module: trim off internal stack frames for require(esm) warnings

lib/internal/modules/cjs/loader.js

@@ -1389,7 +1389,10 @@ function loadESMFromCJS(mod, filename) {
         messagePrefix = `${from} is loading ES Module ${to} using require().\n`;
       }
     }
-    emitExperimentalWarning('Support for loading ES Module in require()', messagePrefix);
+    emitExperimentalWarning('Support for loading ES Module in require()',
+                            messagePrefix,
+                            undefined,
+                            parent?.require);
     const {
       wrap,
       namespace,

lib/internal/util.js

@@ -266,14 +266,20 @@ function slowCases(enc) {
   }
 }
 
-function emitExperimentalWarning(feature, messagePrefix) {
+/**
+ * @param {string} feature Feature name used in the warning message
+ * @param {string} messagePrefix Prefix of the warning message
+ * @param {string} code See documentation of process.emitWarning
+ * @param {string} ctor See documentation of process.emitWarning
+ */
+function emitExperimentalWarning(feature, messagePrefix, code, ctor) {
   if (experimentalWarnings.has(feature)) return;
   experimentalWarnings.add(feature);
   let msg = `${feature} is an experimental feature and might change at any time`;
   if (messagePrefix) {
     msg = messagePrefix + msg;
   }
-  process.emitWarning(msg, 'ExperimentalWarning');
+  process.emitWarning(msg, 'ExperimentalWarning', code, ctor);
 }
 
 function filterDuplicateStrings(items, low) {

test/es-module/test-require-module-warning.js

@@ -0,0 +1,35 @@
+'use strict';
+
+// This checks the warning and the stack trace emitted by the require(esm)
+// experimental warning. It can get removed when `require(esm)` becomes stable.
+
+require('../common');
+const { spawnSyncAndAssert } = require('../common/child_process');
+const fixtures = require('../common/fixtures');
+const assert = require('assert');
+
+spawnSyncAndAssert(process.execPath, [
+  '--trace-warnings',
+  fixtures.path('es-modules', 'require-module.js'),
+], {
+  trim: true,
+  stderr(output) {
+    const lines = output.split('\n');
+    assert.match(
+      lines[0],
+      /ExperimentalWarning: CommonJS module .*require-module\.js is loading ES Module .*message\.mjs/
+    );
+    assert.strictEqual(
+      lines[1],
+      'Support for loading ES Module in require() is an experimental feature and might change at any time'
+    );
+    assert.match(
+      lines[2],
+      /at require \(.*modules\/helpers:\d+:\d+\)/
+    );
+    assert.match(
+      lines[3],
+      /at Object\.<anonymous> \(.*require-module\.js:1:1\)/
+    );
+  }
+});

test/fixtures/es-modules/require-module.js

@@ -0,0 +1 @@
+require('./message.mjs');