Unable to nullify choice fields via the API

[fantasmita]

Environment

• Python version: 3.6.5
• NetBox version: 2.7.3

To fully unrack a device, you must blank out its rack, position, and face values.
The face field has a non-null constraint and has an API validator that requires its value to be either front or rear, so it's not possible to blank out the value through the API which prevents the device from being removed from the rack.

Steps to Reproduce

1. Create a device in netbox with values for rack, position, and face.
2. Try to clear all three values with a PATCH like the following

curl -X PATCH "https://$NETBOX/api/dcim/devices/$ID/" -H  "accept: application/json" -H  "Content-Type: application/json" -H  "X-CSRFToken: $TOKEN" -d "{  \"rack\": null,  \"position\": null,  \"face\": \"\"}"

Expected Behavior

The device to be unracked

Observed Behavior

{
  "face": [
    " is not a valid choice."
  ]
}

If passing null for the face value, the django non-null constraint is hit.
If patching just the rack and position values without touching the face, the Cannot select a rack face without assigning a rack. validator is hit.

[jeremystretch]

Omit the face field if you are unracking a device: It will be nullified automatically. The following request is successful:

curl -X PATCH http://localhost:8000/api/dcim/devices/<ID>/ \
-H "Authorization: Token <TOKEN>" \
-H "Content-Type: application/json" \
-H "Accept: application/json; indent=4" \
-d '{"rack": null, "position": null}'

[fantasmita]

Thanks for looking and for the suggestions.
However, I don't think the nullification is working as expected.

I know netboxdemo.com is unsanctioned, but here's a quick reproducible illustration of the problem in that environment when following your suggestions.

setting face to the empty string:

$ curl -X PATCH "https://netboxdemo.com/api/dcim/devices/1/" \
>     -H "Authorization: Token  72830d67beff4ae178b94d8f781842408df8069d" \
>     -H "Content-Type: application/json" \
>     -H "Accept: application/json; indent=4" \
>     -d '{"rack": null, "position": null, "face": ""}'
{
    "face": [
        " is not a valid choice."
    ]
}

omitting face:

$ curl -X PATCH "https://netboxdemo.com/api/dcim/devices/1/" \
>     -H "Authorization: Token  72830d67beff4ae178b94d8f781842408df8069d" \
>     -H "Content-Type: application/json" \
>     -H "Accept: application/json; indent=4" \
>     -d '{"rack": null, "position": null}'
{
    "face": [
        "Cannot select a rack face without assigning a rack."
    ]
}

[jeremystretch]

Sorry, I had pasted the wrong command in my previous comment. I've corrected it to omit the face field. This is working on v2.7.4.

[fantasmita]

No worries, thanks.

I'm sorry for not explaining myself more clearly, but omitting the face when making a PATCH request doesn't successfully nullify the value before it hits the site / rack validators, which results in the Cannot select a rack face without assigning a rack. validation error I pasted above.
I confirmed today that this still occurs on a fresh installation of v2.7.4.

Anyway, I'm happy to work around this and it's definitely possible I'm missing something, but let me know if you have other thoughts or if I can provide any other information. Thanks again for your time

[jeremystretch]

Sorry, this took a while to track down. I wasn't able to replicate the error earlier because the device that I was testing against did not have a rack face already assigned, so the validation check was not being triggered.