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(for upgrading users, please see the notes at the bottom) Bazel brought a lot of nice things to the table, such as rebuilds based on content changes instead of modification times, caching of build products, detection of incorrect build rules via a sandbox, and so on. Rewriting the build in Bazel was also an opportunity to improve on the Makefile-based build we had prior, which was pretty poor: most dependencies were external or not pinned, and the build graph was poorly defined and mostly serialized. It was not uncommon for fresh checkouts to fail due to floating dependencies, or for things to break when trying to switch to an older commit. For day-to-day development, I think Bazel served us reasonably well - we could generally switch between branches while being confident that builds would be correct and reasonably fast, and not require full rebuilds (except on Windows, where the lack of a sandbox and the TS rules would cause build breakages when TS files were renamed/removed). Bazel achieves that reliability by defining rules for each programming language that define how source files should be turned into outputs. For the rules to work with Bazel's sandboxing approach, they often have to reimplement or partially bypass the standard tools that each programming language provides. The Rust rules call Rust's compiler directly for example, instead of using Cargo, and the Python rules extract each PyPi package into a separate folder that gets added to sys.path. These separate language rules allow proper declaration of inputs and outputs, and offer some advantages such as caching of build products and fine-grained dependency installation. But they also bring some downsides: - The rules don't always support use-cases/platforms that the standard language tools do, meaning they need to be patched to be used. I've had to contribute a number of patches to the Rust, Python and JS rules to unblock various issues. - The dependencies we use with each language sometimes make assumptions that do not hold in Bazel, meaning they either need to be pinned or patched, or the language rules need to be adjusted to accommodate them. I was hopeful that after the initial setup work, things would be relatively smooth-sailing. Unfortunately, that has not proved to be the case. Things frequently broke when dependencies or the language rules were updated, and I began to get frustrated at the amount of Anki development time I was instead spending on build system upkeep. It's now about 2 years since switching to Bazel, and I think it's time to cut losses, and switch to something else that's a better fit. The new build system is based on a small build tool called Ninja, and some custom Rust code in build/. This means that to build Anki, Bazel is no longer required, but Ninja and Rust need to be installed on your system. Python and Node toolchains are automatically downloaded like in Bazel. This new build system should result in faster builds in some cases: - Because we're using cargo to build now, Rust builds are able to take advantage of pipelining and incremental debug builds, which we didn't have with Bazel. It's also easier to override the default linker on Linux/macOS, which can further improve speeds. - External Rust crates are now built with opt=1, which improves performance of debug builds. - Esbuild is now used to transpile TypeScript, instead of invoking the TypeScript compiler. This results in faster builds, by deferring typechecking to test/check time, and by allowing more work to happen in parallel. As an example of the differences, when testing with the mold linker on Linux, adding a new message to tags.proto (which triggers a recompile of the bulk of the Rust and TypeScript code) results in a compile that goes from about 22s on Bazel to about 7s in the new system. With the standard linker, it's about 9s. Some other changes of note: - Our Rust workspace now uses cargo-hakari to ensure all packages agree on available features, preventing unnecessary rebuilds. - pylib/anki is now a PEP420 implicit namespace, avoiding the need to merge source files and generated files into a single folder for running. By telling VSCode about the extra search path, code completion now works with generated files without needing to symlink them into the source folder. - qt/aqt can't use PEP420 as it's difficult to get rid of aqt/__init__.py. Instead, the generated files are now placed in a separate _aqt package that's added to the path. - ts/lib is now exposed as @tslib, so the source code and generated code can be provided under the same namespace without a merging step. - MyPy and PyLint are now invoked once for the entire codebase. - dprint will be used to format TypeScript/json files in the future instead of the slower prettier (currently turned off to avoid causing conflicts). It can automatically defer to prettier when formatting Svelte files. - svelte-check is now used for typechecking our Svelte code, which revealed a few typing issues that went undetected with the old system. - The Jest unit tests now work on Windows as well. If you're upgrading from Bazel, updated usage instructions are in docs/development.md and docs/build.md. A summary of the changes: - please remove node_modules and .bazel - install rustup (https://rustup.rs/) - install rsync if not already installed (on windows, use pacman - see docs/windows.md) - install Ninja (unzip from https://github.com/ninja-build/ninja/releases/tag/v1.11.1 and place on your path, or from your distro/homebrew if it's 1.10+) - update .vscode/settings.json from .vscode.dist
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Contributing Code
For info on contributing things other than code, such as translations, decks and add-ons, please see https://docs.ankiweb.net/contrib
With most users now on 2.1, the past 2 years have been focused on paying down some of the technical debt that Anki's codebase has built up over the years, and making changes that will make future maintenance and refactoring easier. A lot of Anki's "business logic" has been migrated to Rust, which AnkiMobile and AnkiDroid can also take advantage of - previously a lot of effort was wasted writing the same code for each platform, and then debugging differences in the implementations. Considerable effort has also been put into improving the Python side of things, with type hints added to the majority of the codebase, automatic linting/formatting, and refactoring of parts of the code.
The import/export code remains to be done, and this will likely take a number of months to work through. Until that is complete, new features will not be the top priority, unless they are easy wins as part of the refactoring process.
If you are planning to contribute any non-trivial changes, please reach out on the support site before you begin work. Some areas (primarily pylib/) are likely to change/conflict with other work, and larger changes will likely need to wait until the refactoring process is done.
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.
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.
Translations
For information on adding new translatable strings to Anki, please see https://translating.ankiweb.net/anki/developers
Tests Must Pass
Please make sure 'ninja 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
./ninja check
You may want to explicitly set PATH to your normal shell PATH in that script, as pre-commit does not use a login shell, and if your path differs Bazel will end up recompiling things unnecessarily.
If your change is non-trivial and not covered by the existing unit tests, please consider adding a unit test at the same time.
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.
License
Please add yourself to the CONTRIBUTORS file in your first pull request.