CONTRIBUTING.md

Contributing to bilby

This is a short guide to help get you started contributing to bilby.

Getting started

All the code lives in a git repository (for a short introduction to git, see this tutorial) which is hosted here: https://git.ligo.org/lscsoft/bilby. If you haven't already, you should fork the repository and clone your fork, i.e., on your local machine run

$ git clone git@git.ligo.org:albert.einstein/bilby.git

replacing the SSH url to that of your fork. This will create a directory /bilby containing a local copy of the code. From this directory, you can run

$ python setup.py develop

which will install bilby and, because we used develop instead of install when you change the code your installed version will automatically be updated.

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Removing previously installed versions

If you have previously installed bilby using pip (or generally find buggy behaviour), it may be worthwhile purging your system and reinstalling. To do this, first find out where the module is being imported from: from any directory that is not the source directory, do the following

$ python
>>> import bilby
>>> print(bilby.__file__)
/home/user/anaconda2/lib/python2.7/site-packages/bilby-0.2.2-py2.7.egg/bilby/__init__.pyc

In the example output above, we see that the directory that module is installed in. To purge our python installation, run

$ rm -r /home/user/anaconda2/lib/python2.7/site-packages/bilby*

You can then verify this was successful by trying to import bilby in the python interpreter.

Discussion

If you've run into behavior you don't understand, or you're having trouble working out a good way to apply it to your code, or you've found a bug or would like a feature it doesn't have, we want to hear from you!

Our main forum for discussion is the project's GitLab issue tracker. This is the right place to start a discussion of any of the above or most any other topic concerning the project.

Code of Conduct

Everyone participating in the bilby community, and in particular in our issue tracker, merge requests, and IRC channel, is expected to treat other people with respect and more generally to follow the guidelines articulated in the Python Community Code of Conduct.

Submitting Changes

All changes to the code base go through the merge-request workflow Anyone may review your code and you may expect a few comments and questions. Once all discussions are resolved, core developers will approve the merge request and then merge in into master. If you go a few days without a reply, please feel free to ping the thread by adding a new comment.

All merge requests should be focused: they should aim to either add one feature, solve one bug, or fix some stylistic issues. If multiple changes are lumped together it can slow down the process and make it harder to review.

Before you begin: if your change will be a significant amount of work to write, we highly recommend starting by opening an issue laying out what you want to do. That lets a conversation happen early in case other contributors disagree with what you'd like to do or have ideas that will help you do it.

We are keen to maintain a high standard of the code. This makes it easier to maintain, develop, and track down buggy behaviour.

All merge requests should also be recorded in the CHANGELOG.md. This just requires a short sentence describing describing the change, e.g., "- Enable initial values for emcee to be specified."

Updating your fork

If you already have a fork of bilby, and are starting work on a new project you can link your clone to the main (lscsoft) repository and pull in changes that have been merged since the time you created your fork, or last updated:

1. Link your fork to the main repository:

From the directory /bilby containing a local copy of the code:

$ git remote add lscsoft https://git.ligo.org/lscsoft/bilby

2. Fetch new changes from the lscsoft repo

$ git fetch lscsoft

Creating a new feature branch

All changes should be developed on a feature branch, in order to keep them separate from other work, simplifying review and merge once the work is done.

To create a new feature branch:

$ git fetch lscsoft
$ git checkout -b my-new-feature lscsoft/master

Hack away

1. Develop the changes you would like to introduce, using git commit to finalise a specific change. Ideally commit small units of change often, rather than creating one large commit at the end, this will simplify review and make modifying any changes easier.

   Commit messages should be clear, identifying which code was changed, and why. Common practice is to use a short summary line (<50 characters), followed by a blank line, then more information in longer lines.

2. Push your changes to the remote copy of your fork on git.ligo.org

git push origin my-new-feature

Note: For the first push of any new feature branch, you will likely have to use the -u/--set-upstream option to push to create a link between your new branch and the origin remote:

git push --set-upstream origin my-new-feature

Open a Merge Request

When you feel that your work is finished, or if you want feedback on it, you should create a Merge Request to propose that your changes be merged into the main (lscsoft) repository.

After you have pushed your new feature branch to origin, you should find a new button on the bilby repository home page inviting you to create a Merge Request out of your newly pushed branch. You should click the button, and proceed to fill in the title and description boxes on the MR page. If you are still working on the merge request and don’t want it to be merged accidentally, add the string "wip", "work in progress" or "do not merge" (not case-sensitive), to the title.

Once the request has been opened, one of the maintainers will assign someone to review the change.

ADD DISCUSSION ON CODE QUALITY

Reviewing Changes

If you are reviewing a merge request (either as a core developer or just as an interested party) please key these three things in mind

• If you open a discussion, be timely in responding to the submitter. Note, the reverse does not need to apply.
• Keep your questions/comments focused on the scope of the merge request. If while reviewing the code you notice other things which could be improved, open a new issue.
• Be supportive - merge requests represent a lot of hard work and effort and should be encouraged.

Core developer guidelines

Core developers should follow these rules when processing merge requests:

• Always wait for tests to pass before merging MRs.
• Delete branches for merged MRs (by core devs pushing to the main repo).
• Make sure related issues are linked and (if appropriate) closed.
• Squash commits

Issue-tracker conventions

Bug reporting

If you notice any bugs in the code, please let us know!

Issues reporting bugs should include:

• A brief description of the issue.
• A full error trace (if applicable).
• A minimal example to reproduce the issue.

Feature requests

If there's any additional functionality you'd like to see in the code open an issue describing the desired feature.

In order to maximise the likelihood that feature requests will be fulfilled you should:

• Make the feature request as specific as possible, vague requests are unlikely to be taken on by users.
• If possible break down the feature into small chunks which can be marked off on a checklist.

Code overview

In this section, we'll give an overview of how the code is structured. This is intended to help orient users and make it easier to contribute. The layout is intended to define the logic of the code and new merge requests should aim to fit within this logic (unless there is a good argument to change it). For example, code which adds a new sampler should not effect the gravitational-wave specific parts of the code. Note that this document is not programatically generated and so may get out of date with time. If you notice something wrong, please open an issue.

Bilby Code Layout

Note this layout is not comprehensive, for example only a few example "Priors" are shown.