neovim/CONTRIBUTING.md
2021-10-05 08:01:09 -07:00

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Contributing to Neovim
======================
Getting started
---------------
If you want to help but don't know where to start, here are some
low-risk/isolated tasks:
- [Merge a Vim patch].
- Try a [good first issue](../../labels/good-first-issue) or [complexity:low] issue.
- Fix bugs found by [Clang](#clang-scan-build), [PVS](#pvs-studio) or
[Coverity](#coverity).
- [Improve documentation][wiki-contribute-help]
Reporting problems
------------------
- [Check the FAQ][wiki-faq].
- [Search existing issues][github-issues] (including closed!)
- Update Neovim to the latest version to see if your problem persists.
- Try to reproduce with `nvim --clean` ("factory defaults").
- [Bisect](https://neovim.io/doc/user/starting.html#bisect) your config: disable plugins incrementally, to narrow down the cause of the issue.
- [Bisect][git-bisect] Neovim's source code to find the cause of a regression, if you can. This is _extremely_ helpful.
- When reporting a crash, [include a stacktrace](https://github.com/neovim/neovim/wiki/FAQ#backtrace-linux).
- Use [ASAN/UBSAN](#clang-sanitizers-asan-and-ubsan) to get detailed errors for segfaults and undefined behavior.
- Check the logs. `:edit $NVIM_LOG_FILE`
- Include `cmake --system-information` for build-related issues.
Developer guidelines
--------------------
- Read `:help dev` if you are working on Nvim core.
- Read `:help dev-ui` if you are developing a UI.
- Read `:help dev-api-client` if you are developing an API client.
- Install `ninja` for faster builds of Nvim.
```
sudo apt-get install ninja-build
make distclean
make # Nvim build system uses ninja automatically, if available.
```
Pull requests (PRs)
---------------------
- To avoid duplicate work, create a draft pull request.
- Your PR must include [test coverage][run-tests].
- Avoid cosmetic changes to unrelated files in the same commit.
- Use a [feature branch][git-feature-branch] instead of the master branch.
- Use a **rebase workflow** for small PRs.
- After addressing review comments, it's fine to rebase and force-push.
- Use a **merge workflow** for big, high-risk PRs.
- Merge `master` into your PR when there are conflicts or when master
introduces breaking changes.
- Use the `ri` git alias:
```
[alias]
ri = "!sh -c 't=\"${1:-master}\"; s=\"${2:-HEAD}\"; mb=\"$(git merge-base \"$t\" \"$s\")\"; if test \"x$mb\" = x ; then o=\"$t\"; else lm=\"$(git log -n1 --merges \"$t..$s\" --pretty=%H)\"; if test \"x$lm\" = x ; then o=\"$mb\"; else o=\"$lm\"; fi; fi; test $# -gt 0 && shift; test $# -gt 0 && shift; git rebase --interactive \"$o\" \"$@\"'"
```
This avoids unnecessary rebases yet still allows you to combine related
commits, separate monolithic commits, etc.
- Do not edit commits that come before the merge commit.
- During a squash/fixup, use `exec make -C build unittest` between each
pick/edit/reword.
### Stages: Draft and Ready for review
Pull requests have two stages: Draft and Ready for review.
1. [Create a Draft PR][pr-draft] while you are _not_ requesting feedback as
you are still working on the PR.
- You can skip this if your PR is ready for review.
2. [Change your PR to ready][pr-ready] when the PR is ready for review.
- You can convert back to Draft at any time.
Do __not__ add labels like `[RFC]` or `[WIP]` in the title to indicate the
state of your PR: this just adds noise. Non-Draft PRs are assumed to be open
for comments; if you want feedback from specific people, `@`-mention them in
a comment.
### Commit messages
Follow the [conventional commits guidelines][conventional_commits] to *make reviews easier* and to make
the VCS/git logs more valuable. The general structure of a commit message is:
```
<type>([optional scope]): <description>
[optional body]
[optional footer(s)]
```
- Prefix the commit subject with one of these [_types_](https://github.com/commitizen/conventional-commit-types/blob/master/index.json):
- `build`, `ci`, `docs`, `feat`, `fix`, `perf`, `refactor`, `revert`, `test`, `vim-patch`, `chore`
- You can **ignore this for "fixup" commits** or any commits you expect to be squashed.
