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Fixed #25160 -- Moved unsaved model instance data loss check to Model.save()

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This mostly reverts 5643a3b51b and
81e1a35c36.

Thanks Carl Meyer for review.
This commit is contained in:
Tim Graham 2015-07-24 07:51:40 -04:00
parent 12f91f6ebd
commit 5980b05c1f
15 changed files with 106 additions and 198 deletions
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30
docs/ref/models/fields.txt
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@ -1383,30 +1383,6 @@ The possible values for :attr:`~ForeignKey.on_delete` are found in
If in doubt, leave it to its default of ``True``.
.. attribute:: ForeignKey.allow_unsaved_instance_assignment
.. versionadded:: 1.8
This flag was added for backwards compatibility as older versions of
Django always allowed assigning unsaved model instances.
Django prevents unsaved model instances from being assigned to a
``ForeignKey`` field to prevent accidental data loss (unsaved foreign keys
are silently ignored when saving a model instance).
If you require allowing the assignment of unsaved instances and aren't
concerned about the data loss possibility (e.g. you never save the objects
to the database), you can disable this check by creating a subclass of the
field class and setting its ``allow_unsaved_instance_assignment`` attribute
to ``True``. For example::
class UnsavedForeignKey(models.ForeignKey):
# A ForeignKey which can point to an unsaved object
allow_unsaved_instance_assignment = True
class Book(models.Model):
author = UnsavedForeignKey(Author, on_delete=models.CASCADE)
.. _ref-manytomany:
``ManyToManyField``
@ -1607,12 +1583,6 @@ that control how the relationship functions.
If in doubt, leave it to its default of ``True``.
.. attribute:: ManyToManyField.allow_unsaved_instance_assignment
.. versionadded:: 1.8
Works analogously to :attr:`ForeignKey.allow_unsaved_instance_assignment`.
:class:`ManyToManyField` does not support :attr:`~Field.validators`.
:attr:`~Field.null` has no effect since there is no way to require a