Fix splitting with split=False and maxsplit=0.

Since re.split behaves differently from str.split with maxsplit=0,
4e9b9baeab broke things like ":open foo bar".

qutebrowser/test/utils/test_split.py

@@ -157,6 +157,12 @@ class SimpleSplitTests(unittest.TestCase):
         self.assertEqual(split.simple_split(string, maxsplit=1),
                          string.split(maxsplit=1))
 
+    def test_str_split_maxsplit_0(self):
+        """Test if the behaviour matches str.split with maxsplit=0."""
+        string = "  foo bar baz  "
+        self.assertEqual(split.simple_split(string, maxsplit=0),
+                         string.split(maxsplit=0))
+
     def test_split_keep(self):
         """Test splitting with keep=True."""
         for test, expected in self.TESTS.items():

qutebrowser/utils/split.py

@@ -155,7 +155,7 @@ def split(s, keep=False):
     return out
 
 
-def simple_split(s, keep=False, maxsplit=0):
+def simple_split(s, keep=False, maxsplit=None):
     """Split a string on whitespace, optionally keeping the whitespace.
 
     Args:
@@ -167,6 +167,16 @@ def simple_split(s, keep=False, maxsplit=0):
         A list of split strings.
     """
     whitespace = '\n\t '
+    if maxsplit == 0:
+        # re.split with maxsplit=0 splits everything, while str.split splits
+        # nothing (which is the behaviour we want).
+        if keep:
+            return [s]
+        else:
+            return [s.lstrip(whitespace)]
+    elif maxsplit is None:
+        maxsplit = 0
+
     if keep:
         pattern = '([' + whitespace + '])'
     else: