Some guidelines for people wanting to contribute. Also please always feel free to speak to us, we’re very friendly :-)

Feature additions

We welcome contributions in the form of bug fixes or feature additions. Please discuss with us before submitting anything, as we may well have some important context which will could help guide your efforts.

Any major feature additions should be raised first as a proposal on the BuildGrid mailing list to be discussed between the core contributors. Once this discussion has taken place and there is agreement on how to proceed, it should be followed by with a Gitlab issue being raised which summarizes the tasks required.

We strongly recommend that you propose the feature in advance of commencing any work.

The author of any patch is expected to take ownership of that code and is to support it for a reasonable time-frame. This means addressing any unforeseen side effects and quirks the feature may have introduced.

Patch submissions

Branches must be submitted as merge requests (MR) on GitLab and should have a corresponding issue raised in advance (whenever possible). If it’s a small change, an MR without it being associated to an issue is okay, but generally we prefer an issue to be raised in advance so that we can track the work that is currently in progress on the project.

When submitting a merge request, please obtain a review from another committer who is familiar with the area of the code base which the branch effects. Two approvals from other committers who are not the patch author will be needed before any merge (we use Gitlab’s ‘approval’ feature for this).

Below is a list of good patch submission good practice:

  • Each commit should address a specific issue number in the commit message. This is really important for provenance reasons.

  • Merge requests that are not yet ready for review should be prefixed with the Draft: identifier.

  • Submitted branches should not contain a history of work done.

  • Unit tests should be a separate commit.

Commit messages

Commit messages must be formatted with a brief summary line, optionally followed by an empty line and then a free form detailed description of the change. The summary line must start with what changed, followed by a colon and a very brief description of the change. If there is an associated issue, it must be mentioned somewhere in the commit message.

Example: Fixed to be more human than human

Gifted the worker with a past so we can create
a cushion or a pillow for their emotions and
consequently, we can control them better.

This fixes issue #8.

For more tips, please read The seven rules of a great Git commit message.

Coding style

Python coding style for BuildGrid is PEP 8. We do have a couple of minor exceptions to this standard, we dont want to compromise code readability by being overly restrictive on line length for instance.

BuildGrid’s test suite includes a PEP8 style compliance check using flake8. That test suite is automatically run for every change submitted to the GitLab server and the merge request sytem requires the test suite execution to succeed before changes can be pulled upstream. This means you have to respect the BuildGrid coding style. For convenience you can run tox -e flake8 to perform these checks.

BuildGrid’s CI also runs a static type check in the form of mypy. While mypy is stable, it is not yet 1.0 and thus is not able to understand every use case in typing (such as recursive types and complex mutators). Nevertheless, type annotations are strongly preferred for readability, with complex type issues flagged with # type: ignore.

Configuration and exceptions for flake8 can be found in:

Automated code formatting should be run using isort and black before submitting MRs to the project. These tools can be invoked by running tox -e format.


Both absolute and relative imports are allowed. Prefer absolute imports when possible, but if the absolute import path gets too long, relative imports are okay.


from buildgrid.worker import Worker


from .worker import Worker

Symbol naming

Any private symbol must start with a single leading underscore for two reasons:

  • So that it does not bleed into documentation and public API.

  • So that it is clear to developers which symbols are not used outside of the declaring scope.

Remember that with python, the modules (python files) are also symbols within their containing package, as such; modules which are entirely private to BuildGrid are named as such, e.g.


Always add type annotations to your code and ensure that mypy verifies it.

BuildGrid was started before we began adding type annotations to the codebase, so you may run across functions that are not annotated. If you do, please leave the functions better than you found them and add annotations. mypy was designed with this maintenance pattern in mind.


BuildGrid is using pytest for regression and newly added code testing. The test suite contains a serie of unit-tests and also run linting tools in order to detect coding-style breakage. The full test suite is automatically executed by GitLab CI system for every push to the server. Passing all the tests is a mandatory requirement for any merge request to the trunk.

Running tests

In order to run the entire test suite, simply run:

tox -e ci-venv -- pytest tests

pyest’s usage documentation section details the different command line options that can be used when invoking the test runner.

Test coverage

We are doing our best at keeping BuildGrid’s test coverage score as high as possible. Doing so, we ask for any merge request to include necessary test additions and/or modifications in order to maintain that coverage level. A detailed coverage report is produced and publish for any change merged to the trunk.

GitLab features

We intend to make use of some of GitLab’s features in order to structure the activity of the BuildGrid project. In doing so we are trying to achieve the following goals:

  • Full transparency of the current work in progress items

  • Provide a view of all current and planned activity which is relatively easy for the viewer to digest

  • Ensure that we keep it simple and easy to contribute to the project

Explanation of how the project is currenlty using some GitLab features:

  • Labels: allow us to filter tickets (ie, ‘issues’ in gitlab terminology) in useful ways. They add complexity and effort as they grow in number, so the general approach is to ensure the ones we have are actually used and are applied consistently. See the BuildGrid labels.

  • Boards: allow us to visualise and manage issues and labels in a simple way. Issues start life in the Backlog column by default, and we move them into ToDo when we aim to complete them in the current development cycle. Doing is only for when an item is currently being worked on. When on the Board view, dragging and dropping an issue from column to column automatically adjusts the relevant labels. See the BuildGrid boards.

Guidelines for using GitLab features when working on this project:

  • When raising an issue, please:

    • check to see if there already is an issue to cover this task (if not then raise a new one)

    • assign the appropriate label or labels (tip: the vast majority of issues raised will be either an enhancement or a bug)

  • If you plan to work on an issue, please:

    • self-assign the ticket

    • ensure the ticket is in the ToDo column of the board if you aim to complete in the current sprint but aren’t yet working on it, and the Doing column if you are working on it currently.

  • Please note that Gitlab issues are for either ‘tasks’ or ‘bugs’ - ie not for long discussions (where the mailing list is a better choice) or for ranting, for example.

The above may seem like a lot to take in, but please don’t worry about getting it right the first few times. The worst that can happen is that you’ll get a friendly message from a current contributor who explains the process. We welcome and value all contributions to the project!