Added a workaround for Python bug 13598

2 files changed, 37 insertions, 2 deletions

diff --git a/markupsafe/__init__.py b/markupsafe/__init__.py
index 6040dc1..2755401 100644
--- a/markupsafe/__init__.py
+++ b/markupsafe/__init__.py
@@ -10,6 +10,7 @@
 """
 import re
 import string
+from collections import Mapping
 from markupsafe._compat import text_type, string_types, int_types, \
      unichr, iteritems, PY2
 
@@ -196,7 +197,8 @@ class Markup(text_type):
         def format(*args, **kwargs):
             self, args = args[0], args[1:]
             formatter = EscapeFormatter(self.escape)
-            return self.__class__(formatter.format(self, *args, **kwargs))
+            kwargs = _MagicFormatMapping(args, kwargs)
+            return self.__class__(formatter.vformat(self, args, kwargs))
 
         def __html_format__(self, format_spec):
             if format_spec:
@@ -211,6 +213,37 @@ class Markup(text_type):
     del method, make_simple_escaping_wrapper
 
 
+class _MagicFormatMapping(Mapping):
+    """This class implements a dummy wrapper to fix a bug in the Python
+    standard library for string formatting.
+
+    See http://bugs.python.org/issue13598 for information about why
+    this is necessary.
+    """
+
+    def __init__(self, args, kwargs):
+        self._args = args
+        self._kwargs = kwargs
+        self._last_index = 0
+
+    def __getitem__(self, key):
+        if key == '':
+            idx = self._last_index
+            self._last_index += 1
+            try:
+                return self._args[idx]
+            except LookupError:
+                pass
+            key = str(idx)
+        return self._kwargs[key]
+
+    def __iter__(self):
+        return iter(self._kwargs)
+
+    def __len__(self):
+        return len(self._kwargs)
+
+
 if hasattr(text_type, 'format'):
     class EscapeFormatter(string.Formatter):
 
diff --git a/markupsafe/tests.py b/markupsafe/tests.py
index 0731926..02083c6 100644
--- a/markupsafe/tests.py
+++ b/markupsafe/tests.py
@@ -75,7 +75,9 @@ class MarkupTestCase(unittest.TestCase):
             (Markup('{0[1][bar]}').format([0, {'bar': '<bar/>'}]),
              '&lt;bar/&gt;'),
             (Markup('{0[1][bar]}').format([0, {'bar': Markup('<bar/>')}]),
-             '<bar/>')):
+             '<bar/>'),
+            (Markup('{}').format(0),
+             Markup('0'))):
             assert actual == expected, "%r should be %r!" % (actual, expected)
 
     def test_custom_formatting(self):