SplitDateTime widget crashes while processing initials

[Михаил Акопян]

I have a model with DateTime field. I want to set initials for this field in django admin by using query params. For example:

# models.py

class MyModel(models.Model):
    created_at = models.DateTimeField()


# admin.py

@admin.register(MyModel)
class MyModelAdmin(admin.ModelAdmin):
    pass

Trying to create new object of MyModel with initial for created_at field:
http://127.0.0.1:8000/admin/myapp/mymodel/add/?created_at=2024-10-10%2005%3A57%3A31

Admin sites crashes with 500 error. This happens because the method decompress of the SplitDateTimeWidget expects an object of datetime type, but it is passed the string instead.

Proposed fix:

    def decompress(self, value):
        if isinstance(value, str):
            try:
                value = datetime.fromisoformat(value)
            except ValueError:
                return [None, None]
        if value:
            value = to_current_timezone(value)
            return [value.date(), value.time()]
        return [None, None]