fields: consider the empty string as a valid (null) date (#23162)

tests/test_hobo_notify.py

@@ -582,7 +582,7 @@ def test_process_notification_user_provision(pub):
         }
         CmdHoboNotify.process_notification(notification)
         assert User.count() == 1
-        if birthdate is not None:  # wrong value : no nothing
+        if birthdate not in (None, ''):  # wrong value : no nothing
             assert User.select()[0].form_data['_birthdate'].tm_year == 2000
         else:  # empty value : empty field
             assert User.select()[0].form_data['_birthdate'] is None

tests/test_workflows.py

@@ -2919,13 +2919,15 @@ def test_profile(two_pubs):
             assert http_patch_request.call_count == 1
             assert http_patch_request.call_args[0][1] == '{"bar": "2018-03-20"}'
 
-    user.form_data['4'] = datetime.datetime.now().timetuple()
-    user.store()
-    year = User.get(user.id).form_data.get('4').tm_year
     for date_value in ('baddate', '', {}, [], None):
+        # reset date to a known value
+        user.form_data['4'] = datetime.datetime.now().timetuple()
+        user.store()
+        year = User.get(user.id).form_data.get('4').tm_year
+        # perform action
         item.fields = [{'field_id': 'bar', 'value': date_value}]
         item.perform(formdata)
-        if date_value is not None:  # bad value : do nothing
+        if date_value not in (None, ''):  # bad value : do nothing
             assert User.get(user.id).form_data.get('4').tm_year == year
         else:  # empty value : empty field
             assert User.get(user.id).form_data.get('4') == None
@@ -2934,7 +2936,7 @@ def test_profile(two_pubs):
             http_patch_request.return_value = (None, 200, '', None)
             get_response().process_after_jobs()
             assert http_patch_request.call_count == 1
-            if date_value is not None:  # bad value : do nothing
+            if date_value not in (None, ''):  # bad value : do nothing
                 assert http_patch_request.call_args[0][1] == '{}'
             else:  # empty value : null field
                 assert http_patch_request.call_args[0][1] == '{"bar": null}'
@@ -3282,7 +3284,7 @@ def test_set_backoffice_field_date(two_pubs):
     assert datetime.date(*formdata.data['bo1'][:3]) == datetime.date(2017, 3, 23)
 
     # invalid values => do nothing
-    for value in ('plop', '', {}, [], '{{ blah }}'):
+    for value in ('plop', {}, []):
         item = SetBackofficeFieldsWorkflowStatusItem()
         item.parent = st1
         item.fields = [{'field_id': 'bo1', 'value': value}]

wcs/fields.py

@@ -980,7 +980,7 @@ class DateField(WidgetField):
 
     @classmethod
     def convert_value_from_anything(cls, value):
-        if value is None:
+        if value is None or value == '':
             return None
         date_value = evalutils.make_date(value).timetuple()  # could raise ValueError
         return date_value