From 4ead5c71a1e7aec611cee2d0ffda8dd3e8832948 Mon Sep 17 00:00:00 2001
From: Evan <evanunderscore@gmail.com>
Date: Mon, 4 Sep 2017 21:40:56 +1000
Subject: [PATCH] Fix crash in FastFilesCompleter with no prefix

---
 _pytest/_argcomplete.py | 5 +++--
 changelog/2748.bugfix   | 1 +
 2 files changed, 4 insertions(+), 2 deletions(-)
 create mode 100644 changelog/2748.bugfix

diff --git a/_pytest/_argcomplete.py b/_pytest/_argcomplete.py
index 1ba1ecc1e7c..5cf44267c58 100644
--- a/_pytest/_argcomplete.py
+++ b/_pytest/_argcomplete.py
@@ -78,7 +78,8 @@ def __call__(self, prefix, **kwargs):
         completion = []
         globbed = []
         if '*' not in prefix and '?' not in prefix:
-            if prefix[-1] == os.path.sep:  # we are on unix, otherwise no bash
+            # we are on unix, otherwise no bash
+            if prefix and prefix[-1] == os.path.sep:
                 globbed.extend(glob(prefix + '.*'))
             prefix += '*'
         globbed.extend(glob(prefix))
@@ -98,7 +99,7 @@ def __call__(self, prefix, **kwargs):
     filescompleter = FastFilesCompleter()
 
     def try_argcomplete(parser):
-        argcomplete.autocomplete(parser)
+        argcomplete.autocomplete(parser, always_complete_options=False)
 else:
     def try_argcomplete(parser):
         pass
diff --git a/changelog/2748.bugfix b/changelog/2748.bugfix
new file mode 100644
index 00000000000..b5b6f583990
--- /dev/null
+++ b/changelog/2748.bugfix
@@ -0,0 +1 @@
+Fix crash in tab completion when no prefix is given.