elvish/CONTRIBUTING.md

Contributor's Manual

Human communication

The project lead is @xiaq, who is reachable in the user group most of the time.

If you intend to make user-visible changes to Elvish's behavior, it is good idea to talk to him first; this will make it easier to review your changes.

On the other hand, if you find it easier to express your thoughts directly in code, it is also completely fine to directly send a pull request, as long as you don't mind the risk of the PR being rejected due to lack of prior discussion.

Using development scripts

The Makefile contains targets encapsulating some common workflows. They are not necessary for developing Elvish, but can save you a few keystrokes. GNU Make is required.

The tools directory contains scripts too complex to fit in the Makefile. Among them, tools/pre-push can be used as a Git hook, and covers a large subset (but not all) of CI checks.

Testing changes

Write comprehensive unit tests for your code, and make sure that existing tests are passing. Tests are run on CI automatically for PRs; you can also run make test in the repo root yourself.

Respect established patterns of how unit tests are written. Some packages unfortunately have competing patterns, which usually reflects a still-evolving idea of how to best test the code. Worse, parts of the codebase are poorly tested, or even untestable. In either case, discuss with the project lead on the best way forward.

ELVISH_TEST_TIME_SCALE

Some unit tests depend on time thresholds. The default values of these time thresholds are suitable for a reasonably powerful laptop, but on resource-constraint environments (virtual machines, embedded systems) they might not be enough.

Set the ELVISH_TEST_TIME_SCALE environment variable to a number greater than 1 to scale up the time thresholds used in tests. The CI environments use ELVISH_TEST_TIME_SCALE = 10.

Documenting changes

Always document user-visible changes.

Release notes

Add a brief list item to the release note of the next release, in the appropriate section. You can find the document at the root of the repo (called $version-release-notes.md).

Reference docs

Reference docs are interspersed in Go sources as comments blocks whose first line starts with //elvdoc (and are hence called elvdocs). They can use Github Flavored Markdown.

Elvdocs for functions look like the following:

//elvdoc:fn name-of-fn
//
// ```elvish
// name-of-fn $arg &opt=default
// ```
//
// Does something.
//
// Example:
//
// ```elvish-transcript
// ~> name-of-fn something
// ▶ some-value-output
// ```

func nameOfFn() { ... }

Generally, elvdocs for functions have the following structure:

• A line starting with //elvdoc:fn, followed by the name of the function. Note that there should be no space after //, unlike all the other lines.

• An elvish code block describing the signature of the function, following the convention here.

• Description of the function, which can be one or more paragraphs. The first sentence of the description should start with a verb in 3rd person singular (i.e. ending with a "s"), as if there is an implicit subject "this function".

• One or more elvish-transcript code blocks showing example usages, which are transcripts of actual REPL input and output. Transcripts must use the default prompt ~> and default value output indicator ▶. You can use elvish -norc if you have customized either in your rc.elv.

Place the comment block before the implementation of the function. If the function has no implementation (e.g. it is a simple wrapper of a function from the Go standard library), place it before the top-level declaration of the namespace.

Similarly, reference docs for variables start with //elvdoc:var:

//elvdoc:var name-of-var
//
// Something.

Variables do not have signatures, and are described using a noun phrase. Examples are not always needed; if they are, they can be given in the same format as examples for functions.

Comment for unexported Go types and functions

In the doc comment for exported types and functions, it's customary to use the symbol itself as the first word of the comment. For unexported types and functions, this becomes a bit awkward as their names don't start with a capital letter, so don't repeat the symbol. Examples:

// Foo does foo.
func Foo() { }

// Does foo.
func foo() { }

Generating code

Elvish uses generated code in a few places. As is the usual case with Go projects, they are committed into the repo, and if you change the input of a generated file you should re-generate it.

Use the standard command, go generate ./... to regenerate all files.

Some of the generation rules depend on the stringer tool. Install with go install golang.org/x/tools/cmd/stringer@latest.

Code hygiene

Some basic aspects of code hygiene are checked in the CI.

Formatting

Install goimports to format Go files, and prettier to format Markdown files.

go install golang.org/x/tools/cmd/goimports@latest
npm install --global prettier@2.7.1

Once you have installed the tools, use make style to format Go and Markdown files. If you prefer, you can also configure your editor to run these commands automatically when saving Go or Markdown sources.

Use make checkstyle to check if all Go and Markdown files are properly formatted.

Linting

Install staticcheck:

go install honnef.co/go/tools/cmd/staticcheck@v0.3.2

The other linter Elvish uses is the standard go vet command. Elvish doesn't use golint since it is deprecated and frozen.

Use make lint to run staticcheck and go vet.

Spell checking

Install codespell to check spelling:

pip install --user codespell==2.2.1

Use make codespell to run it.

Running all checks

Use this command to run all checks:

make test checkstyle lint codespell

You can put this in .git/hooks/pre-push to ensure that your published commits pass all the checks.

Licensing

By contributing, you agree to license your code under the same license as existing source code of elvish. See the LICENSE file.