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Thomas De Schampheleire

utils: move repo_name_slug to utils2 to prevent import cycle on setup_db

After commit 57a733313e4f, 'gearbox setup-db -c my.ini' fails with an import
cycle as follows:

Traceback (most recent call last):
File "/home/tdescham/repo/contrib/kallithea/venv/kallithea-release/bin/gearbox", line 11, in <module>
sys.exit(main())
File "/home/tdescham/repo/contrib/kallithea/venv/kallithea-release/lib/python2.7/site-packages/gearbox/main.py", line 199, in main
return gearbox.run(args)
File "/home/tdescham/repo/contrib/kallithea/venv/kallithea-release/lib/python2.7/site-packages/gearbox/main.py", line 145, in run
return self._run_subcommand(remainder)
File "/home/tdescham/repo/contrib/kallithea/venv/kallithea-release/lib/python2.7/site-packages/gearbox/main.py", line 149, in _run_subcommand
subcommand = self.command_manager.find_command(argv)
File "/home/tdescham/repo/contrib/kallithea/venv/kallithea-release/lib/python2.7/site-packages/gearbox/commandmanager.py", line 78, in find_command
cmd_factory = cmd_ep.resolve()
File "/home/tdescham/repo/contrib/kallithea/venv/kallithea-release/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2324, in resolve
module = __import__(self.module_name, fromlist=['__name__'], level=0)
File "/home/tdescham/repo/contrib/kallithea/kallithea-release/kallithea/lib/paster_commands/setup_db.py", line 27, in <module>
from kallithea.lib.db_manage import DbManage
File "/home/tdescham/repo/contrib/kallithea/kallithea-release/kallithea/lib/db_manage.py", line 47, in <module>
from kallithea.model.repo_group import RepoGroupModel
File "/home/tdescham/repo/contrib/kallithea/kallithea-release/kallithea/model/repo_group.py", line 35, in <module>
import kallithea.lib.utils
File "/home/tdescham/repo/contrib/kallithea/kallithea-release/kallithea/lib/utils.py", line 48, in <module>
from kallithea.model.repo_group import RepoGroupModel
ImportError: cannot import name RepoGroupModel

i.e. kallithea.model.repo_group wants to import kallithea.lib.utils which
in turn wants to import kallithea.model.repo_group.

In fact there exists kallithea.lib.utils and kallithea.lib.utils2.
The current split is that 'utils2' contains 'simple' utilities, none of which
depend on kallithea models, controllers, ... In contrast, 'utils' does rely
on such kallithea classes.

As kallithea.model.repo_group was only include kallithea.lib.utils for its
repo_name_slug method, which has no dependency on other kallithea classes,
move that method (and its dependent recursive_replace) to
kallithea.lib.utils2 instead. This fixes the import cycle.

=======================
Database schema changes
=======================

Kallithea uses Alembic for :ref:`database migrations <upgrade_db>`
(upgrades and downgrades).

If you are developing a Kallithea feature that requires database schema
changes, you should make a matching Alembic database migration script:

1. :ref:`Create a Kallithea configuration and database <setup>` for testing
   the migration script, or use existing ``development.ini`` setup.

   Ensure that this database is up to date with the latest database
   schema *before* the changes you're currently developing. (Do not
   create the database while your new schema changes are applied.)

2. Create a separate throwaway configuration for iterating on the actual
   database changes::

    gearbox make-config temp.ini

   Edit the file to change database settings. SQLite is typically fine,
   but make sure to change the path to e.g. ``temp.db``, to avoid
   clobbering any existing database file.

3. Make your code changes (including database schema changes in ``db.py``).

4. After every database schema change, recreate the throwaway database
   to test the changes::

    rm temp.db
    gearbox setup-db -c temp.ini --repos=/var/repos --user=doe --email doe@example.com --password=123456 --no-public-access --force-yes
    gearbox repo-scan -c temp.ini

5. Once satisfied with the schema changes, auto-generate a draft Alembic
   script using the development database that has *not* been upgraded.
   (The generated script will upgrade the database to match the code.)

   ::

    alembic -c development.ini revision -m "area: add cool feature" --autogenerate

6. Edit the script to clean it up and fix any problems.

   Note that for changes that simply add columns, it may be appropriate
   to not remove them in the downgrade script (and instead do nothing),
   to avoid the loss of data. Unknown columns will simply be ignored by
   Kallithea versions predating your changes.

7. Run ``alembic -c development.ini upgrade head`` to apply changes to
   the (non-throwaway) database, and test the upgrade script. Also test
   downgrades.

   The included ``development.ini`` has full SQL logging enabled. If
   you're using another configuration file, you may want to enable it
   by setting ``level = DEBUG`` in section ``[handler_console_sql]``.

The Alembic migration script should be committed in the same revision as
the database schema (``db.py``) changes.

See the `Alembic documentation`__ for more information, in particular
the tutorial and the section about auto-generating migration scripts.

.. __: http://alembic.zzzcomputing.com/en/latest/


Troubleshooting
---------------

* If ``alembic --autogenerate`` responds "Target database is not up to
  date", you need to either first use Alembic to upgrade the database
  to the most recent version (before your changes), or recreate the
  database from scratch (without your schema changes applied).