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from functools import partial
from django.db import models
from django.db.models.fields.related import (
RECURSIVE_RELATIONSHIP_CONSTANT,
ManyToManyDescriptor,
RelatedField,
create_many_to_many_intermediary_model,
)
class CustomManyToManyField(RelatedField):
"""
Ticket #24104 - Need to have a custom ManyToManyField,
which is not an inheritor of ManyToManyField.
"""
many_to_many = True
def __init__(
self,
to,
db_constraint=True,
swappable=True,
related_name=None,
related_query_name=None,
limit_choices_to=None,
symmetrical=None,
through=None,
through_fields=None,
db_table=None,
**kwargs,
):
try:
to._meta
except AttributeError:
to = str(to)
kwargs["rel"] = models.ManyToManyRel(
self,
to,
related_name=related_name,
related_query_name=related_query_name,
limit_choices_to=limit_choices_to,
symmetrical=symmetrical
if symmetrical is not None
else (to == RECURSIVE_RELATIONSHIP_CONSTANT),
through=through,
through_fields=through_fields,
db_constraint=db_constraint,
)
self.swappable = swappable
self.db_table = db_table
if kwargs["rel"].through is not None and self.db_table is not None:
raise ValueError(
"Cannot specify a db_table if an intermediary model is used."
)
super().__init__(
related_name=related_name,
related_query_name=related_query_name,
limit_choices_to=limit_choices_to,
**kwargs,
)
def contribute_to_class(self, cls, name, **kwargs):
if self.remote_field.symmetrical and (
self.remote_field.model == "self"
or self.remote_field.model == cls._meta.object_name
):
self.remote_field.related_name = "%s_rel_+" % name
super().contribute_to_class(cls, name, **kwargs)
if (
not self.remote_field.through
and not cls._meta.abstract
and not cls._meta.swapped
):
self.remote_field.through = create_many_to_many_intermediary_model(
self, cls
)
setattr(cls, self.name, ManyToManyDescriptor(self.remote_field))
self.m2m_db_table = partial(self._get_m2m_db_table, cls._meta)
def get_internal_type(self):
return "ManyToManyField"
# Copy those methods from ManyToManyField because they don't call super() internally
contribute_to_related_class = models.ManyToManyField.__dict__[
"contribute_to_related_class"
]
_get_m2m_attr = models.ManyToManyField.__dict__["_get_m2m_attr"]
_get_m2m_reverse_attr = models.ManyToManyField.__dict__["_get_m2m_reverse_attr"]
_get_m2m_db_table = models.ManyToManyField.__dict__["_get_m2m_db_table"]
class InheritedManyToManyField(models.ManyToManyField):
pass
class MediumBlobField(models.BinaryField):
"""
A MySQL BinaryField that uses a different blob size.
"""
def db_type(self, connection):
return "MEDIUMBLOB"
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