id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
30610	Model.full_clean() doesn't prevetn invalid (null) values when blank=True.	Keryn Knight	nobody	"Consider the following model definition (ignoring the merits of it):
{{{
class Example(models.Model):
    txt = models.TextField(blank=True, null=False)
}}}
I'd expect to be able to do:
{{{
x = Example(txt=None)
x.full_clean()
}}}
which should raise a `ValidationError` because None is **explicitly** not a valid value for the field (`null=False`) - but it doesn't, so subsequently doing `x.save()` will raise `IntegrityError` when the database (sqlite3, postgresql, I'd assume the same for mysql/mariadb) attempts to do the insert, with something like:
{{{IntegrityError: NOT NULL constraint failed: testing_example.txt}}} (sqlite)
{{{IntegrityError: null value in column ""txt"" violates not-null constraint}}} (postgresql)

I think it's down to
* if `blank=True` then `Model.clean_fields()` short circuits because `EMPTY_VALUES` includes `None` 
* if `blank=False` it doesn't short-circuit and instead falls into `Field.validate()` where the null check happens **before** the blank check, so the ValidationError is correctly raised that `This field cannot be null`

Tested against master @ 54dcfbc36780054d39299bfd1078938e5dd4e839, encountered in staging environment in 1.11, but it looks like it goes back to at least 2010 (commit 2f9853b2dc90f30317e0374396f08e3d142844d2)

There is this comment before bailing out early:
{{{
# Skip validation for empty fields with blank=True. The developer
# is responsible for making sure they have a valid value.
}}}
This is specious reasoning. Blank is not so super-special that it should deserve throwing actual validation out of the window and into the mental gymnastics necessary to decide whether or not you can actually try and save something that ostensibly ''passed'' validation, according to both the code and the intent therein."	Cleanup/optimization	closed	Database layer (models, ORM)	dev	Normal	duplicate			Unreviewed	0	0	0	0	0	0