Fixed #24289 -- Reversed usage of Field.many_to_one and one_to_many.

Thanks Carl Meyer and Tim Graham for the reviews and to all involved
in the discussion.

5 files changed, 13 insertions, 13 deletions

diff --git a/django/contrib/admin/utils.py b/django/contrib/admin/utils.py
index 00d8b41129..5de0f09a48 100644
--- a/django/contrib/admin/utils.py
+++ b/django/contrib/admin/utils.py
@@ -296,7 +296,7 @@ def _get_non_gfk_field(opts, name):
     "not found" by get_field(). This could likely be cleaned up.
     """
     field = opts.get_field(name)
-    if field.is_relation and field.one_to_many and not field.related_model:
+    if field.is_relation and field.many_to_one and not field.related_model:
         raise FieldDoesNotExist()
     return field
 
diff --git a/django/contrib/contenttypes/fields.py b/django/contrib/contenttypes/fields.py
index c11d6284c0..f47a5165ec 100644
--- a/django/contrib/contenttypes/fields.py
+++ b/django/contrib/contenttypes/fields.py
@@ -27,8 +27,8 @@ class GenericForeignKey(object):
 
     is_relation = True
     many_to_many = False
-    many_to_one = False
-    one_to_many = True
+    many_to_one = True
+    one_to_many = False
     one_to_one = False
     related_model = None
 
@@ -269,8 +269,8 @@ class GenericRelation(ForeignObject):
     auto_created = False
 
     many_to_many = False
-    many_to_one = True
-    one_to_many = False
+    many_to_one = False
+    one_to_many = True
     one_to_one = False
 
     rel_class = GenericRel
diff --git a/django/db/models/deletion.py b/django/db/models/deletion.py
index 431b15b0ef..02b8cf3c27 100644
--- a/django/db/models/deletion.py
+++ b/django/db/models/deletion.py
@@ -65,7 +65,7 @@ def get_candidate_relations_to_delete(opts):
     # N-N  (i.e., many-to-many) relations aren't candidates for deletion.
     return (
         f for f in candidate_model_fields
-        if f.auto_created and not f.concrete and (f.one_to_one or f.many_to_one)
+        if f.auto_created and not f.concrete and (f.one_to_one or f.one_to_many)
     )
 
 
diff --git a/django/db/models/fields/related.py b/django/db/models/fields/related.py
index c991945217..3ded406a6b 100644
--- a/django/db/models/fields/related.py
+++ b/django/db/models/fields/related.py
@@ -1528,8 +1528,8 @@ class ManyToManyRel(ForeignObjectRel):
 class ForeignObject(RelatedField):
     # Field flags
     many_to_many = False
-    many_to_one = False
-    one_to_many = True
+    many_to_one = True
+    one_to_many = False
     one_to_one = False
 
     requires_unique_target = True
@@ -1841,8 +1841,8 @@ class ForeignObject(RelatedField):
 class ForeignKey(ForeignObject):
     # Field flags
     many_to_many = False
-    many_to_one = False
-    one_to_many = True
+    many_to_one = True
+    one_to_many = False
     one_to_one = False
 
     rel_class = ManyToOneRel
diff --git a/django/db/models/options.py b/django/db/models/options.py
index 0b669de121..8920b5d86c 100644
--- a/django/db/models/options.py
+++ b/django/db/models/options.py
@@ -388,9 +388,9 @@ class Options(object):
         # and all the models may not have been loaded yet; we don't want to cache
         # the string reference to the related_model.
         is_not_an_m2m_field = lambda f: not (f.is_relation and f.many_to_many)
-        is_not_a_generic_relation = lambda f: not (f.is_relation and f.many_to_one)
+        is_not_a_generic_relation = lambda f: not (f.is_relation and f.one_to_many)
         is_not_a_generic_foreign_key = lambda f: not (
-            f.is_relation and f.one_to_many and not (hasattr(f.rel, 'to') and f.rel.to)
+            f.is_relation and f.many_to_one and not (hasattr(f.rel, 'to') and f.rel.to)
         )
         return make_immutable_fields_list(
             "fields",
@@ -564,7 +564,7 @@ class Options(object):
         for field in fields:
             # For backwards compatibility GenericForeignKey should not be
             # included in the results.
-            if field.is_relation and field.one_to_many and field.related_model is None:
+            if field.is_relation and field.many_to_one and field.related_model is None:
                 continue
 
             names.add(field.name)