Contributing - oilshell/oil GitHub Wiki

NOTE: If anything on this page doesn't work for you, please file a bug!

(Related: Oil Native Quick Start / Where Contributors Have Problems / Oil Dev Cheat Sheet / Oil Dev Tips / Making Pull Requests)


You should use Linux to make changes to OSH and test them. One reason for this is that the spec tests run against four other shells (bash/dash/zsh/mksh), and we don't have a way of building the right versions of these shells on other OSes.

When I'm on a Mac, I use Ubuntu on Virtualbox to develop.

  • Note that OSH does work on OS X for end users, but development is a different story.
  • 3/2020 update: there's a shell.nix in the root of the repo that may work on OS X. Ping us on Zulip if you need help with it. (Developing Oil With Nix)

Note on cloning oilshell/oil vs. creating a fork

Right now we have some awkwardness due to CI permissions.

We want you to send PRs from oilshell/oil and not your own fork, so that Github Actions can get our $TOIL_KEY, and publish HTML results to .

But this is a hiccup for first time contributors. I have to add you to the Github project so the CI can run. Ping me on Zulip!

Build Two Complete Oils Interpreters: in Python and in C++ (5-10 minutes)

This is the standard dev setup, which involves building tools like re2c, Python 3, and MyPy:

git clone    # please use this repo, not your own fork
                                                 # this helps us use a Github Action secret on PRs

cd oil                    # enter the base directory

build/ ubuntu-deps   # Works on Debian or Ubuntu -- uses sudo apt-get
                          # These are apt packages needed to build Python 2 and 3 from scratch ("wedges")

build/ fetch       # Download a bunch of source tarballs
build/install-wedges-fast # Build and install in parallel

build/ all           # Generates Python code - (re2c for lexer, CommonMark for help, etc.)

bin/osh -c 'echo hi'      # Sanity check to make sure it works.

Every time you git pull, you may need to repeat the last step:

git pull
build/ all        
bin/osh -c 'echo hi' 

In case you get in trouble:

build/              # deletes all the temp files in the repo
build/ rm-oils-crap  # deletes the build "wedges" outside the repo
                            # this is just rm -rf ~/wedge /wedge - latter requires root permissions

TODO: Clickable demo in gitpod or some other online dev env.

Quick Start with "minimal" build (~2 minutes)

This can be a quicker way to get started. It works only works if you already python2 on your machine (python2 being deprecated, of course).

git clone 

cd oil 

build/ ubuntu-deps
build/ minimal       # MINIMAL dev build, including native/libc.c Python extension

bin/osh -c 'echo hi' 

This is all you need to make many changes to Oils.

Quick Tests

test/ unit frontend/     # Run an individual unit test
test/ all          # run most unit tests, takes about a second or two

test/ smoke        # run a single file; there are more but this is a good start
test/ ysh-all      # all YSH tests

See Spec Tests for details.

Cheat Sheet

See Oil Dev Cheat Sheet for a summary of the commands above.

And tips on running more tests and benchmarks.

Other Test Suites

There are many other test suites which are reported on:

  1. The /release/$VERSION/quality.html page on every release
  2. The "Soil" continuous build at

For example, you can run

test/ all

To see a big demonstration of parse errors. I use this to supplement the spec tests when changing the syntax of the language.

Working on C++: oils-cpp

If you did the above, then the Python bin/osh should be working.

If you want to work on C++, then you should get _bin/cxx-asan/osh to work. See Oil Native Quick Start, which links to the mycpp

Tips for Developing

  • Make sure to build/ minimal (or all) after you git pull ! The Python extension modules (.so files) that OSH uses may be out of date, and they have to match the Python code.
  • Use build/ to start over.
    • It deletes all the temp files created by the tools, in underscore dirs like _build and _tmp.
    • See Oil Dev Cheat Sheet
  • Spec Tests are very important! Make sure you know how to run them quickly and maintain a fast, iterative development style.
    • Where Do I Put Spec Tests? If I'm going to change the behavior of the source builtin, I do grep source spec/* and that leads to the spec test that should verify the new behavior.
  • Debugging Completion Scripts -- Use --debug-file!

Pull Requests

Most people use Github pull requests to send patches. I will use Github's system to make comments. After addressing them, please:

  1. push the commits so I can see them
  2. reply with a message, like "All done", or "I disagree because ..."

If you only push commits, I won't look at the PR again, because I'll assume it's in progress.

I aim for 24-hour response time

Please feel free to ping andychu on Zulip or Github if you're waiting for a pull request review! (or to ask questions)

Usually I can respond in 24 hours. I might be traveling, in which case I'll respond with something like I hope to look at this by Tuesday.

I might have also missed your Github message, so it doesn't hurt to ping me.

Thank you for the contributions!

Code Style

Python code follows PEP 8, with some modifications from Google's Python style guide, like CapWords() for function names.

  • For shell code, also follow the existing style. It has 2 space indents, funcs-like-this (unless POSIX shell is required), and vars_like_this.
  • C code generally follows the style that CPython uses (except 2 space indents?)

Code Overviews