Make skip_filter work for built-in functions (#69)

spitfire/runtime/filters.py

@@ -5,6 +5,8 @@
 
 # a few helpful filter functions
 
+import functools
+import types
 from spitfire import runtime
 from spitfire.runtime import udn
 
@@ -14,6 +16,15 @@
 # create data that could be double-escaped and you don't wnat to constantly
 # inform spitfire to us raw mode.
 def skip_filter(function):
+    if isinstance(function, types.BuiltinFunctionType):
+        # Built-in functions don't allow abitrary attributes, so we use a
+        # wrapper function that just passes through
+        @functools.wraps(function)
+        def skip_filter_wrapper(*args, **kwargs):
+            return function(*args, **kwargs)
+        skip_filter_wrapper.skip_filter = True
+        return skip_filter_wrapper
+
     function.skip_filter = True
     return function
 

spitfire/runtime/template_test.py

@@ -3,8 +3,10 @@
 # Use of this source code is governed by a BSD-style
 # license that can be found in the LICENSE file.
 
+import sys
 import unittest
 
+from spitfire.runtime import filters
 from spitfire.runtime import template
 from spitfire.runtime import baked
 try:
@@ -13,17 +15,14 @@
     _template = None
 
 
+@filters.skip_filter
 def is_skip():
     pass
 
 
-is_skip.skip_filter = True
-
-
 def no_skip():
     pass
 
-
 # Do not inherit from unittest.TestCase to ensure that these tests don't run.
 # Add tests here and they will be run for the C and Python implementations. This
 # should make sure that both implementations are equivalent.
@@ -38,6 +37,15 @@ def setUp(self):
     def test_skip_filter(self):
         self.assertEqual(self.template.filter_function('foo', is_skip), 'foo')
 
+    def test_skip_filter_builtin(self):
+        # Ensure skip_filter works for built-in functions as well,
+        # choice of getdefaultencoding is abitrary - it's a built-in function
+        is_skip_builtin = filters.skip_filter(sys.getdefaultencoding)
+        self.assertEqual(self.template.filter_function('foo', is_skip_builtin),
+                         'foo')
+        # Ensure wrapped function works as expected
+        self.assertEqual(is_skip_builtin(), sys.getdefaultencoding())
+
     def test_no_skip(self):
         self.assertEqual(
             self.template.filter_function('foo', no_skip), 'FILTERED')