DateField.input_formats cannot be printed

[stefan6419846]

I am trying to display the input formats for django.forms.fields.DateField. This seems to fail at the moment when using __str__, while __repr__ works.

Example code:

from django.forms.fields import DateField


print(repr(DateField().input_formats))
print(DateField().input_formats)

This will result in the following error:

Traceback (most recent call last):
  File "<console>", line 1, in <module>
TypeError: __str__ returned non-string (type list)

I would have expected the string representation to be available as well instead of failing with an internal Python error.

[David Sanders]

Hi, thanks for the report!

Interesting:

> lazy_val = lazy(get_format, str, list, tuple)("DATE_INPUT_FORMATS")
> lazy_val.__str__()
['%Y-%m-%d', '%m/%d/%Y', '%m/%d/%y', '%b %d %Y', '%b %d, %Y', '%d %b %Y', '%d %b, %Y', '%B %d %Y', '%B %d, %Y', '%d %B %Y', '%d %B, %Y']
> str(lazy_val)
*** TypeError: __str__ returned non-string (type list)
> type(lazy_val.__str__())
<class 'list'>

Confirmed __str__() is returning a list.

[David Sanders]

PR: ​https://github.com/django/django/pull/16701

[Mariusz Felisiak]

​Alternative PR.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 066aabc:

Fixed #34445 -- Fixed string-casting of non-string lazy objects.

This removes text_cast() as it's the same as cast().
_delegate_bytes and delegate_text are mutually exclusive so the
if self._delegate_bytes branch in cast() is unreachable.

Co-Authored-By: David Sanders <shang.xiao.sanders@…>

[Mariusz Felisiak <felisiak.mariusz@…>]

In f5817c2:

Refs #34445 -- Fixed string-casting of non-string lazy objects when value may be bytes.

If the result type is bytes, then calling bytes() on it does nothing.

If the result type is not bytes, we should not cast to bytes, just
because the return value may be bytes.