[Piglit] [PATCH 3/7] framework/grouptools: fix commonprefix with empty value

[Dylan Baker]

---
 framework/grouptools.py             | 2 ++
 framework/tests/grouptools_tests.py | 8 ++++++++
 2 files changed, 10 insertions(+)

diff --git a/framework/grouptools.py b/framework/grouptools.py
index 81e6091..d6749d6 100644
--- a/framework/grouptools.py
+++ b/framework/grouptools.py
@@ -81,6 +81,8 @@ def commonprefix(args):
     """Given a list of groups, returns the longest common leading component."""
     if len(args) == 1:
         return args
+    elif any(e == '' for e in args):
+        return ''
 
     common = []
 
diff --git a/framework/tests/grouptools_tests.py b/framework/tests/grouptools_tests.py
index e41ad2c..e3b4ee0 100644
--- a/framework/tests/grouptools_tests.py
+++ b/framework/tests/grouptools_tests.py
@@ -99,3 +99,11 @@ def test_from_path_nt():
 def test_from_path_dot():
     """grouptools.from_path: should convert '.' into ''."""
     nt.assert_equal(grouptools.from_path('.'), '')
+
+
+def test_commonprefix_empty():
+    """grouptools.commonprefix: handles an empty value"""
+    expected = ''
+    value = grouptools.commonprefix((grouptools.join('foo', 'bar'), ''))
+
+    nt.eq_(expected, value)
-- 
2.5.1