models.CharField shouldn't accept a string as max_length

[Santiago L]

In models.CharField you can define max_length as string and the system check framework doesn't complain (​related mailing list thread):

from django.db import models

class Foo(models.Model):
    bar = models.CharField(max_length='16')

>>> # following code raises an Exception
>>> obj = Foo(bar='lorem ipsum')
>>> obj.clean_fields()
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/usr/local/lib/python3.4/dist-packages/django/db/models/base.py", line 1167, in clean_fields
    setattr(self, f.attname, f.clean(raw_value, self))
  File "/usr/local/lib/python3.4/dist-packages/django/db/models/fields/__init__.py", line 589, in clean
    self.run_validators(value)
  File "/usr/local/lib/python3.4/dist-packages/django/db/models/fields/__init__.py", line 541, in run_validators
    v(value)
  File "/usr/local/lib/python3.4/dist-packages/django/core/validators.py", line 280, in __call__
    if self.compare(cleaned, self.limit_value):
  File "/usr/local/lib/python3.4/dist-packages/django/core/validators.py", line 319, in <lambda>
    compare = lambda self, a, b: a > b
TypeError: unorderable types: int() > str()

[Santiago L]

Related to #20440.

[Alasdair Nicol]

Pull request ​https://github.com/django/django/pull/4676

[Baptiste Mispelon]

Is there a reason why we can't cast max_length to an integer value in Field.__init__?

[Santiago L]

Replying to bmispelon:

Is there a reason why we can't cast max_length to an integer value in Field.__init__?

Because that will mask the real "problem" as has happened with the current implementation that casts mask_length at _check_max_length_attribute .

IMHO, Django shouldn't handle user's fault but warn the user about it.

[Tim Graham <timograham@…>]

In d091b75:

Fixed #24818 -- Prevented models.CharField from accepting a string as max_length