Re: [mezzanine-users] Re: Extra model fields at Mezzanine's derived package ?

[joanbm]

Thanks Ryne, for the explanation of MIGRATION_MODULES setting.

I've finally dealt with extension migrations and avoided burden of other 
apps migrations shipping at the same time.

For a reference, brief info which seems to work with Django 1.8+


   1. assign extra model fields in package's *__init__* like mezzanine does 
   # deferred fields assignment
   django.db.models.signals.class_prepared(add_extra_model_fields, weak=
   False)
   
   def add_extra_model_fields(sender,**kwargs):
  ...
  field = django.db.models.(...)
  field.contribute_to_class(,'')
   
   2. hand-written migration of extension's package 
   from __future__ import unicode_literals
   from django.db import migrations, models
   
   # Trick django migration runs for other application
   TARGET_APP = 'shop'
   
   
   class Migration(migrations.Migration):
   # Change to intended application label
   def __init__(self, name, app_label):
   super(Migration, self).__init__(name, TARGET_APP)
   
   dependencies = [
   ('shop', '0007_auto_20150921_2323'),
   ('cartridgex', '0002_productproperties_variation'),
   ]
   
   # Django would consider this migration as 'squashed'
   replaces = (
   ('shop', '0008_productvariation_tax'),
   )
   
   operations = [
  migrations.AddField(
 ...
   
   

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Re: [mezzanine-users] Re: Extra model fields at Mezzanine's derived package ?

[joanbm]

> Without knowing exactly which models you're modifying, I would recommend 
> to avoid field injection in reusable apps. If you're injecting stuff on 
> Page, it might be better to create a custom Page type and distribute 
> that with your package. See: 
>
I extend models which are not designed as swappable as 
cartridge.shop.ProductVariation, ProductOption, CartItem, Orde or 
mezzanine.blog.BlogPost etc.
 

>  
>
If you still want to go with the field injection route, there are a few 
> approaches that I know of: 
>
> - Maintain your own migration history for modified models using Django's 
> MIGRATION_MODULES 
>
> http://mezzanine.readthedocs.io/en/latest/model-customization.html#field-injection-caveats
>  
>
> I'm aware of this option, but it is a dictionary with application name as 
a key, right ? How can I tell Django to look for *cartridge.shop* 
migrations both at original path and my extension package ?

- Add support for "out of app" migrations to Django 
> http://bitofpixels.com/blog/upgrading-to-mezzanine-4/ 
> 
>  
> (see the 
> EXTRA_MODEL_FIELDS section) 
>
> Tried trick django with "out of app" migrations by altering their app 
label in initializer, but getting cyclic errors for ForeignKey fields.
 

> - Create a model with your extra fields and couple it with a OneToOne 
> field. 
>
 Yes, but it would require big code refactoring, loss of logical 
separateness, less effectiveness as whole model loaded even when some parts 
won't be used ...

Anyway thanks for your reply.

I may come with specific migration error if there even exists some solution 
without monkeypatching Django itself.
 

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[mezzanine-users] Re: Extra model fields at Mezzanine's derived package ?

[joanbm]

 Fixed *class_prepared* signal call (due to weak reference to handler) but 
issue with migrations remains.
 

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[mezzanine-users] Extra model fields at Mezzanine's derived package ?

[joanbm]

Hello,

I've built Mezzanine/Cartridge based project with lot of generic code 
suited for other similar projects.
I'd like to separate it in a standalone package - extension and use it as 
other 3rd party Django apps.

There is however a problem. It extends Mezzanine and Cartridge models with 
additional fields by `EXTRA_MODEL_FIELDS` mechanism, but it works AFAIK for 
target project only, in its settings.
I'm looking for some advice how build such extension, without retire to 
subclassing, thus introducing original n+1 query problem.

Played with manual call to `contribute_to_class` new field's method through 
`class_prepared` signal in package's init file, but registered function is 
never called. Also have no idea how write migrations, because Django/South 
couldn't generate them.



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[mezzanine-users] How create AUTH_PROFILE_MODULE to work at checkout ?

[joanbm]

When set *AUTH_PROFILE_MODULE* in *settings.py*, Cartridge should attempt 
retrieve existing profile data and fill matched fields in checkout form.

If not stored in a session or last order, it fetches them from User 
profile. And here are the troubles.

By the cartridge.shop.checkout.initial_order_data 

 function, 
it tries profile model and model from request, in that order, but they are 
in different unrelated types.
*request.user* is of *SimpleLazyObject* and *get_profile_for_user* returns 
normal instance of *django.db.models.Model* descendant. But it latter case 
it never works, because *profile model fields are not callable* and the 
condition won't eval to true.

Any idea what should custom AUTH_PROFILE_MODULE provide to work with 
checkout code ?


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