Fixed #17888 -- no longer silence exceptions inside of check_test. Thanks to brutasse for the patch.

django/forms/widgets.py

@@ -507,11 +507,7 @@ class CheckboxInput(Widget):
 
     def render(self, name, value, attrs=None):
         final_attrs = self.build_attrs(attrs, type='checkbox', name=name)
-        try:
-            result = self.check_test(value)
-        except: # Silently catch exceptions
-            result = False
-        if result:
+        if self.check_test(value):
             final_attrs['checked'] = 'checked'
         if not (value is True or value is False or value is None or value == ''):
             # Only add the 'value' attribute if a value is non-empty.
@@ -525,7 +521,7 @@ class CheckboxInput(Widget):
             return False
         value = data.get(name)
         # Translate true and false strings to boolean values.
-        values =  {'true': True, 'false': False}
+        values = {'true': True, 'false': False}
         if isinstance(value, six.string_types):
             value = values.get(value.lower(), value)
         return value

docs/ref/forms/widgets.txt

@@ -310,6 +310,10 @@ commonly used groups of widgets:
         A callable that takes the value of the CheckBoxInput and returns
         ``True`` if the checkbox should be checked for that value.
 
+        .. versionchanged:: 1.5
+            Exceptions from ``check_test`` used to be silenced by its caller,
+            this is no longer the case, they will propagate upwards.
+
 ``Select``
 ~~~~~~~~~~
 

tests/regressiontests/forms/tests/widgets.py

@@ -216,13 +216,9 @@ class FormsWidgetTestCase(TestCase):
         self.assertHTMLEqual(w.render('greeting', 'hello there'), '<input checked="checked" type="checkbox" name="greeting" value="hello there" />')
         self.assertHTMLEqual(w.render('greeting', 'hello & goodbye'), '<input checked="checked" type="checkbox" name="greeting" value="hello &amp; goodbye" />')
 
-        # A subtlety: If the 'check_test' argument cannot handle a value and raises any
-        # exception during its __call__, then the exception will be swallowed and the box
-        # will not be checked. In this example, the 'check_test' assumes the value has a
-        # startswith() method, which fails for the values True, False and None.
-        self.assertHTMLEqual(w.render('greeting', True), '<input type="checkbox" name="greeting" />')
-        self.assertHTMLEqual(w.render('greeting', False), '<input type="checkbox" name="greeting" />')
-        self.assertHTMLEqual(w.render('greeting', None), '<input type="checkbox" name="greeting" />')
+        # Ticket #17888: calling check_test shouldn't swallow exceptions
+        with self.assertRaises(AttributeError):
+            w.render('greeting', True)
 
         # The CheckboxInput widget will return False if the key is not found in the data
         # dictionary (because HTML form submission doesn't send any result for unchecked