Development guide

This page provides procedures and guidelines for developing and contributing to Safir.

Scope of contributions

Safir is an open source package, meaning that you can contribute to Safir itself, or fork Safir for your own purposes.

Since Safir is intended for internal use by Rubin Observatory, community contributions can only be accepted if they align with Rubin Observatory’s aims. For that reason, it’s a good idea to propose changes with a new GitHub issue before investing time in making a pull request.

Safir is developed by the LSST SQuaRE team.

Setting up a local development environment

To develop Safir, create a virtual environment with your method of choice (like virtualenvwrapper) and then clone or fork, and install:

git clone https://github.com/lsst-sqre/safir.git
cd safir
make init

This init step does three things:

  1. Installs Safir in an editable mode with its “dev” extra that includes test and documentation dependencies.

  2. Installs pre-commit and tox.

  3. Installs the pre-commit hooks.

You must have Docker installed and configured so that your user can start Docker containers in order to run the test suite.

Pre-commit hooks

The pre-commit hooks, which are automatically installed by running the make init command on set up, ensure that files are valid and properly formatted. Some pre-commit hooks automatically reformat code:

seed-isort-config

Adds configuration for isort to the pyproject.toml file.

isort

Automatically sorts imports in Python modules.

black

Automatically formats Python code.

blacken-docs

Automatically formats Python code in reStructuredText documentation and docstrings.

When these hooks fail, your Git commit will be aborted. To proceed, stage the new modifications and proceed with your Git commit.

Running tests

To test the library, run tox, which tests the library the same way that the CI workflow does:

tox run

To see a listing of test environments, run:

tox list

tox will start a PostgreSQL container, which is required for some tests.

To run a specific test or list of tests, you can add test file names (and any other pytest options) after -- when executing the py tox environment. For example:

tox run -e py -- tests/database_test.py

Building documentation

Documentation is built with Sphinx:

tox run -e docs

The build documentation is located in the docs/_build/html directory.

Updating the change log

Safir uses scriv to maintain its change log.

When preparing a pull request, run scriv create. This will create a change log fragment in changelog.d. Edit that fragment, removing the sections that do not apply and adding entries fo this pull request. You can pass the --edit flag to scriv create to open the created fragment automatically in an editor.

Change log entries use the following sections:

  • Backward-incompatible changes

  • New features

  • Bug fixes

  • Other changes (for minor, patch-level changes that are not bug fixes, such as logging formatting changes or updates to the documentation)

These entries will eventually be cut and pasted into the release description for the next release, so the Markdown for the change descriptions should be compatible with GitHub’s Markdown conventions for the release description. Specifically:

  • Each bullet point should be entirely on one line, even if it contains multiple sentences. This is an exception to the normal documentation convention of a newline after each sentence. Unfortunately, GitHub interprets those newlines as hard line breaks, so they would result in an ugly release description.

  • Avoid using too much complex markup, such as nested bullet lists, since the formatting in the GitHub release description may not be what you expect and manually editing it is tedious.

Style guide

Code

  • The code style follows PEP 8, though in practice lean on Black and isort to format the code for you.

  • Use PEP 484 type annotations. The tox run -e typing test environment, which runs mypy, ensures that the project’s types are consistent.

  • Write tests for Pytest.

Documentation