ModelMultipleChoiceField does not honor to_field_name at render

[drepo]

Steps to reproduce:

1) Clone the repo (sample Django project which reproduces the bug) at ​https://github.com/drepo/model-multi-render

2) Install requirements.txt (preferably in a virtualenv)

3) Run the migrations

4) ./manage.py loaddata --app demo initial_data.json (Load fixtures -- sample data)

5) Visit ​http://localhost:8000/demo-working/1 -- Notice all items in contents are selected. This is expected.

6) Visit ​http://localhost:8000/demo/1 -- Notice all items in contents are unselected. This is NOT expected.

The difference between (5) and (6) is the form_class used in the view for (6) uses a to_field_name parameter which is not id.

Python: 3.4,
Linux Mint 17,
Django 1.9.4

[Tim Graham]

Duplicate of #17657.