# Code Code changes ============ Tests ----- If at all practicable, all new code should be tested to some extent. If writing a test is hard, we need to prioritize making it easier, and potentially block features if that is the case. Documentation ------------- Reference documentation should be added, in addition to release notes (`doc/manual/rl-next-dev`), for user visible changes. For notable dev facing changes, consider adding release notes in `doc/manual/rl-next-dev`. This is not critical for all changes; in some cases it may make more sense to write it up in dev documentation instead, and indeed it may be ok to defer writing that dev documentation (it's helpful to create an issue to not forget). Benchmarking ------------ Changes that touch the core of the evaluator or other performance critical code in Lix should be benchmarked. See [bench/README.md](https://git.lix.systems/lix-project/lix/src/branch/main/bench) for instructions. Changelist size --------------- If a CL is too long to review, it should be split up into smaller pieces with tests. The exact length varies but passing the 1000 line mark should give significant thought to splitting. - When a CL is split, each commit should still be a valid state (tests passing, etc). If you must, you can gate in-progress changes with a flag or similar until the final commit. (Qyriad) Commit messages --------------- Include at least a sentence or two as to why you are making a commit. For example, it can be nice to have the reproduction of a bug in the commit message. The commit message *is* the message for your review. There's no particular format or specific style for commit messages; just make sure they're descriptive and informative. C++ === While we hope to migrate the Lix interpreter from C++ to Rust eventually, C++ is a language that is likely to exist for a long time, and we may end up having to use it in other contexts. Lix is a C\+\+20 codebase. Features of C\+\+20 that compile on all supported platforms can be used. NULL vs nullptr --------------- `nullptr` where at all possible. Static vs anonymous namespace ----------------------------- Prefer anonymous namespace, both currently exist in the codebase (jade: any other opinions?). Type Aliases with `typedef` vs `using` ---------------------------------- Prefer `using` declarations, as they can be used in more places, can be templatized, and have clearer syntax. Both currently exist in the codebase. (Qyriad) TODO/FIXME/XXX Comments ----------------------- jade: this is not consistent with the conventions I use, needs further discussion imo (TODO: block in pre-commit hook, used in local tree but should never pass code review, FIXME(name||feature): its busted, someone should go fix it later, XXX: this is bad, we are writing down that it is ugly but leaving it as-is as we didn't figure out a better way) Something along the lines of: - **TODO**: acknowledgement that something is acceptably-for-now incomplete, especially if the scope of fixing it is high or unknown - **FIXME**: this should be fixed before the feature or major change that it's a part of is considered "ready" - **XXX**: this should not pass code review and should be considered a left-in mistake Header files ------------ ### Filenames Headers should end with `.hh`. This reduces the likelihood anyone will try to include them from C files, which would require following the rules of both languages and is easy to get wrong. The implementation of the functions declared in a `.hh` file should be in a `.cc` file of the same name, absent reasons to do otherwise. ### Order-independence Headers should not care what order they're loaded in. The exception, for now, is `config.h` in the `lix` repo. This must always come before all other headers. This observation should not be taken to imply it must always be that way, but at the moment it's helpful to be aware of. ### Idempotence Use `#pragma once`, it helps. You can see this in most existing header files. ### `///@file` and header documentation `///@file` should be at the top of all nix headers - Doxygen and other tools use it to decide whether a header should have documentation generated for definitions in it. See [the relevant Doxygen documentation](https://www.doxygen.nl/manual/docblocks.html#structuralcommands) for more details. Strongly consider adding a description of the purpose of a header file at the top of it in with `@brief A sentence saying what it is for`. Examples: ``` /** * @file * @brief This header is for meow meow cat noises. */ ``` ``` /// @file /// @brief meow meow meow ``` Source files ------------ ### Filenames Source files should end with `.cc`. Python ====== Python is a widely used tooling language in the Lix codebase. It's used in the test suite in `functional2`, a pytest based test suite intending to replace the Bash `functional` test suite. It's what the release engineering in `releng/` is written in. In general, follow PEP-8 while writing Python code: identifier style should be the typical Python one per PEP-8, indents are 4 spaces, etc. In the near future, we will autoformat Python code with `ruff`. ## Type annotations Type annotations should be used where they are helpful, and should be used for parameter and return types of functions. If it is too much of a bother to convince the type checker of something, it is acceptable to put an Any there. Prefer inserting Any if the alternative is lying to the type checker via `# type: ignore` comments. `dataclasses` is a useful library that produces nicer, more typed, code, and it is widely used. It's the correct choice for most classes which are just blobs of data. ## Doc strings Please write them. Single-line ones are better than none at all. We use the Sphinx docstring format for parameter documentation, though we currently do not generate Sphinx docs for our Python codebases. See [this Sphinx tutorial][sphinx-tutorial] for an example and the [Sphinx domains reference] for reference. [Sphinx domains reference]: https://www.sphinx-doc.org/en/master/usage/domains/index.html [sphinx-tutorial]: https://sphinx-rtd-tutorial.readthedocs.io/en/latest/docstrings.html Nix language ============ Unsurprisingly Nix contains Nix code. Some amount is tests and a lot is packaging. We use the nixfmt formatter on files outside the test suite. It's run through `treefmt` with `pre-commit` hooks. Nix code outside the test suite is expected to be formatted. Test suite files need not be formatted with the formatter at this time, but please consider doing so with new tests that don't rely on formatting. with ---- Prefer not to use `with` to bring things into scope as it obscures the source of variables and degrades language server diagnostics. Use `let inherit (attrset) attrs` instead. Meson ===== Generally based on the style in Meson's docs made consistent and with a couple tweaks; notably multiline function calls are done in "block style" (think like rustfmt does it), rather than aligned, e.g.: ```meson executable('sdlprog', 'sdlprog.c', win_subsystem : 'windows', dependencies : sdl2_dep, ) ``` rather than: ```meson executable('sdlprog', 'sdlprog.c', win_subsystem : 'windows', dependencies : sdl2_dep) ``` Meson's docs go back and forth on this, but we also put a space before and after the colon for keyword arguments (so `win_subsystem : 'windows'`, rather than `win_subsystem: 'windows'`).