Fixed #29400 -- Fixed crash in custom template filters that use decorated functions.

Regression in 620e9dd31a.

tests/template_tests/templatetags/custom.py

@@ -3,6 +3,7 @@ import operator
 from django import template
 from django.template.defaultfilters import stringfilter
 from django.utils.html import escape, format_html
+from django.utils.safestring import mark_safe
 
 register = template.Library()
 
@@ -13,6 +14,13 @@ def trim(value, num):
     return value[:num]
 
 
+@register.filter
+@mark_safe
+def make_data_div(value):
+    """A filter that uses a decorator (@mark_safe)."""
+    return '<div data-name="%s"></div>' % value
+
+
 @register.filter
 def noop(value, param=None):
     """A noop filter that always return its first argument and does nothing with

tests/template_tests/test_custom.py

@@ -25,6 +25,11 @@ class CustomFilterTests(SimpleTestCase):
             "abcde"
         )
 
+    def test_decorated_filter(self):
+        engine = Engine(libraries=LIBRARIES)
+        t = engine.from_string('{% load custom %}{{ name|make_data_div }}')
+        self.assertEqual(t.render(Context({'name': 'foo'})), '<div data-name="foo"></div>')
+
 
 class TagTestCase(SimpleTestCase):