Fixed #10785 -- Corrected a case for foreign key lookup where the related object is a custom primary key. Thanks to Alex Gaynor for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10952 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/fields/related.py

@@ -132,7 +132,8 @@ class RelatedField(object):
                     v, field = getattr(v, v._meta.pk.name), v._meta.pk
             except AttributeError:
                 pass
-            if field:
+            if not field:
+                field = self.rel.get_related_field()
             if lookup_type in ('range', 'in'):
                 v = [v]
             v = field.get_db_prep_lookup(lookup_type, v)
@@ -958,4 +959,3 @@ class ManyToManyField(RelatedField, Field):
         # A ManyToManyField is not represented by a single column,
         # so return None.
         return None
-

tests/modeltests/custom_pk/fields.py

@@ -0,0 +1,54 @@
+import random
+import string
+
+from django.db import models
+
+class MyWrapper(object):
+    def __init__(self, value):
+        self.value = value
+
+    def __repr__(self):
+        return "<%s: %s>" % (self.__class__.__name__, self.value)
+
+    def __unicode__(self):
+        return self.value
+
+    def __eq__(self, other):
+        if isinstance(other, self.__class__):
+            return self.value == other.value
+        return self.value == other
+
+class MyAutoField(models.CharField):
+    __metaclass__ = models.SubfieldBase
+
+    def __init__(self, *args, **kwargs):
+        kwargs['max_length'] = 10
+        super(MyAutoField, self).__init__(*args, **kwargs)
+
+    def pre_save(self, instance, add):
+        value = getattr(instance, self.attname, None)
+        if not value:
+            value = MyWrapper(''.join(random.sample(string.lowercase, 10)))
+            setattr(instance, self.attname, value)
+        return value
+
+    def to_python(self, value):
+        if not value:
+            return
+        if not isinstance(value, MyWrapper):
+            value = MyWrapper(value)
+        return value
+
+    def get_db_prep_save(self, value):
+        if not value:
+            return
+        if isinstance(value, MyWrapper):
+            return unicode(value)
+        return value
+
+    def get_db_prep_value(self, value):
+        if not value:
+            return
+        if isinstance(value, MyWrapper):
+            return unicode(value)
+        return value

tests/modeltests/custom_pk/models.py

@@ -9,6 +9,8 @@ this behavior by explicitly adding ``primary_key=True`` to a field.
 from django.conf import settings
 from django.db import models, transaction, IntegrityError
 
+from fields import MyAutoField
+
 class Employee(models.Model):
     employee_code = models.IntegerField(primary_key=True, db_column = 'code')
     first_name = models.CharField(max_length=20)
@@ -28,6 +30,16 @@ class Business(models.Model):
     def __unicode__(self):
         return self.name
 
+class Bar(models.Model):
+    id = MyAutoField(primary_key=True, db_index=True)
+
+    def __unicode__(self):
+        return repr(self.pk)
+
+
+class Foo(models.Model):
+    bar = models.ForeignKey(Bar)
+
 __test__ = {'API_TESTS':"""
 >>> dan = Employee(employee_code=123, first_name='Dan', last_name='Jones')
 >>> dan.save()
@@ -121,6 +133,21 @@ DoesNotExist: Employee matching query does not exist.
 ...        print "Fail with %s" % type(e)
 Pass
 
+# Regression for #10785 -- Custom fields can be used for primary keys.
+>>> new_bar = Bar.objects.create()
+>>> new_foo = Foo.objects.create(bar=new_bar)
+>>> f = Foo.objects.get(bar=new_bar.pk)
+>>> f == new_foo
+True
+>>> f.bar == new_bar
+True
+
+>>> f = Foo.objects.get(bar=new_bar)
+>>> f == new_foo
+True
+>>> f.bar == new_bar
+True
+
 """}
 
 # SQLite lets objects be saved with an empty primary key, even though an