# Contributing to Subplot

We would love for you to contribute to the Subplot project, in any way
or form that is good for you. Here are some suggestions to make it as
easy as possible for us to incorporate your contribution. However, you
contributing is more important than you following the guidelines
below.

**Reporting issues, or raising topics for discussion:** Please use the
GitLab issue tracker. If there's an existing issue for what you want
to talk about, please use that, but if not, it's preferable to open a
new issue, as it's easier for the Subplot maintainers to merge issues
than split them. Add tags if you feel they're relevant, but it's OK to
not use tags as well. Issue tags exist primarily to help the
maintainers keep a handle on long lists of issues, and the primary
responsibility is on the maintainers to add the tags that help them.

**Asking for help:** Please use the GitLab issue tracker for this as
well.

**Updating documentation, tests, or code:** Please submit a merge
request via GitLab, or open an issue with a link to a git repository
and branch we can pull from.

**Running the test suite:** For any and all changes that are meant to
change the git repository, the full Subplot test suite must pass. To
run it, use the following command:

```sh
$ ./check -v
```

If you only touch documentation, and don't want to install all the
build dependencies, you can skip running the tests yourself.

**Code formatting:** Rust code must be formatted as if by the
`rustfmt` tool. The test suite checks that.

**Rust version:** We aim for Subplot to be buildable on the stable
version of Debian and the Rust version packaged therein. At this time,
that's Rust version 1.34.

**Python version:** We require Python code to work on Python 3.7 and
later, the version in the current stable version of Debian.

**Portability:** We want Subplot and the test programs it generates to
be portable, but haven't yet defined a list of environments we
explicitly target, apart from the current Debian "stable" on 64-bit Intel
architecture systems ("amd64" in Debian terminology). We try to avoid
breaking compatibility with other environments (other versions of
Debian, other Linux distributions, other Unix variants, other
operating systems) and architecture, but do not currently have the
ability to test that. (Help would be welcome.)

**Keep commits small:** It's easier for us to review smaller commits,
less than about 200 lines of diff, except when each hunk is similar.
For example, if you rename a function, a commit that does that and
nothing else can be quite large, but is easy to review.

**Keep commits integral:** Each commit should be a cohesive change,
not a mix of unrelated changes. If a commit renames a function, it
shouldn't also add a new argument to the function or make other
changes unrelated to the rename.

**Keep commits in a merge request related:** If a commit adds a new
feature, it shouldn't also fix a bug in an old feature. If there's a
need to re-do the new feature, the bug fix will take longer to get
merged.

**Tell a story with a merge request:** The commits in a merge request
should be arranged in a way that make the change as a whole easy to
follow: they "tell a story" of how you would make the set of changes
the second time, knowing everything you know after doing them the
first time.

The goal is not to show the path you originally took, but show how to
get there in the best possible way. You should tell the story of
flying by plane to get somewhere, not how you explored the world and
eventually invented flying machines to travel faster.

# Definition of done

When a change is made to Subplot, it must meet the following minimum
requirements to be considered "done": finished and not requiring
further work or attention.

- if review of the change (in an MR or otherwise) has raised any
  issues, they have been resolved or filed as issues
- the change has been merged to the main branch
- ./check passes after the merge
- all relevant issues have been updated appropriately or closed

# Debugging subplot

Ideally as a **user** of subplot you shouldn't need this, all error messages
should give you sufficient context to chase down your problems. However if you
are debugging a change to subplot itself then you may need to know how
to configure logging.

You can change the logging level of subplot by means of the `SUBPLOT_LOG`
environment variable. If you set it to `trace` then it will show you absolutely
everything traced inside the program. You can learn about the syntax for
this variable on the [env_logger][] docs on `docs.rs`.

[env_logger]: https://docs.rs/env_logger/latest/env_logger/