anki/docs/contributing.md

Contributing Code

For info on contributing things other than code, such as translations, decks and add-ons, please see the contribution guide.

Help wanted

If you'd like to contribute but don't know what to work on, please take a look at the issues tab of the Anki repo on GitHub.

Larger changes

Before starting work on larger changes, especially ones that aren't listed on the issue tracker, please reach out on the forums before you begin work, so we can let you know whether they're likely to be accepted or not. When you spent a bunch of time on a PR that ends up getting rejected, it's no fun for either you or us.

Consider an Add-on First

Before submitting a PR for a new feature, please consider whether it could be implemented as an add-on instead. We aim to keep the core Anki codebase lean and maintainable. Many great ideas are better served as add-ons, where they can iterate faster and serve specific user needs without affecting all users.

See the Add-on API documentation for guidance on building add-ons.

Pull Request Description

When opening a pull request, fill in the provided template (.github/pull_request_template.md). It covers the required fields: linked issue, summary/motivation, how to test, and UI evidence for visual changes.

Linked Issues

Every pull request, except hotfixes and dependency updates, must be linked to an existing open issue. If no issue exists, please open one to describe the problem before submitting a PR. This helps us ensure we're solving the right problems and prevents wasted effort on both sides.

PRs without a linked issue may be automatically closed after a short period.

Dependency updates

Dependabot PRs do not need a linked issue. Maintainers should follow Dependabot updates when reviewing or landing them.

Refactoring

Please avoid PRs that focus on refactoring. Every PR has a cost to review, and a chance of introducing accidental regressions, and often these costs are not worth it for slightly more elegant code.

That's not to say there's no value in refactoring. But such changes are usually better done in a PR that happens to be working in the same area - for example, making small changes to the code as part of fixing a bug, or a larger refactor when introducing a new feature.

Type hints

Most of Anki's Python code now has type hints, which improve code completion, and make it easier to discover errors during development. When adding new code, please make sure you add type hints as well, or the tests will fail.

Qt's stubs are not perfect, so you may sometimes need to use cast(), or silence a type error. When connecting signals, there's a qconnect() helper in aqt.utils that can be used to work around the type warnings without obscuring other errors such as a mistyped variable.

In cases where you have two modules that reference each other, you can fix the import cycle by using fully qualified names in the types, and enabling annotations. For example, instead of

from aqt.browser import Browser

def myfunc(b: Browser) -> None:
  pass

use the following instead:

from __future__ import annotations

import aqt

def myfunc(b: aqt.browser.Browser) -> None:
  pass

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 tense "changed" can seem awkward, but makes it consistent with "will", and is similar to the naming style used in iOS's libraries.

In most cases, hooks are better added in the GUI code than in pylib.

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 will update the generated files.

If you want to change an existing hook to, for example, receive an additional argument, you must leave the existing hook unchanged to preserve backwards compatibility. Create a new definition for your hook with a similar name and include the properties replaces="name_of_old_hook" and replaced_hook_args=["..."] in the definition of the new hook. If the old hook has a legacy hook, you must not add the legacy hook to the definition of the new hook.

Translations

For information on adding new translatable strings to Anki, please see the translation guide.

For information on translating the documentation, please see translating the manual.

Tests Must Pass

Please make sure 'ninja check' completes successfully before submitting code.

pre-commit is used to run that check from a Git hook. It is configured in .pre-commit-config.yaml at the repository root. After installing the dev dependencies (for example uv sync --group dev), run one of:

uv run pre-commit install --hook-type pre-push

python3 -m pre_commit install --hook-type pre-push

(pre-commit alone only works if that executable is on your PATH, for example after pip install --user pre-commit or with your virtual environment activated.)

The bundled hook runs ./ninja check on pre-push (not on every commit), because the full check suite can take a long time. You can still run ./ninja check manually at any time.

You may need to ensure your usual shell PATH is visible to the hook (for example if tools such as ninja are installed outside standard locations), because pre-commit does not use a login shell and a different path can cause extra rebuilds.

New or changed behavior must be covered by tests. Exceptions where tests are not required: version bumps, documentation-only changes, translation updates, dependency updates, and CI/build housekeeping (chore).

Code Style

Please use standard Python snake_case variable names and functions in newly introduced code. Because add-ons often rely on existing function names, if renaming an existing function, please add a legacy alias to the old function.

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.

AI-Assisted Contributions

Using AI tools to help write or review code is permitted. However, you must understand every change you submit. If you cannot explain what your changes do and how they interact with the rest of the system, your PR will be closed.

Please review AI-generated code carefully before submitting. PRs that appear to have been submitted without human review — e.g., irrelevant code, duplicate logic, or comments that don't match the implementation — may be closed without further discussion.

License

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