POST with None data in Request Factory in Django

Question

I'm moving my django application from 1.x to 2.2, When running unit tests, I get a error about posting None as data. Is it allowed to post None in previous versions? Is there any way to post None via RequestFactory?

I don't want to give a empty string, since the field needs to be validated

r = RequestFactory()
rr = r.post("some-url",{"name":"sri", "kd_ratio":None})

Error:

  File "/usr/local/lib/python3.7/site-packages/django/test/client.py", line 354, in post
    post_data = self._encode_data(data, content_type)
  File "/usr/local/lib/python3.7/site-packages/django/test/client.py", line 313, in _encode_data
    return encode_multipart(BOUNDARY, data)
  File "/usr/local/lib/python3.7/site-packages/django/test/client.py", line 197, in encode_multipart
    'Cannot encode None as POST data. Did you mean to pass an '
TypeError: Cannot encode None as POST data. Did you mean to pass an empty string or omit the value?

Subglacial

What is the error that you get? Please attach the stacktrace with the question. – Kalasky

StackTrace has been attached – Subglacial

Use the format='json' argument: r.post('some-url', {'name': 'sri', 'kd_ratio': None}, format='json') – Incredible

Answer 1

https://docs.djangoproject.com/en/4.2/topics/testing/tools/#django.test.Client.post

You need to add content_type="application/json" as an argument to be able to send None/null as a value.

The reason is that the default content type (multipart/form-data) doesn't support null values, only empty strings, hence the suggestion.

Volumeter

Underrated answer that saves lives haha – Cryptic

Truth, Django 4.1 docs are here: docs.djangoproject.com/en/4.1/topics/testing/tools – Lalo

Answer 2

Hopefully this saves some time for someone else

This was my problem in Django 4.1 and Django Rest Framework 3.13.1.
res = self.client.patch("some-url", {"assigned_user": None})

@drew's suggestion did not solve it for me:
res = self.client.patch("some-url", {"assigned_user": None}, content_type="application/json")

Then I read the docs and understood that this works:
res = self.client.patch("some-url", {"assigned_user": ""})

But I didn't like it and luckily I found @Masood Khaari quickly-overread suggestion below the question:
res = self.client.patch("some-url", {"assigned_user": None}), format='json')

Cabanatuan

Answer 3

I'll add my little contribution/observation here.

My view post() method is looking for request.POST.get("action"). Thus I couldn't set the content-type as per the accepted answer, since then that means that all my data is moved to the request.body. I'm not going to re-write all those just so I can test them.

Thus instead, I have set all None value that may be present in the test data sent to the views by an empty string (which is what the browser would actually send a "None" as anyways). In my case, the None value appeared to be fields in the Form that were not present for whatever reason the request.

def build_mock_post_data(form, formsets=[]):
    """ builds the k-v pairs that mimics the POST data sent by client, including managment forms & formsets """
    full_post_data = {}
    for formset in formsets:
        prefix = formset.prefix
        fdata = {}
        for i, f in enumerate(formset.initial_forms):
            for key, val in f.initial.items():                   # create the form field's keys
                fdata[f"{prefix}-{i}-{key}"] = str(val)
            fdata[f"{prefix}-{i}-id"] = str(f.fields["id"].initial )                
        fdata[f"{prefix}-TOTAL_FORMS"] = len(formset.initial_forms)
        fdata[f"{prefix}-INITIAL_FORMS"] = len(formset.initial_forms)               # since for test, we always consider the imported fixtures is whatebver will be tested. caller could update that valeur to simulate "new" dets added
        full_post_data.update(**fdata)

    # add main form data
    full_post_data.update(**form.initial)

    # check for None & replace them by empty strings, otherwise issues with django.Client.post(...)
    nones = [k for k,v in full_post_data.items() if v is None]
    for n in nones:
        full_post_data[n] = ""
    return full_post_data

Then in the tests where I have post data I need to sent:

# prepare post data ...
post_data = build_mock_post_data(form, formsets=[formset])
post_data["action"] = "soumpick"

# TODO: make call
response = self.client.post(reverse('soumission:update_open', args=(ent_soum.id, )), data={**post_data})
r = json.loads(response.content.decode())
log.info(f"Response: {r}")

Sisson

Would you have a piece of code to share? Have tried both the accepted answer and yours but still can't seem to get things working. – Zacheryzack