Fix callable default usage in admin forms

localized_fields/fields/field.py

@@ -11,6 +11,27 @@ from ..forms import LocalizedFieldForm
 from ..value import LocalizedValue
 
 
+class FormClassFactory:
+    """When mixing callables as defaults and localized fields, Django will
+    render the default language value in the input form of the admin interface,
+    causing the printed hidden value to be diff-ed with the value provided in
+    the form, instead of a real instance of LocalizedField."""
+
+    def __init__(self, form_class):
+        self.form_class = form_class
+
+    def produce(self, **kwargs):
+        """Remove the parameter which triggers the issue.
+
+        Django should be able to determine the initial value without
+        printing it. That's how it worked before without any problems
+        """
+        if kwargs.get("show_hidden_initial"):
+            del kwargs["show_hidden_initial"]
+
+        return self.form_class(**kwargs)
+
+
 class LocalizedField(HStoreField):
     """A field that has the same value in multiple languages.
 
@@ -220,7 +241,7 @@ class LocalizedField(HStoreField):
         """Gets the form field associated with this field."""
 
         defaults = dict(
-            form_class=LocalizedFieldForm,
+            form_class=FormClassFactory(LocalizedFieldForm).produce,
             required=False if self.blank else self.required,
         )
         defaults.update(kwargs)