# Guidelines {#sec-guidelines}

If your contribution tightly follows the guidelines, then there is a good chance
it will be merged without too much trouble. Some of the guidelines will be
strictly enforced, others will remain as gentle nudges towards the correct
direction. As we have no automated system enforcing those guidelines, please
try to double check your changes before making your pull request in order to
avoid "faulty" code slipping by.

If you are uncertain how these rules affect the change you would like to make
then feel free to start a discussion in the [discussions tab](https://github.com/NotAShelf/nvf/discussions)
ideally (but not necessarily) before you start developing.

## Adding Documentation {#sec-guidelines-documentation}

Most, if not all, changes warrant changes to the documentation. Module options
should be documented with [Nixpkgs-flavoured Markdown](https://nixos.org/manual/nixpkgs/unstable/#sec-contributing-markup),
albeit with exceptions.

::: {.note}
As of **v0.5**, **vf** is itself documented using full markdown in both module
options and the manual. With **v0.6**, this manual has also been converted to
markdown in full.
:::

The HTML version of this manual containing both the module option descriptions
and the documentation of **nvf** (such as this page) can be generated and
opened by typing the following in a shell within a clone of the **nvf** Git
repository:

```console
$ nix build .#docs-html
$ xdg-open $PWD/result/share/doc/nvf/index.html
```

## Formatting Code {#sec-guidelines-formatting}

Make sure your code is formatted as described in [code-style
section](#sec-guidelines-code-style). To maintain consistency throughout the
project you are encouraged to browse through existing code and adopt its style
also in new code.

## Formatting Commits {#sec-guidelines-commit-message-style}

Similar to [code style guidelines](#sec-guidelines-code-style) we encourage a
consistent commit message format as described in [commit style
guidelines](#sec-guidelines-commit-style).

## Commit Style {#sec-guidelines-commit-style}

The commits in your pull request should be reasonably self-contained. Which
means each and every commit in a pull request should make sense both on its
own and in general context. That is, a second commit should not resolve an
issue that is introduced in an earlier commit. In particular, you will be
asked to amend any commit that introduces syntax errors or similar problems
even if they are fixed in a later commit.

The commit messages should follow the [seven
rules](https://chris.beams.io/posts/git-commit/#seven-rule), except for
"Capitalize the subject line". We also ask you to include the affected code
component or module in the first line. A commit message ideally, but not
necessarily, follow the given template from home-manager's own documentation

```
  {component}: {description}

  {long description}
```

where `{component}` refers to the code component (or module) your change
affects, `{description}` is a very brief description of your change, and
`{long description}` is an optional clarifying description. As a rare
exception, if there is no clear component, or your change affects many
components, then the `{component}` part is optional. See [example commit
message](#sec-guidelines-ex-commit-message) for a commit message that
fulfills these requirements.

## Example Commit {#sec-guidelines-ex-commit-message}

The commit [69f8e47e9e74c8d3d060ca22e18246b7f7d988ef](https://github.com/nix-community/home-manager/commit/69f8e47e9e74c8d3d060ca22e18246b7f7d988ef)
in home-manager contains the following commit message.

```
starship: allow running in Emacs if vterm is used

The vterm buffer is backed by libvterm and can handle Starship prompts
without issues.
```

Similarly, if you are contributing to **nvf**, you would include the scope of
the commit followed by the description:

```
languages/ruby: init module

Adds a language module for Ruby, adds appropriate formatters and Treesitter grammers
```

Long description can be ommitted if the change is too simple to warrant it. A
minor fix in spelling or a formatting change does not warrant long description,
however, a module addition or removal does as you would like to provide the
relevant context, i.e. the reasoning behind it, for your commit.

Finally, when adding a new module, say `modules/foo.nix`, we use the fixed
commit format `foo: add module`. You can, of course, still include a long
description if you wish.

In case of nested modules, i.e `modules/languages/java.nix` you are recommended
to contain the parent as well - for example `languages/java: some major change`.

## Code Style {#sec-guidelines-code-style}

### Treewide {#sec-code-style-treewide}

Keep lines at a reasonable width, ideally 80 characters or less. This also applies
to string literals and module descriptions and documentation.

### Nix {#sec-code-style-nix}

**nvf** is formatted by the [alejandra](https://github.com/kamadorueda/alejandra)
tool and the formatting is checked in the pull request and push workflows. Run the
`nix fmt` command inside the project repository before submitting your pull request.

While Alejandra is mostly opinionated on how code looks after formatting,
certain changes are done at the user's discretion based on how the original
code was structured.

Please use one line code for attribute sets that contain only one subset.
For example:

```nix
# parent modules should always be unfolded
# which means module = { value = ... } instead of module.value = { ... }
module = {
  value = mkEnableOption "some description" // { default = true; }; # merges can be done inline where possible

    # same as parent modules, unfold submodules
    subModule = {
        # this is an option that contains more than one nested value
        someOtherValue = mkOption {
            type = lib.types.bool;
            description = "Some other description";
            default = true;
        };
    };
}
```

If you move a line down after the merge operator, Alejandra will automatically
unfold the whole merged attrset for you, which we **do not** want.

```nix
module = {
  key = mkEnableOption "some description" // {
    default = true; # we want this to be inline
  }; # ...
}
```

For lists, it is mostly up to your own discretion how you want to format them,
but please try to unfold lists if they contain multiple items and especially
if they are to include comments.

```nix
# this is ok
acceptableList = [
  item1 # comment
  item2
  item3 # some other comment
  item4
];

# this is not ok
listToBeAvoided = [item1 item2 /* comment */ item3 item4];

# this is ok
acceptableList = [item1 item2];

# this is also ok if the list is expected to contain more elements
acceptableList= [
  item1
  item2
  # more items if needed...
];
```