Enable customization of SimpleListField

django_mysql/forms.py

@@ -18,11 +18,29 @@
 
 class SimpleListField(forms.CharField):
 
+    # These bits can be overridden simply to change the way the field works
+
     default_error_messages = {
         'item_n_invalid': _('Item %(nth)s in the list did not validate: '),
-        'no_double_commas': _('No leading, trailing, or double commas.'),
+        'items_no_commas': _('No leading, trailing, or double commas.'),
+        # The 'empty' message is the same as 'no commas' by default, since the
+        # only reason empty strings could arise with the basic comma-splitting
+        # logic is with extra commas. This may not be true in custom subclasses
+        # however.
+        'items_no_empty': _('No leading, trailing, or double commas.'),
     }
 
+    def prepare_value_serialize(self, values):
+        return ",".join(values)
+
+    def to_python_deserialize(self, value):
+        if not value:
+            return []
+        else:
+            return value.split(",")
+
+    # Internals
+
     def __init__(self, base_field, max_length=None, min_length=None,
                  *args, **kwargs):
         self.base_field = base_field
@@ -36,25 +54,29 @@ def __init__(self, base_field, max_length=None, min_length=None,
 
     def prepare_value(self, value):
         if isinstance(value, list):
-            return ",".join(
-                six.text_type(self.base_field.prepare_value(v))
-                for v in value
+            return self.prepare_value_serialize(
+                (six.text_type(self.base_field.prepare_value(v))
+                 for v in value)
             )
         return value
 
     def to_python(self, value):
-        if value and len(value):
-            items = value.split(",")
-        else:
-            items = []
+        items = self.to_python_deserialize(value)
 
         errors = []
         values = []
         for i, item in enumerate(items, start=1):
             if not len(item):
                 errors.append(ValidationError(
-                    self.error_messages['no_double_commas'],
-                    code='no_double_commas',
+                    self.error_messages['items_no_empty'],
+                    code='items_no_empty',
+                ))
+                continue
+
+            if ',' in item:
+                errors.append(ValidationError(
+                    self.error_messages['items_no_commas'],
+                    code='items_no_commas',
                 ))
                 continue
 
@@ -121,7 +143,7 @@ class SimpleSetField(forms.CharField):
     default_error_messages = {
         'item_invalid': _('Item "%(item)s" in the set did not validate: '),
         'item_n_invalid': _('Item %(nth)s in the set did not validate: '),
-        'no_double_commas': _('No leading, trailing, or double commas.'),
+        'items_no_commas': _('No leading, trailing, or double commas.'),
         'no_duplicates': _("Duplicates are not supported. "
                            "'%(item)s' appears twice or more.")
     }
@@ -156,8 +178,8 @@ def to_python(self, value):
         for i, item in enumerate(items, start=1):
             if not len(item):
                 errors.append(ValidationError(
-                    self.error_messages['no_double_commas'],
-                    code='no_double_commas',
+                    self.error_messages['items_no_commas'],
+                    code='items_no_commas',
                 ))
                 continue
 

tests/django_mysql_tests/test_forms.py

@@ -130,6 +130,69 @@ def test_required(self):
         assert excinfo.value.messages[0] == 'This field is required.'
 
 
+class CustomListField(SimpleListField):
+
+    default_error_messages = dict(
+        SimpleListField.default_error_messages,
+        items_no_commas="Commas are not allowed.",
+        items_no_empty="Empty lines are not allowed."
+    )
+
+    def prepare_value_serialize(self, values):
+        return "\n".join(values)
+
+    def to_python_deserialize(self, value):
+        if not value:
+            return []
+        else:
+            return value.splitlines()
+
+
+class CustomListFieldTests(TestCase):
+    """
+    Check that we can subclass SimpleListField and replace how data is
+    converted back and forth from the form easily
+    """
+    def test_valid(self):
+        field = CustomListField(forms.CharField())
+        value = field.clean('a\nb\nc')
+        assert value == ['a', 'b', 'c']
+
+    def test_to_python_no_empties(self):
+        field = CustomListField(forms.IntegerField())
+        with pytest.raises(exceptions.ValidationError) as excinfo:
+            field.clean('\n\n')
+        assert (
+            excinfo.value.messages[0] ==
+            'Empty lines are not allowed.'
+        )
+
+    def test_to_python_no_commas(self):
+        field = CustomListField(forms.IntegerField())
+        with pytest.raises(exceptions.ValidationError) as excinfo:
+            field.clean(',1')
+        assert (
+            excinfo.value.messages[0] ==
+            'Commas are not allowed.'
+        )
+
+    def test_to_python_base_field_does_not_validate(self):
+        field = CustomListField(forms.IntegerField())
+        with pytest.raises(exceptions.ValidationError) as excinfo:
+            field.clean('a\nb\n9')
+        assert (
+            excinfo.value.messages[0] ==
+            'Item 1 in the list did not validate: Enter a whole number.'
+        )
+
+    def test_prepare_value(self):
+        field = CustomListField(forms.CharField())
+        value = field.prepare_value(['a', 'b', 'c'])
+        assert value.split('\n') == ['a', 'b', 'c']
+
+        assert field.prepare_value('1\na') == '1\na'
+
+
 class TestSimpleSetField(TestCase):
 
     def test_valid(self):