From 6a73714b00279647297f599ff57855ec2b12efd0 Mon Sep 17 00:00:00 2001
From: Daniel Hahler <git@thequod.de>
Date: Sun, 14 Apr 2019 19:00:46 +0200
Subject: [PATCH] deselect_by_keyword: skip without expression

There is no need to iterate over all items always, if `-k` is not
specified.
---
 src/_pytest/mark/__init__.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/_pytest/mark/__init__.py b/src/_pytest/mark/__init__.py
index ef81784f4..e98dc5c37 100644
--- a/src/_pytest/mark/__init__.py
+++ b/src/_pytest/mark/__init__.py
@@ -100,6 +100,9 @@ pytest_cmdline_main.tryfirst = True
 
 def deselect_by_keyword(items, config):
     keywordexpr = config.option.keyword.lstrip()
+    if not keywordexpr:
+        return
+
     if keywordexpr.startswith("-"):
         keywordexpr = "not " + keywordexpr[1:]
     selectuntil = False