- Append optional scope to _type_ such as `(lsp)`, `(treesitter)`, `(float)`, …
- _Description_ shouldn't start with a capital letter or end in a period.
- Use the _imperative voice_: "Fix bug" rather than "Fixed bug" or "Fixes bug."
- Try to keep the first line under 72 characters.
- A blank line must follow the subject.
- Breaking API changes must be indicated by
1. "!" after the type/scope, and
2. a "BREAKING CHANGE" footer describing the change.
Example:
```
refactor(provider)!: drop support for Python 2
BREAKING CHANGE: refactor to use Python 3 features since Python 2 is no longer supported.
```
### Automated builds (CI)
Each pull request must pass the automated builds on [sourcehut] and [GitHub Actions].
- CI builds are compiled with [`-Werror`][gcc-warnings], so compiler warnings
will fail the build.
- If any tests fail, the build will fail.
See [test/README.md#running-tests][run-tests] to run tests locally.
Passing locally doesn't guarantee passing the CI build, because of the
different compilers and platforms tested against.
- CI runs [ASan] and other analyzers.
- To run valgrind locally: `VALGRIND=1 make test`
- To run Clang ASan/UBSan locally: `CC=clang make CMAKE_FLAGS="-DCLANG_ASAN_UBSAN=ON"`
- The [lint](#lint) build checks modified lines _and their immediate
neighbors_, to encourage incrementally updating the legacy style to meet our
[style](#style). (See [#3174][3174] for background.)
- CI for freebsd and openbsd runs on [sourcehut].
- To get a backtrace on freebsd (after connecting via ssh):
```sh
sudo pkg install tmux # If you want tmux.
lldb build/bin/nvim -c nvim.core
# To get a full backtrace:
# 1. Rebuild with debug info.
rm -rf nvim.core build
gmake CMAKE_BUILD_TYPE=RelWithDebInfo CMAKE_EXTRA_FLAGS="-DCI_BUILD=ON -DMIN_LOG_LEVEL=3" nvim
# 2. Run the failing test to generate a new core file.
TEST_FILE=test/functional/foo.lua gmake functionaltest
lldb build/bin/nvim -c nvim.core
```
### Clang scan-build
View the [Clang report] to see potential bugs found by the Clang
[scan-build](https://clang-analyzer.llvm.org/scan-build.html) analyzer.
- Search the Neovim commit history to find examples:
```
git log --oneline --no-merges --grep clang
```
- To verify a fix locally, run `scan-build` like this:
```
rm -rf build/
scan-build --use-analyzer=/usr/bin/clang make
```
### PVS-Studio
View the [PVS report](https://neovim.io/doc/reports/pvs/PVS-studio.html.d/) to
see potential bugs found by [PVS Studio](https://www.viva64.com/en/pvs-studio/).
- Use this format for commit messages (where `{id}` is the PVS warning-id)):
```
fix(PVS/V{id}): {description}
```
- Search the Neovim commit history to find examples:
```
git log --oneline --no-merges --grep PVS
```
- Try `./scripts/pvscheck.sh` to run PVS locally.
### Coverity
[Coverity](https://scan.coverity.com/projects/neovim-neovim) runs against the
master build. To view the defects, just request access; you will be approved.
- Use this format for commit messages (where `{id}` is the CID (Coverity ID);
([example](https://github.com/neovim/neovim/pull/804))):
```
fix(coverity/{id}): {description}
```
- Search the Neovim commit history to find examples:
```
git log --oneline --no-merges --grep coverity
```
### Clang sanitizers (ASAN and UBSAN)
ASAN/UBSAN can be used to detect memory errors and other common forms of undefined behavior at runtime in debug builds.
- To build Neovim with sanitizers enabled, use
```
rm -rf build && CMAKE_EXTRA_FLAGS="-DCMAKE_C_COMPILER=clang -DCLANG_ASAN_UBSAN=1" make
```
- When running Neovim, use
```
UBSAN_OPTIONS=print_stacktrace=1 ASAN_OPTIONS=log_path=/tmp/nvim_asan nvim args...
```
- If Neovim exits unexpectedly, check `/tmp/nvim_asan.{PID}` (or your preferred `log_path`) for log files with error messages.
