From 5de2c148c01dfb866c2f51ea94d41ba19071815e Mon Sep 17 00:00:00 2001
From: Errr0rr404 <37506695+Errr0rr404@users.noreply.github.com>
Date: Thu, 23 Jul 2026 12:31:48 -0400
Subject: [PATCH] fix(view): avoid opaque TypeError for view names ending in
 "."

path.extname('index.') returns '.', so the engine loader called
require('') and threw ERR_INVALID_ARG_VALUE before lookup could fail
cleanly. Skip loading when the extension body is empty so app.render
returns the usual "Failed to lookup view" error instead.

Fixes #7350
---
 lib/view.js        | 20 +++++++++++++-------
 test/app.render.js | 12 ++++++++++++
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/lib/view.js b/lib/view.js
index d66b4a2d89c..37c72ef19a1 100644
--- a/lib/view.js
+++ b/lib/view.js
@@ -75,16 +75,22 @@ function View(name, options) {
   if (!opts.engines[this.ext]) {
     // load engine
     var mod = this.ext.slice(1)
-    debug('require "%s"', mod)
 
-    // default engine export
-    var fn = require(mod).__express
+    // path.extname('index.') returns '.', so mod is ''. Avoid require('')
+    // which throws an opaque TypeError; leave the engine unset so lookup
+    // fails cleanly with "Failed to lookup view".
+    if (mod) {
+      debug('require "%s"', mod)
 
-    if (typeof fn !== 'function') {
-      throw new Error('Module "' + mod + '" does not provide a view engine.')
-    }
+      // default engine export
+      var fn = require(mod).__express
+
+      if (typeof fn !== 'function') {
+        throw new Error('Module "' + mod + '" does not provide a view engine.')
+      }
 
-    opts.engines[this.ext] = fn
+      opts.engines[this.ext] = fn
+    }
   }
 
   // store loaded engine
diff --git a/test/app.render.js b/test/app.render.js
index bd65ce1035b..a627d7d6bf7 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 for a name ending in "."', function(done){
+        var app = createApp();
+
+        app.set('views', path.join(__dirname, 'fixtures'))
+        app.set('view engine', 'tmpl')
+        app.render('index.', function (err) {
+          assert.ok(err)
+          assert.ok(err.message.indexOf('Failed to lookup view "index."') === 0)
+          done();
+        });
+      })
     })
 
     describe('when an error occurs', function(){