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Opened 12 months ago

Last modified 5 weeks ago

#20744 new Bug

Docs imply that forms.Field.__init__ accepts any keyword arguments

Reported by: gthb Owned by: nobody
Component: Documentation Version: master
Severity: Normal Keywords:
Cc: Pashkin Triage Stage: Accepted
Has patch: no Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description

At https://docs.djangoproject.com/en/dev/ref/forms/fields/ there is this:

class Field(**kwargs)

with no stated constraints on kwargs, thus implying (incorrectly) that any keyword argument can safely be passed to the forms.Field constructor.

That leads to code which worked in previous Django versions but regresses in the current version. The case I have in mind is in django-authority's admin.py where the kwargs passed to formfield_callback (which can include request) are passed on to Field.formfield, whose documentation says “All of the kwargs dictionary is passed directly to the form field’s __init__() method” ... and that __init__ method can't include request. So upgrading Django yields this somewhat tricky-to-troubleshoot error in a django-authority admin action:

TypeError: __init__() got an unexpected keyword argument 'request'

  ...
  File "django/forms/models.py", line 170, in fields_for_model
    formfield = formfield_callback(f, **kwargs)
  File "authority/admin.py", line 33, in formfield_for_dbfield
    return db_field.formfield(**kwargs)
  File "django/db/models/fields/__init__.py", line 646, in formfield
    return super(CharField, self).formfield(**defaults)
  File "django/db/models/fields/__init__.py", line 499, in formfield
    return form_class(**defaults)
  File "django/forms/fields.py", line 188, in __init__
    super(CharField, self).__init__(*args, **kwargs)

At some point in this chain, the request keyword argument must be popped out. Presumably directly before the call to Field.formfield. In any case, this requirement should be documented.

(Or forms.Field.__init__ could be changed to tolerate and ignore unknown keyword arguments. But that's a riskier change.)

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Change History (2)

comment:1 Changed 12 months ago by timo

  • Needs documentation unset
  • Needs tests unset
  • Patch needs improvement unset
  • Triage Stage changed from Unreviewed to Accepted

comment:2 Changed 5 weeks ago by Pashkin

  • Cc Pashkin added

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