Fixed #22959, #23473

docs/ref/validators.txt

@@ -37,6 +37,12 @@ use the same validator with forms::
     class MyForm(forms.Form):
         even_field = forms.IntegerField(validators=[validate_even])
 
+You can also use a class with a ``__call__`` method for configurable or more
+complex validators, similar to the :class:`RegexValidator`. If the validator is
+passed to a model field you should make sure it is :ref:`serializable by the
+migration framework <migration-serializing>` and therefore has a
+:ref:`deconstruct() <custom-deconstruct-method>` and ``__eq__()`` method.
+
 How validators are run
 ======================
 

docs/topics/migrations.txt

@@ -601,6 +601,10 @@ of three things ``(path, args, kwargs)``:
 Django will write out the value as an instantiation of your class with the
 given arguments, similar to the way it writes out references to Django fields.
 
+To prevent infinite migration creation you should also add a ``__eq__()``
+method to the decorated class. This function will be called by Django's
+migration framework to detect changes between states.
+
 As long as all of the arguments to your class' constructor are themselves
 serializable, you can just use the ``@deconstructible`` class decorator
 from ``django.utils.deconstruct`` to add the method::
@@ -611,8 +615,13 @@ from ``django.utils.deconstruct`` to add the method::
     class MyCustomClass(object):
 
         def __init__(self, foo=1):
+            self.foo = foo
             ...
 
+        def __eq__(self, other):
+            return self.foo == other.foo
+
+
 The decorator adds logic to capture and preserve the arguments on their
 way into your constructor, and then returns those arguments exactly when
 deconstruct() is called.