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Fixed #24305 -- Allowed overriding fields on abstract models.

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Fields inherited from abstract base classes may be overridden like
any other Python attribute. Inheriting from multiple models/classes
with the same attribute name will follow the MRO.
This commit is contained in:
Aron Podrigal
2015-08-03 08:03:41 -04:00
committed by Tim Graham
parent 61a16e0270
commit 85ef98dc6e
5 changed files with 443 additions and 33 deletions
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85
django/db/models/base.py
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@@ -212,26 +212,35 @@ class ModelBase(type):
if isinstance(field, OneToOneField):
related = resolve_relation(new_class, field.remote_field.model)
parent_links[make_model_tuple(related)] = field
# Track fields inherited from base models.
inherited_attributes = set()
# Do the appropriate setup for any model parents.
for base in parents:
for base in new_class.mro():
original_base = base
if not hasattr(base, '_meta'):
if base not in parents or not hasattr(base, '_meta'):
# Things without _meta aren't functional models, so they're
# uninteresting parents.
inherited_attributes |= set(base.__dict__.keys())
continue
parent_fields = base._meta.local_fields + base._meta.local_many_to_many
# Check for clashes between locally declared fields and those
# on the base classes (we cannot handle shadowed fields at the
# moment).
for field in parent_fields:
if field.name in field_names:
raise FieldError(
'Local field %r in class %r clashes '
'with field of similar name from '
'base class %r' % (field.name, name, base.__name__)
)
if not base._meta.abstract:
# Check for clashes between locally declared fields and those
# on the base classes.
for field in parent_fields:
if field.name in field_names:
raise FieldError(
'Local field %r in class %r clashes with field of '
'the same name from base class %r.' % (
field.name,
name,
base.__name__,
)
)
else:
inherited_attributes.add(field.name)
# Concrete classes...
base = base._meta.concrete_model
base_key = make_model_tuple(base)
@@ -246,6 +255,18 @@ class ModelBase(type):
auto_created=True,
parent_link=True,
)
if attr_name in field_names:
raise FieldError(
"Auto-generated field '%s' in class %r for "
"parent_link to base class %r clashes with "
"declared field of the same name." % (
attr_name,
name,
base.__name__,
)
)
# Only add the ptr field if it's not already present;
# e.g. migrations will already have it specified
if not hasattr(new_class, attr_name):
@@ -256,16 +277,19 @@ class ModelBase(type):
else:
base_parents = base._meta.parents.copy()
# .. and abstract ones.
# Add fields from abstract base class if it wasn't overridden.
for field in parent_fields:
new_field = copy.deepcopy(field)
new_class.add_to_class(field.name, new_field)
# Replace parent links defined on this base by the new
# field as it will be appropriately resolved if required.
if field.one_to_one:
for parent, parent_link in base_parents.items():
if field == parent_link:
base_parents[parent] = new_field
if (field.name not in field_names and
field.name not in new_class.__dict__ and
field.name not in inherited_attributes):
new_field = copy.deepcopy(field)
new_class.add_to_class(field.name, new_field)
# Replace parent links defined on this base by the new
# field. It will be appropriately resolved if required.
if field.one_to_one:
for parent, parent_link in base_parents.items():
if field == parent_link:
base_parents[parent] = new_field
# Pass any non-abstract parent classes onto child.
new_class._meta.parents.update(base_parents)
@@ -281,13 +305,18 @@ class ModelBase(type):
# Inherit private fields (like GenericForeignKey) from the parent
# class
for field in base._meta.private_fields:
if base._meta.abstract and field.name in field_names:
raise FieldError(
'Local field %r in class %r clashes '
'with field of similar name from '
'abstract base class %r' % (field.name, name, base.__name__)
)
new_class.add_to_class(field.name, copy.deepcopy(field))
if field.name in field_names:
if not base._meta.abstract:
raise FieldError(
'Local field %r in class %r clashes with field of '
'the same name from base class %r.' % (
field.name,
name,
base.__name__,
)
)
else:
new_class.add_to_class(field.name, copy.deepcopy(field))
if abstract:
# Abstract base models can't be instantiated and don't appear in