[1.3.X] Fixed #16299 -- Ensure that unicode strings can be used to id…

…entify classes in ForeignKey and ManyToManyFields. Unicode strings aren't actually legal as class names, but this is an issue if you use from __future__ import unicode_literals in your models.py file. Thanks to Martijn Bastiaan for the report, and Anthony Briggs for the final patch.

Backport of r16663 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.3.X@16675 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/options.py

@@ -390,7 +390,7 @@ def _fill_related_objects_cache(self):
                     cache[obj] = model
         for klass in get_models(include_auto_created=True):
             for f in klass._meta.local_fields:
-                if f.rel and not isinstance(f.rel.to, str) and self == f.rel.to._meta:
+                if f.rel and not isinstance(f.rel.to, basestring) and self == f.rel.to._meta:
                     cache[RelatedObject(f.rel.to, klass, f)] = None
         self._related_objects_cache = cache
 
@@ -427,7 +427,7 @@ def _fill_related_many_to_many_cache(self):
                     cache[obj] = model
         for klass in get_models():
             for f in klass._meta.local_many_to_many:
-                if f.rel and not isinstance(f.rel.to, str) and self == f.rel.to._meta:
+                if f.rel and not isinstance(f.rel.to, basestring) and self == f.rel.to._meta:
                     cache[RelatedObject(f.rel.to, klass, f)] = None
         if app_cache_ready():
             self._related_many_to_many_cache = cache

tests/modeltests/invalid_models/invalid_models/models.py

@@ -1,3 +1,4 @@
+#encoding=utf-8
 """
 26. Invalid models
 
@@ -218,6 +219,16 @@ class InvalidSetNull(models.Model):
 class InvalidSetDefault(models.Model):
     fk = models.ForeignKey('self', on_delete=models.SET_DEFAULT)
 
+class UnicodeForeignKeys(models.Model):
+    """Foreign keys which can translate to ascii should be OK, but fail if they're not."""
+    good = models.ForeignKey(u'FKTarget')
+    also_good = models.ManyToManyField(u'FKTarget', related_name='unicode2')
+
+    # In Python 3 this should become legal, but currently causes unicode errors
+    # when adding the errors in core/management/validation.py
+    #bad = models.ForeignKey(u'★')
+
+
 model_errors = """invalid_models.fielderrors: "charfield": CharFields require a "max_length" attribute that is a positive integer.
 invalid_models.fielderrors: "charfield2": CharFields require a "max_length" attribute that is a positive integer.
 invalid_models.fielderrors: "charfield3": CharFields require a "max_length" attribute that is a positive integer.