Refs #12203 -- Improved error handling for the case where a user manually specifies an m2m field with an explicit through field. Thanks to dgouldin for the report, and Ramiro Morales for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@11737 bcc190cf-cafb-0310-a4f2-bffc1f526a37

2 files changed, 16 insertions, 2 deletions

diff --git a/django/contrib/admin/validation.py b/django/contrib/admin/validation.py
index 05e5c6d300..d1f8de24e6 100644
--- a/django/contrib/admin/validation.py
+++ b/django/contrib/admin/validation.py
@@ -149,7 +149,7 @@ def validate(cls, model):
             validate_inline(inline, cls, model)
 
 def validate_inline(cls, parent, parent_model):
-    
+
     # model is already verified to exist and be a Model
     if cls.fk_name: # default value is None
         f = get_field(cls, cls.model, cls.model._meta, 'fk_name', cls.fk_name)
@@ -196,6 +196,9 @@ def validate_base(cls, model):
         check_isseq(cls, 'fields', cls.fields)
         for field in cls.fields:
             check_formfield(cls, model, opts, 'fields', field)
+            f = get_field(cls, model, opts, 'fields', field)
+            if isinstance(f, models.ManyToManyField) and not f.rel.through._meta.auto_created:
+                raise ImproperlyConfigured("'%s.fields' can't include the ManyToManyField field '%s' because '%s' manually specifies a 'through' model." % (cls.__name__, field, field))
         if cls.fieldsets:
             raise ImproperlyConfigured('Both fieldsets and fields are specified in %s.' % cls.__name__)
         if len(cls.fields) > len(set(cls.fields)):
diff --git a/tests/regressiontests/admin_validation/models.py b/tests/regressiontests/admin_validation/models.py
index 93e3e065e6..924cf69d4d 100644
--- a/tests/regressiontests/admin_validation/models.py
+++ b/tests/regressiontests/admin_validation/models.py
@@ -108,7 +108,18 @@ Exception: <class 'regressiontests.admin_validation.models.TwoAlbumFKAndAnE'> ha
 
 >>> validate_inline(TwoAlbumFKAndAnEInline, None, Album)
 
-# Regression test for #12203 -- If the explicitly provided through model
+# Regression test for #12203 - Fail more gracefully when a M2M field that
+# specifies the 'through' option is included in the 'fields' ModelAdmin option.
+
+>>> class BookAdmin(admin.ModelAdmin):
+...     fields = ['authors']
+
+>>> validate(BookAdmin, Book)
+Traceback (most recent call last):
+    ...
+ImproperlyConfigured: 'BookAdmin.fields' can't include the ManyToManyField field 'authors' because 'authors' manually specifies a 'through' model.
+
+# Regression test for #12209 -- If the explicitly provided through model
 # is specified as a string, the admin should still be able use
 # Model.m2m_field.through