Fiexed #3055 -- Validate that models target of a GenericRelation have a GenericForeignKey field.

Thanks jason for diagnosing the problem and Marcos Moyano for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14563 bcc190cf-cafb-0310-a4f2-bffc1f526a37

3 files changed, 35 insertions, 0 deletions

diff --git a/django/core/management/validation.py b/django/core/management/validation.py
index 6baa189736..f78fa87b33 100644
--- a/django/core/management/validation.py
+++ b/django/core/management/validation.py
@@ -1,7 +1,14 @@
 import sys
+
+from django.contrib.contenttypes.generic import GenericForeignKey, GenericRelation
 from django.core.management.color import color_style
 from django.utils.itercompat import is_iterable
 
+try:
+    any
+except NameError:
+    from django.utils.itercompat import any
+
 class ModelErrorCollection:
     def __init__(self, outfile=sys.stdout):
         self.errors = []
@@ -224,6 +231,12 @@ def get_validation_errors(outfile, app=None):
                 e.add(opts, "'%s' specifies an m2m relation through model %s, "
                     "which has not been installed" % (f.name, f.rel.through)
                 )
+            elif isinstance(f, GenericRelation):
+                if not any([isinstance(vfield, GenericForeignKey) for vfield in f.rel.to._meta.virtual_fields]):
+                    e.add(opts, "Model '%s' must have a GenericForeignKey in "
+                        "order to create a GenericRelation that points to it."
+                        % f.rel.to.__name__
+                    )
 
             rel_opts = f.rel.to._meta
             rel_name = RelatedObject(f.rel.to, cls, f).get_accessor_name()
diff --git a/django/utils/itercompat.py b/django/utils/itercompat.py
index ab27c3ee01..d4ff2503c7 100644
--- a/django/utils/itercompat.py
+++ b/django/utils/itercompat.py
@@ -37,3 +37,9 @@ def all(iterable):
         if not item:
             return False
     return True
+
+def any(iterable):
+    for item in iterable:
+        if item:
+            return True
+    return False
diff --git a/tests/modeltests/invalid_models/models.py b/tests/modeltests/invalid_models/models.py
index 6e2b579a33..2788aa077e 100644
--- a/tests/modeltests/invalid_models/models.py
+++ b/tests/modeltests/invalid_models/models.py
@@ -4,6 +4,7 @@
 This example exists purely to point out errors in models.
 """
 
+from django.contrib.contenttypes import generic
 from django.db import models
 
 class FieldErrors(models.Model):
@@ -216,6 +217,20 @@ class InvalidSetNull(models.Model):
 class InvalidSetDefault(models.Model):
     fk = models.ForeignKey('self', on_delete=models.SET_DEFAULT)
 
+class Tag(models.Model):
+   name = models.CharField("name", max_length=20)
+
+class TaggedObject(models.Model):
+   object_id = models.PositiveIntegerField("Object ID")
+   tag = models.ForeignKey(Tag)
+   content_object = generic.GenericForeignKey()
+
+class UserTaggedObject(models.Model):
+   object_tag = models.ForeignKey(TaggedObject)
+
+class ArticleAttachment(models.Model):
+   tags = generic.GenericRelation(TaggedObject)
+   user_tags = generic.GenericRelation(UserTaggedObject)
 
 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.
@@ -324,4 +339,5 @@ invalid_models.nonuniquefktarget2: Field 'bad' under model 'FKTarget' must have
 invalid_models.nonexistingorderingwithsingleunderscore: "ordering" refers to "does_not_exist", a field that doesn't exist.
 invalid_models.invalidsetnull: 'fk' specifies on_delete=SET_NULL, but cannot be null.
 invalid_models.invalidsetdefault: 'fk' specifies on_delete=SET_DEFAULT, but has no default value.
+invalid_models.articleattachment: Model 'UserTaggedObject' must have a GenericForeignKey in order to create a GenericRelation that points to it.
 """