NumberRange can handle NaN values

CHANGES.rst

@@ -67,6 +67,8 @@ Unreleased
 -   :class:`~validators.URL` validator now allows query parameters in the URL. (:pr:`523`, :pr:`524`).
 -   Updated French and Japanese translations. (:pr:`514`, :pr:`506`)
 -   form.errors is not cached and will update if an error is appended to a field after access. (:pr:`568`)
+-   :class:`~wtforms.validators.NumberRange` correctly handle *not a number*
+    values. (:pr:`505`, :pr:`548`)
 
 
 Version 2.2.1

src/wtforms/validators.py

@@ -1,5 +1,6 @@
 from __future__ import unicode_literals
 
+import math
 import re
 import uuid
 
@@ -191,6 +192,7 @@ def __call__(self, form, field):
         data = field.data
         if (
             data is None
+            or math.isnan(data)
             or (self.min is not None and data < self.min)
             or (self.max is not None and data > self.max)
         ):

tests/test_validators.py

@@ -1,4 +1,5 @@
 # -*- coding: utf-8 -*-
+import decimal
 import pytest
 import re
 
@@ -589,6 +590,14 @@ def test_number_range_raises(min_v, max_v, test_v, dummy_form, dummy_field):
         validator(dummy_form, dummy_field)
 
 
+@pytest.mark.parametrize("nan", [float("NaN"), decimal.Decimal("NaN")])
+def test_number_range_nan(nan, dummy_form, dummy_field):
+    validator = NumberRange(0, 10)
+    dummy_field.data = nan
+    with pytest.raises(ValidationError):
+        validator(dummy_form, dummy_field)
+
+
 @pytest.mark.parametrize("test_function", [str, text_type])
 def test_lazy_proxy_raises(test_function, really_lazy_proxy):
     """