Django 1.8 support

[chhantyal]

I am alpha testing Django 1.8

Meta API is formalised in 1.8 and as a result, method get_fields_with_model is deprecated.

That method is used here

django-mptt/mptt/managers.py

Line 76 in 6a41fd4

for fld in model._meta.get_fields_with_model()

Because of this, project which is on 1.7 is not able to to run on 1.8. Please refer to migration docs https://docs.djangoproject.com/en/1.8/ref/models/meta/#migrating-old-meta-api

[craigds]

I don't see this result when running the tests (tox -e py27-master). Could you supply a test model that shows the problem?

[chhantyal]

Hey thanks for quick response.

I created a test app here https://github.com/chhantyal/mptt-test

With model https://github.com/chhantyal/mptt-test/blob/master/mptt_test/app/models.py

Just clone, install requirements and run 'makemigrations' or any other commands. It will give error.

Here is traceback http://dpaste.com/246NP6F

This is issue with PyPi version as well as master branch

[craigds]

Interesting. Seems this happens because django 1.8 no longer lets you call ._meta.get_fields before the models have been fully loaded.

It's possible this code is all obsolete - from my brief reading of the ModelBase code it looks like all fields should be added to the model class before TreeManager.init_from_model() is called, so we shouldn't need to call get_fields() at all. Hopefully I'll have time in the next few days to investigate this.

If that doesn't pan out, we could probably work around this by doing TreeManager.init_from_model() in a AppConfig.ready() hook, but that might have it's own problems (and it necessitates two very separate code paths for django 1.6 and 1.7+)

[carltongibson]

I bumped into this playing with 1.8a1.

A quick work-around:

1. Change model superclass to django.models.Model.
2. Implement AppConfig.ready and call mptt.register there.

This seems to work OK, for the now.

[chhantyal]

@carlospalol wow, that looks very clever. Thanks. At least I can work with 1.8 until official support comes.

[claudep]

See also https://code.djangoproject.com/ticket/24231

[mazing]

Does anyone have a work-around?

[craigds]

Current status: waiting to see what the outcome of that Django ticket is before implementing a fix.

[craigds]

The upstream ticket has been closed (wontfix). Seems a possible solution is to call TreeManager.init_from_model() from the AppCache.ready signal on django 1.8.

[craigds]

a note re this fix: AppConfig.ready() is actually not a suitable place for this, because we need to do this init before that's called so we can determine what model to add the tree fields on.

But it turns out we don't need to inspect the fields at all to do what we need - just need to find the topmost concrete model base in the mro() which is a MPTTModel subclass. This simplifies things quite a bit so I went with that.

Thanks for the bug reports. I don't intend to backport django 1.8 support to 0.6.x, but a 0.7 release probably isn't too far off.

[chhantyal]

Thank you. That's great - we will be fine using master branch for now as Django 1.8 is not yet released 👍

[claudep]

As Django 1.8 is around the corner, it would be great if an 1.8-compatible release could be published on PyPI.

[chhantyal]

Hi @craigds
Now 1.8 is released, I think it's time to update PyPi?

[ttanner]

HEAD works fine for me with Django 1.8. please release it

[hassek]

Yep, waiting for this too :)

[craigds]

Done :)

[claudep]

Thanks Craig, awesome!