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Thomas De Schampheleire

templates, controllers: replace webhelpers.html.literal() with webhelpers.html.HTML() where possible

Usage of webhelpers.literal (h.literal) can be a problem when variables are
not correctly escaped. Luckily, this function can be avoided in several
cases.

Several users of the construct:
h.literal(_('..A..') % (..B..))

can be simplified if (..B..) just contains a call to h.link_to. In this
case, there is actually no need to use h.literal, because the object
returned by link_to is already a literal. It is sufficient to use
webhelpers.html.HTML() like so:
h.HTML(_('..A..')) % (..B..)

which is better because it will escape the '..A..' part instead of passing
it literally.

The need to wrap the '..A..' part in HTML() is to make sure the (escaped)
end result is not a plain string but a 'literal' to avoid double escaping
later.

See also the documentation:
https://docs.pylonsproject.org/projects/webhelpers/en/latest/modules/html/builder.html
"
When literal is used in a mixed expression containing both literals and
ordinary strings, it tries hard to escape the strings and return a
literal. However, this depends on which value has “control” of the
expression. literal seems to be able to take control with all
combinations of the + operator, but with % and join it must be on the
left side of the expression. So these all work:

"A" + literal("B")
literal(", ").join(["A", literal("B")])
literal("%s %s") % (16, literal("kg"))

But these return an ordinary string which is prone to double-escaping later:

"\n".join([literal('<span class="foo">Foo!</span>'), literal('Bar!')])
"%s %s" % (literal("16"), literal("<em>kg</em>"))
"

This same escaping with 'HTML()' was already done by default in mako
templates for constructs like ${_("something")} that do not contain format
specifiers. When the translated string _does_ contain format specifiers, we
want to use the same escaping, but we have to do it explicit and earlier so
the escaping happens already when strings are inserted into the template
string.

=======================
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::

    kallithea-cli config-create 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
    kallithea-cli db-create -c temp.ini --repos=/var/repos --user=doe --email doe@example.com --password=123456 --no-public-access --force-yes
    kallithea-cli 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).