From 19e940d17c578ed30ea988bf6f8d2941cdd30214 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Heath=20Dutton=F0=9F=95=B4=EF=B8=8F?=
 <heathdutton@gmail.com>
Date: Wed, 24 Dec 2025 23:09:20 -0500
Subject: [PATCH] module: fix silent failure for ESM syntax in explicit
 commonjs entry

When a main entry point contains ESM syntax but is in a package with
"type": "commonjs" in package.json, the module would silently exit
with code 0 without executing or showing any error.

This fix ensures that when the file is in a package with explicit
"type": "commonjs", shouldDetectModule is set to false in wrapSafe,
so the native compiler throws the proper SyntaxError with source
line information rather than detecting it as a module and deferring
to ESM loading (which caused the silent failure).

Fixes: https://github.com/nodejs/node/issues/61104
---
 lib/internal/modules/cjs/loader.js            | 21 ++++++++++++-------
 test/es-module/test-esm-syntax-in-cjs-main.js | 19 +++++++++++++++++
 .../esm-script.js                             |  4 ++++
 .../package.json                              |  3 +++
 4 files changed, 40 insertions(+), 7 deletions(-)
 create mode 100644 test/es-module/test-esm-syntax-in-cjs-main.js
 create mode 100644 test/fixtures/es-modules/package-type-commonjs-esm-syntax/esm-script.js
 create mode 100644 test/fixtures/es-modules/package-type-commonjs-esm-syntax/package.json

diff --git a/lib/internal/modules/cjs/loader.js b/lib/internal/modules/cjs/loader.js
index d9fc92bbc813e8..e319ff99f1fa3e 100644
--- a/lib/internal/modules/cjs/loader.js
+++ b/lib/internal/modules/cjs/loader.js
@@ -1722,13 +1722,20 @@ function wrapSafe(filename, content, cjsModuleInstance, format) {
 
   let shouldDetectModule = false;
   if (format !== 'commonjs') {
-    if (cjsModuleInstance?.[kIsMainSymbol]) {
-      // For entry points, format detection is used unless explicitly disabled.
-      shouldDetectModule = getOptionValue('--experimental-detect-module');
-    } else {
-      // For modules being loaded by `require()`, if require(esm) is disabled,
-      // don't try to reparse to detect format and just throw for ESM syntax.
-      shouldDetectModule = getOptionValue('--require-module');
+    // Also check if we're in an explicit commonjs package, even if format wasn't
+    // set (e.g., for extensionless files). In explicit commonjs packages, we should
+    // not detect module syntax and instead let the syntax error propagate.
+    const pkg = packageJsonReader.getNearestParentPackageJSON(filename);
+    const explicitCommonJS = pkg?.data.type === 'commonjs';
+    if (!explicitCommonJS) {
+      if (cjsModuleInstance?.[kIsMainSymbol]) {
+        // For entry points, format detection is used unless explicitly disabled.
+        shouldDetectModule = getOptionValue('--experimental-detect-module');
+      } else {
+        // For modules being loaded by `require()`, if require(esm) is disabled,
+        // don't try to reparse to detect format and just throw for ESM syntax.
+        shouldDetectModule = getOptionValue('--require-module');
+      }
     }
   }
   const result = compileFunctionForCJSLoader(content, filename, false /* is_sea_main */, shouldDetectModule);
diff --git a/test/es-module/test-esm-syntax-in-cjs-main.js b/test/es-module/test-esm-syntax-in-cjs-main.js
new file mode 100644
index 00000000000000..2c3987308a597b
--- /dev/null
+++ b/test/es-module/test-esm-syntax-in-cjs-main.js
@@ -0,0 +1,19 @@
+// Flags: --no-warnings
+'use strict';
+
+// Test that running a main entry point with ESM syntax in a "type": "commonjs"
+// package throws an error instead of silently failing with exit code 0.
+// Regression test for https://github.com/nodejs/node/issues/61104
+
+require('../common');
+const { spawnSyncAndAssert } = require('../common/child_process');
+const fixtures = require('../common/fixtures.js');
+const { execPath } = require('node:process');
+
+const mainScript = fixtures.path('es-modules/package-type-commonjs-esm-syntax/esm-script.js');
+
+spawnSyncAndAssert(execPath, [mainScript], {
+  status: 1,
+  signal: null,
+  stderr: /import { version } from 'node:process'/,
+});
diff --git a/test/fixtures/es-modules/package-type-commonjs-esm-syntax/esm-script.js b/test/fixtures/es-modules/package-type-commonjs-esm-syntax/esm-script.js
new file mode 100644
index 00000000000000..4cabb2a94dbeae
--- /dev/null
+++ b/test/fixtures/es-modules/package-type-commonjs-esm-syntax/esm-script.js
@@ -0,0 +1,4 @@
+// This file has ESM syntax but is in a "type": "commonjs" package
+console.log('script STARTED');
+import { version } from 'node:process';
+console.log(version);
diff --git a/test/fixtures/es-modules/package-type-commonjs-esm-syntax/package.json b/test/fixtures/es-modules/package-type-commonjs-esm-syntax/package.json
new file mode 100644
index 00000000000000..5bbefffbabee39
--- /dev/null
+++ b/test/fixtures/es-modules/package-type-commonjs-esm-syntax/package.json
@@ -0,0 +1,3 @@
+{
+  "type": "commonjs"
+}