use soft_str in do_wordcount, to trigger undefined

CHANGES.rst

@@ -8,7 +8,8 @@ Unreleased
 -   Fix a bug that caused callable objects with ``__getattr__``, like
     :class:`~unittest.mock.Mock` to be treated as a
     :func:`contextfunction`. :issue:`1145`
-
+-   Update ``wordcount`` filter to trigger :class:`Undefined` methods
+    by wrapping the input in :func:`soft_unicode`. :pr:`1160`
 
 
 Version 2.11.1

src/jinja2/filters.py

@@ -761,7 +761,7 @@ def do_wordwrap(
 
 def do_wordcount(s):
     """Count the words in that string."""
-    return len(_word_re.findall(s))
+    return len(_word_re.findall(soft_unicode(s)))
 
 
 def do_int(value, default=0, base=10):

tests/test_filters.py

@@ -6,6 +6,8 @@ import pytest
 
 from jinja2 import Environment
 from jinja2 import Markup
+from jinja2 import StrictUndefined
+from jinja2 import UndefinedError
 from jinja2._compat import implements_to_string
 from jinja2._compat import text_type
 
@@ -369,6 +371,11 @@ class TestFilter(object):
         tmpl = env.from_string('{{ "foo bar baz"|wordcount }}')
         assert tmpl.render() == "3"
 
+        strict_env = Environment(undefined=StrictUndefined)
+        t = strict_env.from_string("{{ s|wordcount }}")
+        with pytest.raises(UndefinedError):
+            t.render()
+
     def test_block(self, env):
         tmpl = env.from_string("{% filter lower|escape %}<HEHE>{% endfilter %}")
         assert tmpl.render() == "&lt;hehe&gt;"