From f83a3e024a2d554795a6294f747a1f7b05e82553 Mon Sep 17 00:00:00 2001
From: Arya Mirani <aryamirani06@gmail.com>
Date: Thu, 23 Jul 2026 10:00:23 +0530
Subject: [PATCH] Fix view engine resolution for view names ending in a dot

When a view name ends in a dot (e.g. 'index.'), path.extname returns '.',
causing mod to evaluate to an empty string ('' '') and throwing an opaque
TypeError [ERR_INVALID_ARG_VALUE] when require('') is called inside View constructor.

This change treats '.' as an unprovided extension when engines['.'] is not
explicitly registered, allowing view engine fallback to defaultEngine or
returning a clean view lookup error.

Fixes #7350
---
 lib/view.js        |  4 ++--
 test/app.render.js | 12 ++++++++++++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/lib/view.js b/lib/view.js
index d66b4a2d89c..0dbe6a5cc8c 100644
--- a/lib/view.js
+++ b/lib/view.js
@@ -57,13 +57,13 @@ function View(name, options) {
   this.name = name;
   this.root = opts.root;
 
-  if (!this.ext && !this.defaultEngine) {
+  if ((!this.ext || (this.ext === '.' && !opts.engines[this.ext])) && !this.defaultEngine) {
     throw new Error('No default engine was specified and no extension was provided.');
   }
 
   var fileName = name;
 
-  if (!this.ext) {
+  if (!this.ext || (this.ext === '.' && !opts.engines[this.ext])) {
     // get extension from default engine name
     this.ext = this.defaultEngine[0] !== '.'
       ? '.' + this.defaultEngine
diff --git a/test/app.render.js b/test/app.render.js
index bd65ce1035b..770970aeb2d 100644
--- a/test/app.render.js
+++ b/test/app.render.js
@@ -90,6 +90,18 @@ describe('app', function(){
           done();
         });
       })
+
+      it('should provide a helpful error when view name ends in a dot', function(done){
+        var app = createApp();
+
+        app.set('views', path.join(__dirname, 'fixtures'))
+        app.set('view engine', 'tmpl');
+        app.render('rawr.', function (err) {
+          assert.ok(err)
+          assert.equal(err.message, 'Failed to lookup view "rawr." in views directory "' + path.join(__dirname, 'fixtures') + '"')
+          done();
+        });
+      })
     })
 
     describe('when an error occurs', function(){