anki/README.contributing

Contributing Code
==================

For info on contributing things other than code, such as translations, decks
and add-ons, please see http://ankisrs.net/docs/manual.html#contributing

With most users now on 2.1, it's time to start paying down some of the
technical debt that Anki's codebase has built up over the years. This is
not an easy task - the code is tightly coupled together, not fully covered
by unit tests, and mostly dynamically typed, meaning even small changes
carry the risk of regressions.

So to start with, the primary focus is on changes that will make future
maintenance and refactoring easier - improving tooling and linting, static
type checking, more unit tests, and so on. Contributions that move the code in
this direction or fix bugs would be appreciated.

If you would like to add a new feature or alter existing functionality in the
Python code, please reach out on the support site before you begin work, as
some changes may be more appropriately done in an add-on instead.

Please hold off on large refactoring projects for now, as it risks introducing
bugs, and many addons currently rely on certain variable/method names and
type signatures. If you're working on an isolated part of the codebase
covered by unit tests, then such changes may be accepted, but larger changes
are less likely to be at this time.

Type hints
-----------

Type hints have recently been added to parts of the codebase, mainly using
automated tools. At the moment, large parts of the codebase are still missing
type hints, and some of the hints that do exist are incorrect or too general.

When running 'make check', Anki uses mypy to typecheck the code. Mypy only
checks functions that have type signatures, so adding more type signatures to
the code increases the amount of code that mypy is able to analyze.

Patches that improve the type hints would be appreciated. And if you're
adding new functionality, please use type hints in the new code you write
where practical.

Parts of Anki's codebase use ad-hoc data structures like nested dictionaries
and lists, and they can be difficult to fully type. Don't worry too much about
getting the types perfect - even a partial type like Dict[str, Any] or
List[Tuple] is an improvement over no types at all.

Anki bundles Qt stubs, but they are not perfect, so you'll find when doing
things like connecting signals, you may have to add the following to the end
of a line to silence the spurious errors.

 # type: ignore

In cases where you have two modules that reference each other, you can't simply
import the types from each module into the other one, as it can cause a cyclic
import. An example of how to work around this can be seen at
https://github.com/dae/anki/commit/ed0b3d337458d7161811547932b6476f2d4bc887

Hooks
-------

If you're writing an add-on and would like to extend a function that doesn't
currently have a hook, a pull request that adds the required hooks would be
welcome. If you could mention your use case in the pull request, that would be
appreciated.

The hooks try to follow one of two formats:

[subject] [verb] - eg, note_type_added, card_will_render

[module] [verb] [subject] - eg, browser_did_change_row, editor_did_update_tags

The qt code tends to use the second form as the hooks tend to focus on
particular screens. The pylib code tends to use the first form, as the focus
is usually subjects like cards, notes, etc.

Using "did change" instead of the past test "changed" can seem awkward, but
makes it consistent with "will", and is similar to the naming style used in
iOS's libraries.

The hook code is automatically generated using the definitions in
pylib/tools/genhooks.py and qt/tools/genhooks_gui.py. Adding a new definition
in one of those files and running 'make develop' will update pylib/anki/hooks
.py or qt/aqt/gui_hooks.py.

Tests Must Pass
----------------

Please make sure 'make check' completes successfully before submitting code.
You can do this automatically by adding the following into
.git/hooks/pre-commit or .git/hooks/pre-push and making it executable.

#!/bin/bash
set -e
make check

You may need to adjust the PATH variable so that things like a local install
of cargo can be found.

If your change is to anki/ and not covered by the existing unit tests, please
consider adding a unit test at the same time.

Code Style
------------------

You are welcome to use snake_case variable names and functions in newly
introduced code, but please avoid renaming existing functions and global
variables that use camelCaps. Variables local to a function are safer to
rename, but please do so only when a function needs to be changed for other
reasons as well.

Code formatting is automatically done when you use "make fix".

Do One Thing
-------------

A patch or pull request should be the minimum necessary to address one issue.
Please don't make a pull request for a bunch of unrelated changes, as they are
difficult to review and will be rejected - split them up into separate
requests instead.

License
-------

Please add yourself to the CONTRIBUTORS file in your first pull request.