Coding
------
### Lint
You can run the linter locally by:
make lint
The lint step downloads the [master error list] and excludes them, so only lint
errors related to the local changes are reported.
You can lint a single file (but this will _not_ exclude legacy errors):
./src/clint.py src/nvim/ops.c
### Style
- Style rules are (mostly) defined by `src/uncrustify.cfg` which tries to match
the [style-guide]. To use the Nvim `gq` command with `uncrustify`:
```
if !empty(findfile('src/uncrustify.cfg', ';'))
setlocal formatprg=uncrustify\ -q\ -l\ C\ -c\ src/uncrustify.cfg\ --no-backup
endif
```
The required version of `uncrustify` is specified in `uncrustify.cfg`.
- There is also `.clang-format` which has drifted from the [style-guide], but
is available for reference. To use the Nvim `gq` command with `clang-format`:
```
if !empty(findfile('.clang-format', ';'))
setlocal formatprg=clang-format\ -style=file
endif
```
### Navigate
- Set `blame.ignoreRevsFile` to ignore [noise commits](https://github.com/neovim/neovim/commit/2d240024acbd68c2d3f82bc72cb12b1a4928c6bf) in git blame:
```
git config blame.ignoreRevsFile .git-blame-ignore-revs
```
- Use **[universal-ctags](https://github.com/universal-ctags/ctags).**
("Exuberant ctags", the typical `ctags` binary provided by your distro, is
unmaintained and won't recognize many function signatures in Neovim source.)
- Explore the source code [on the web](https://sourcegraph.com/github.com/neovim/neovim).
Reviewing
---------
To help review pull requests, start with [this checklist][review-checklist].
Reviewing can be done on GitHub, but you may find it easier to do locally.
Using [`hub`][hub], you can create a new branch with the contents of a pull
request, e.g. [#1820][1820]:
hub checkout https://github.com/neovim/neovim/pull/1820
Use [`git log -p master..FETCH_HEAD`][git-history-filtering] to list all
commits in the feature branch which aren't in the `master` branch; `-p`
shows each commit's diff. To show the whole surrounding function of a change
as context, use the `-W` argument as well.
[gcc-warnings]: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
[git-bisect]: http://git-scm.com/book/en/v2/Git-Tools-Debugging-with-Git
[git-feature-branch]: https://www.atlassian.com/git/tutorials/comparing-workflows
[git-history-filtering]: https://www.atlassian.com/git/tutorials/git-log/filtering-the-commit-history
[git-history-rewriting]: http://git-scm.com/book/en/v2/Git-Tools-Rewriting-History
[git-rebasing]: http://git-scm.com/book/en/v2/Git-Branching-Rebasing
[github-issues]: https://github.com/neovim/neovim/issues
[1820]: https://github.com/neovim/neovim/pull/1820
[hub]: https://hub.github.com/
[conventional_commits]: https://www.conventionalcommits.org
[style-guide]: https://neovim.io/doc/user/dev_style.html#dev-style
[ASan]: http://clang.llvm.org/docs/AddressSanitizer.html
[run-tests]: https://github.com/neovim/neovim/blob/master/test/README.md#running-tests
[wiki-faq]: https://github.com/neovim/neovim/wiki/FAQ
[review-checklist]: https://github.com/neovim/neovim/wiki/Code-review-checklist
[3174]: https://github.com/neovim/neovim/issues/3174
[sourcehut]: https://builds.sr.ht/~jmk
[GitHub Actions]: https://github.com/neovim/neovim/actions
[Merge a Vim patch]: https://github.com/neovim/neovim/wiki/Merging-patches-from-upstream-Vim
[Clang report]: https://neovim.io/doc/reports/clang/
[complexity:low]: https://github.com/neovim/neovim/issues?q=is%3Aopen+is%3Aissue+label%3Acomplexity%3Alow
[master error list]: https://raw.githubusercontent.com/neovim/doc/gh-pages/reports/clint/errors.json
[wiki-contribute-help]: https://github.com/neovim/neovim/wiki/contribute-%3Ahelp
[pr-draft]: https://docs.github.com/en/github/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request
[pr-ready]: https://docs.github.com/en/github/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/changing-the-stage-of-a-pull-request
[uncrustify]: https://formulae.brew.sh/formula/uncrustify