Prevent invalid data to be silently accepted

When a user wants sets a ``Date`` or ``Datetime`` value and misses
one of the fields (day, year, hour or minute) it is silently set to
None without any 'input is not valid' error message being displayed.

Unfortunately it can not be checked on a validator because the input
value has already been converted to a ``datetime``.

This commit works around it making sure an error is raised and only
convert it to None if both *day* and *year* are left empty.

HISTORY.rst

@@ -4,8 +4,8 @@ Changelog
 1.2.8 (unreleased)
 ------------------
 
-- Nothing changed yet.
-
+- Prevent invalid data to be silently accepted.
+  [bogdangi]
 
 1.2.7 (2015-04-29)
 ------------------

src/collective/z3cform/datetimewidget/converter.py

@@ -25,16 +25,21 @@
 from collective.z3cform.datetimewidget.interfaces import DateValidationError, DatetimeValidationError
 
 class DateDataConverter(BaseDataConverter):
-    
+
     def toWidgetValue(self, value):
         if value is self.field.missing_value:
             return ('', '', '')
         return (value.year, value.month, value.day)
 
     def toFieldValue(self, value):
-        for val in value:
-            if not val:
-                return self.field.missing_value
+        if len(value) != 3:
+            raise DateValidationError
+
+        year, month, day = value
+
+        if not year \
+                and not day:
+            return self.field.missing_value
 
         try:
             value = map(int, value)
@@ -46,16 +51,21 @@ def toFieldValue(self, value):
             raise DateValidationError
 
 class DatetimeDataConverter(DateDataConverter):
-    
+
     def toWidgetValue(self, value):
         if value is self.field.missing_value:
             return ('', '', '', '00', '00')
         return (value.year, value.month, value.day, value.hour, value.minute)
 
     def toFieldValue(self, value):
-        for val in value:
-            if not val:
-                return self.field.missing_value
+        if len(value) != 5:
+            raise DatetimeValidationError
+
+        year, month, day, hour, minute = value
+
+        if not year \
+                and not day:
+            return self.field.missing_value
 
         try:
             value = map(int, value)

src/collective/z3cform/datetimewidget/converter.txt

@@ -37,10 +37,10 @@ We can also convert widget values to field values.
     >>> converter.toFieldValue(('2009', '5', '10'))
     datetime.date(2009, 5, 10)
 
-If any of the widget value components is missing, a value of None will be
+If day and year of the widget value components is missing, a value of None will be
 returned.
 
-    >>> converter.toFieldValue(('', '5', '10')) is None
+    >>> converter.toFieldValue(('', '5', '')) is None
     True
 
 If all of the widget value components are present but they don't correspond to
@@ -52,3 +52,42 @@ a valid date, a validation error will be raised.
     DateValidationError
 
 
+Let's set up a datetime field, datetime widget, and a converter adapting both of them.
+
+    >>> from zope.schema import Datetime
+    >>> from collective.z3cform.datetimewidget import DatetimeWidget
+    >>> from collective.z3cform.datetimewidget.converter import DatetimeDataConverter
+    >>> field = Datetime()
+    >>> request = TestRequest()
+    >>> widget = DatetimeWidget(request)
+    >>> converter = DatetimeDataConverter(field, widget)
+
+Now we can convert field values to widget values.
+
+    >>> from datetime import datetime
+    >>> converter.toWidgetValue(datetime(2009, 5, 10, 15, 35))
+    (2009, 5, 10, 15, 35)
+
+A value of None results in a tuple of empty strings.
+
+    >>> converter.toWidgetValue(None)
+    ('', '', '', '00', '00')
+
+We can also convert widget values to field values.
+
+    >>> converter.toFieldValue(('2009', '5', '10', '15', '35'))
+    datetime.datetime(2009, 5, 10, 15, 35)
+
+If day and year of the widget value components is missing, a value of None will be
+returned.
+
+    >>> converter.toFieldValue(('', '5', '', '00', '00')) is None
+    True
+
+If all of the widget value components are present but they don't correspond to
+a valid date, a validation error will be raised.
+
+    >>> converter.toFieldValue(('2009', '42', '42', '42', '82'))
+    Traceback (most recent call last):
+    ...
+    DatetimeValidationError