:date: 2017-12-10

=========================
Sunday, December 10, 2017
=========================

I had a review of the :ref:`lino.dev`, trying to feel like a student
of the `Tallinn IT college <http://www.itcollege.ee/>`.  The first
thing that made me stumble was the fact that I need to work in
Python 2.

Our work on :ticket:`36` is almost done, but it went to sleep because
we depend on appy.

The appypod project, aartial redistribution of appy
===================================================

Don't take it personally Gaetan, but now I will try a partial
redistribute of appy.

The idea is that I redistribute Gaetan's work on `appy.pod` in a
project with a git repository and a :xfile:`setup.py`.

The sole purpose is making Gaetan's work on `appy.pod` available under
Python 3. I don't plan any enhancements.

Note that appy.pod is only a part of the Appy framework. We reduce the
redistribution to a minimum because we don't want to be a replacement.



Porting Lino to Django 2
========================

The first stumblestone for Lino under Django 2 is that they somehow
decided to make `on_delete` a required argument::

  TypeError: __init__() missing 1 required positional argument: 'on_delete'

I fix this by changing all :class:`models.ForeignKey` calls to
:func:`lino.core.fields.ForeignKey`.

Next problem::

  AttributeError: 'Options' object has no attribute 'virtual_fields'

That's because virtual_fields has been replaced by private_fields
in 1.9. Already in 1.10 we had:

- The private attribute virtual_fields of Model._meta is deprecated in
  favor of private_fields.

- The private keyword arguments virtual_only in
  Field.contribute_to_class() and virtual in Model._meta.add_field()
  are deprecated in favor of private_only and private, respectively.

Next problem::

  Exception: Invalid remote field account__ref for <class 'lino_xl.lib.finan.models.JournalEntryItem'>

That's because Field.rel and Field.remote_field.to are removed.
Already in `1.9
<https://docs.djangoproject.com/en/5.0/releases/1.9/#field-rel-changes>`__,
"Field.rel and its methods and attributes have changed to match the
related fields API. The Field.rel attribute is renamed to remote_field
and many of its methods and attributes are either changed or renamed."

Until no I could test::

    if fk.remote_field is not None: ...

But in Django 2, fk.remote_field is False when it was None.

django-admin commands now have more severe argument checking.

Voilà. A nice start. It's not finished, the next problem is somewhere
in mti, that's enough Django 2 for me for today. I said::

  install_requires.append('django<2')

because after all I first want it to pass under Python 3 at all.