For ConditionalVersionField get_fields() returns too many fields

src/concurrency/fields.py

@@ -1,6 +1,7 @@
 from __future__ import absolute_import, unicode_literals
 
 import copy
+import functools
 import hashlib
 import logging
 import time
@@ -44,8 +45,8 @@ def class_prepared_concurrency_handler(sender, **kwargs):
 
         if hasattr(sender, 'ConcurrencyMeta'):
             sender._concurrencymeta.enabled = getattr(sender.ConcurrencyMeta, 'enabled', True)
-            check_fields = getattr(sender.ConcurrencyMeta, 'check_fields', [])
-            ignore_fields = getattr(sender.ConcurrencyMeta, 'ignore_fields', [])
+            check_fields = getattr(sender.ConcurrencyMeta, 'check_fields', None)
+            ignore_fields = getattr(sender.ConcurrencyMeta, 'ignore_fields', None)
             if check_fields and ignore_fields:
                 raise ValueError("Cannot set both 'check_fields' and 'ignore_fields'")
 
@@ -310,6 +311,19 @@ def inner(self, force_insert=False, force_update=False, using=None, **kwargs):
         return update_wrapper(inner, func)
 
 
+def filter_fields(instance, field):
+    if not field.concrete:
+        # reverse relation
+        return False
+    if field.is_relation and field.related_model is None:
+        # generic foreignkeys
+        return False
+    if field.many_to_many and instance.pk is None:
+        # can't load remote object yet
+        return False
+    return True
+
+
 class ConditionalVersionField(AutoIncVersionField):
     def contribute_to_class(self, cls, name, virtual_only=False):
         super(ConditionalVersionField, self).contribute_to_class(cls, name, virtual_only)
@@ -333,10 +347,11 @@ def _get_hash(self, instance):
         check_fields = instance._concurrencymeta.check_fields
         ignore_fields = instance._concurrencymeta.ignore_fields
 
+        filter_ = functools.partial(filter_fields, instance)
         if check_fields is None and ignore_fields is None:
-            fields = sorted([f.name for f in instance._meta.get_fields()])
+            fields = sorted([f.name for f in filter(filter_, instance._meta.get_fields())])
         elif check_fields is None:
-            fields = sorted([f.name for f in instance._meta.get_fields()
+            fields = sorted([f.name for f in filter(filter_, instance._meta.get_fields())
                              if f.name not in ignore_fields])
         else:
             fields = instance._concurrencymeta.check_fields

tests/demoapp/demo/migrations/0003_auto_20160224_0637.py

@@ -0,0 +1,27 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('demo', '0002_conditionalversionmodelwithoutmeta'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Anything',
+            fields=[
+                ('id', models.AutoField(primary_key=True, verbose_name='ID', serialize=False, auto_created=True)),
+                ('name', models.CharField(max_length=10)),
+                ('a_relation', models.ForeignKey(to='demo.ConditionalVersionModelWithoutMeta')),
+            ],
+        ),
+        migrations.AddField(
+            model_name='conditionalversionmodelwithoutmeta',
+            name='anythings',
+            field=models.ManyToManyField(to='demo.Anything'),
+        ),
+    ]

tests/demoapp/demo/models.py

@@ -12,6 +12,7 @@
            'ProxyModel', 'InheritedModel', 'CustomSaveModel',
            'ConcreteModel', 'TriggerConcurrentModel',
            'ConditionalVersionModelWithoutMeta',
+           'Anything',
            ]
 
 
@@ -213,6 +214,15 @@ class ConcurrencyMeta:
         check_fields = ['field1', 'field2', 'user']
 
 
+class Anything(models.Model):
+    """
+    Will create a ManyToOneRel automatic field on
+    ConditionalVersionModelWithoutMeta instances.
+    """
+    name = models.CharField(max_length=10)
+    a_relation = models.ForeignKey('demo.ConditionalVersionModelWithoutMeta')
+
+
 class ConditionalVersionModelWithoutMeta(models.Model):
     """
     This model doesn't have ConcurrencyMeta defined.
@@ -222,6 +232,7 @@ class ConditionalVersionModelWithoutMeta(models.Model):
     field2 = models.CharField(max_length=30, blank=True, null=True, unique=True)
     field3 = models.CharField(max_length=30, blank=True, null=True, unique=True)
     user = models.ForeignKey(User, null=True)
+    anythings = models.ManyToManyField(Anything)
 
     class Meta:
         app_label = 'demo'