gh-152686: Quote '!' in venv activate.csh for (t)csh

Lib/test/test_venv.py

@@ -773,6 +773,30 @@ def test_special_chars_csh(self):
         self.assertTrue(env_name.encode() in lines[0])
         self.assertEndsWith(lines[1], env_name.encode())
 
+    # gh-152686: '!' triggers csh history expansion even inside single quotes
+    @unittest.skipIf(os.name == 'nt', 'contains invalid characters on Windows')
+    @unittest.skipIf(sys.platform.startswith('netbsd'),
+                     "NetBSD csh fails with quoted special chars; see gh-139308")
+    def test_special_chars_csh_prompt(self):
+        """
+        Test that a '!' in the prompt is quoted properly (csh)
+        """
+        rmtree(self.env_dir)
+        csh = shutil.which('tcsh') or shutil.which('csh')
+        if csh is None:
+            self.skipTest('csh required for this test')
+        prompt = 'py!env'
+        builder = venv.EnvBuilder(clear=True, prompt=prompt)
+        builder.create(self.env_dir)
+        activate = os.path.join(self.env_dir, self.bindir, 'activate.csh')
+        test_script = os.path.join(self.env_dir, 'test_special_chars_prompt.csh')
+        with open(test_script, "w") as f:
+            f.write(f'source {shlex.quote(activate)}\n'
+                    'python -c \'import os; print(os.environ["VIRTUAL_ENV_PROMPT"])\'\n'
+                    'deactivate\n')
+        out, err = check_output([csh, test_script])
+        self.assertEndsWith(out.splitlines()[-1], prompt.encode())
+
     # gh-140006: the fish prompt override must keep working when a user
     # function shadows a builtin it relies on.
     @unittest.skipIf(os.name == 'nt', 'fish is not available on Windows')

Lib/venv/__init__.py

@@ -519,13 +519,20 @@ def quote_ps1(s):
         def quote_bat(s):
             return s
 
+        def quote_csh(s):
+            # (t)csh history-expands '!' even inside single quotes, so POSIX
+            # quoting is not enough; escape each '!' explicitly.
+            return shlex.quote(s).replace('!', "'\\!'")
+
         # gh-124651: need to quote the template strings properly
         quote = shlex.quote
         script_path = context.script_path
         if script_path.endswith('.ps1'):
             quote = quote_ps1
         elif script_path.endswith('.bat'):
             quote = quote_bat
+        elif script_path.endswith('.csh'):
+            quote = quote_csh
         else:
             # fallbacks to POSIX shell compliant quote
             quote = shlex.quote

Misc/NEWS.d/next/Library/2026-06-30-13-00-00.gh-issue-152686.vcsh01.rst

@@ -0,0 +1,3 @@
+Fix :mod:`venv` activation under (t)csh for environments whose path or
+``--prompt`` contains ``!``: ``activate.csh`` is now quoted so that csh does
+not perform history expansion on it.