Avoid empty-string errors on Currency field.

flask_admin/contrib/sqla/filters.py

@@ -440,8 +440,7 @@ class ChoiceTypeNotLikeFilter(FilterNotLike):
 class FilterConverter(filters.BaseFilterConverter):
     strings = (FilterLike, FilterNotLike, FilterEqual, FilterNotEqual,
                FilterEmpty, FilterInList, FilterNotInList)
-    string_key_filters = (FilterEqual, FilterNotEqual,
-               FilterEmpty, FilterInList, FilterNotInList)
+    string_key_filters = (FilterEqual, FilterNotEqual, FilterEmpty, FilterInList, FilterNotInList)
     int_filters = (IntEqualFilter, IntNotEqualFilter, IntGreaterFilter,
                    IntSmallerFilter, FilterEmpty, IntInListFilter,
                    IntNotInListFilter)
@@ -458,14 +457,11 @@ class FilterConverter(filters.BaseFilterConverter):
                         DateTimeGreaterFilter, DateTimeSmallerFilter,
                         DateTimeBetweenFilter, DateTimeNotBetweenFilter,
                         FilterEmpty)
-    time_filters = (TimeEqualFilter, TimeNotEqualFilter, TimeGreaterFilter,
-                    TimeSmallerFilter, TimeBetweenFilter, TimeNotBetweenFilter,
-                    FilterEmpty)
+    time_filters = (TimeEqualFilter, TimeNotEqualFilter, TimeGreaterFilter, TimeSmallerFilter,
+                    TimeBetweenFilter, TimeNotBetweenFilter, FilterEmpty)
     choice_type_filters = (ChoiceTypeEqualFilter, ChoiceTypeNotEqualFilter,
-                           ChoiceTypeLikeFilter, ChoiceTypeNotLikeFilter,
-                           FilterEmpty)
-    arrow_type_filters = (DateTimeGreaterFilter, DateTimeSmallerFilter, 
-                          FilterEmpty)
+                           ChoiceTypeLikeFilter, ChoiceTypeNotLikeFilter, FilterEmpty)
+    arrow_type_filters = (DateTimeGreaterFilter, DateTimeSmallerFilter, FilterEmpty)
 
     def convert(self, type_name, column, name, **kwargs):
         filter_name = type_name.lower()

flask_admin/contrib/sqla/form.py

@@ -367,6 +367,7 @@ class AdminModelConverter(ModelConverterBase):
     @converts('sqlalchemy_utils.types.currency.CurrencyType')
     def convert_currency(self, field_args, **extra):
         field_args['validators'].append(valid_currency)
+        field_args['filters'] = [avoid_empty_strings]  # don't accept empty strings, or whitespace
         return fields.StringField(**field_args)
 
     @converts('sqlalchemy_utils.types.timezone.TimezoneType')
@@ -422,6 +423,19 @@ class AdminModelConverter(ModelConverterBase):
         return form.JSONField(**field_args)
 
 
+def avoid_empty_strings(value):
+    """
+    Return None if the incoming value is an empty string or whitespace.
+    """
+    if value:
+        try:
+            value = value.strip()
+        except AttributeError:
+            # values are not always strings
+            pass
+    return value if value else None
+
+
 def choice_type_coerce_factory(type_):
     """
     Return a function to coerce a ChoiceType column, for use by Select2Field.