django from_form does not work with filefields

[arjoonn-s]

The from_form function does not bind files correctly.

From the source available I think it should be supplying file fields separately. Currently it is running:

    return _forms_impl(
        st.builds(
            partial(form, **form_kwargs),  # type: ignore
            data=st.fixed_dictionaries(field_strategies),  # type: ignore
        )
    )

I think it should have been something like:

    return _forms_impl(
        st.builds(
            partial(form, **form_kwargs),  # type: ignore
            data=st.fixed_dictionaries(field_strategies),  # type: ignore
            files=st.fixed_dictionaries(field_strategies),  # type: ignore
        )
    )

cc @sethuvishal

---

Is this expected? If not I think we're happy to submit a patch for this.

[Zac-HD]

Hmm, unfortunately none of Hypothesis' regular contributors are Django users, so it's pretty plausible that we've missed an upstream change or something like that. I'd be happy to accept a patch, but would appreciate more-detailed-than-usual notes pointing to Django docs etc to explain what's going on 🙂

[arjoonn-s]

More than happy to help! Hypo has been of great use to us in testing our django codebase.

1. We mainly use hypo with django forms so I'll only talk about that.
2. The forms are initialized as form = MyForm(data=request.POST, files=request.FILES) ref
3. After this we can do form.is_valid() to check if the form is valid.

The problem arises when we have FileField in the form for handling file uploads.

1. Hypo generates file data correctly, but does not pass it to the form class correctly as seen in the source.
2. Since the file field is passed as data, the content of the file never reaches the django form.
3. This causes it to treat the file as an empty file and so fail validation where we have added rules for ensuring that file should be non-empty.

The expected code would be to have the hypo code in the referred section as:

return _forms_impl(
        st.builds(
            partial(form, **form_kwargs),  # type: ignore
            data=st.fixed_dictionaries(non_file_field_strategies),  # type: ignore
            files=st.fixed_dictionaries(file_field_strategies),  # type: ignore
        )
    )

thus passing the strategies correctly to the form builder.

Does that make more sense? I'm happy to answer any other questions.

[Zac-HD]

Sounds great!