From de96d738ebfd206810e2e216bd571895fa2ac0f6 Mon Sep 17 00:00:00 2001
From: Allan Olweny <allan.olweny+github@gmail.com>
Date: Sat, 18 May 2024 14:28:36 -0400
Subject: [PATCH] Add warning for an empty group in the message string

---
 src/_pytest/config/__init__.py | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/_pytest/config/__init__.py b/src/_pytest/config/__init__.py
index c698ea9a777..1bae77c87c6 100644
--- a/src/_pytest/config/__init__.py
+++ b/src/_pytest/config/__init__.py
@@ -1924,6 +1924,13 @@ def parse_warning_filter(
         raise UsageError(error_template.format(error=exception_text)) from None
     if message and escape:
         message = re.escape(message)
+    if "()" in message:
+        warning = dedent(
+            """
+            An empty group '()' will not match a string that contains literal parenthesis
+            """
+        )
+        warnings.warn(PytestConfigWarning(warning))
     if module and escape:
         module = re.escape(module) + r"\Z"
     if lineno_: