg);
     }
   }
   const content = fs.readFileSync(filename, 'utf8');

diff --git a/test/es-module/test-cjs-esm-warn.js b/test/es-module/test-cjs-esm-warn.js
@@ -26,15 +26,19 @@ child.on('close', common.mustCall((code, signal) => {
   assert.strictEqual(code, 1);
   assert.strictEqual(signal, null);
 
-  assert.ok(stderr.startsWith(`(node:${child.pid}) Warning: ` +
-    'require() of ES modules is not supported.\nrequire() of ' +
+  assert.ok(stderr.indexOf(
+    `Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: ${required}` +
+    '\nrequire() of ES modules is not supported.\nrequire() of ' +
     `${required} from ${requiring} ` +
     'is an ES module file as it is a .js file whose nearest parent ' +
     'package.json contains "type": "module" which defines all .js ' +
     'files in that package scope as ES modules.\nInstead rename ' +
     `${basename} to end in .cjs, change the requiring code to use ` +
     'import(), or remove "type": "module" from ' +
-    `${pjson}.\n`));
+    `${pjson}.\n`) !== -1);
   assert.ok(stderr.indexOf(
     'Error [ERR_REQUIRE_ESM]: Must use import to load ES Module') !== -1);
+
+  assert.strictEqual(
+    stderr.match(/Must use import to load ES Module/g).length, 1);
 }));
diff --git a/test/es-module/test-esm-type-flag-errors.js b/test/es-module/test-esm-type-flag-errors.js
@@ -27,7 +27,10 @@ try {
   require('../fixtures/es-modules/package-type-module/index.js');
   assert.fail('Expected CJS to fail loading from type: module package.');
 } catch (e) {
-  assert(e.toString().match(/Error \[ERR_REQUIRE_ESM\]: Must use import to load ES Module:/));
+  assert.strictEqual(e.name, 'Error');
+  assert.strictEqual(e.code, 'ERR_REQUIRE_ESM');
+  assert(e.toString().match(/Must use import to load ES Module/g));
+  assert(e.message.match(/Must use import to load ES Module/g));
 }
 
 function expect(opt = '', inputFile, want, wantsError = false) {