Guidelines for contributing

Table of Contents

• Summary
• Git
• Python
  • Hatch
  • Testing with pytest
• Code quality
  • Running code quality checks
  • Code style
  • Static type checking
  • Spell check
• GitHub Actions workflows
• Maintainers

Summary

PRs welcome!

• Consider starting a discussion to see if there's interest in what you want to do.
• Submit PRs from feature branches on forks to the develop branch.
• Ensure PRs pass all CI checks.
• Maintain test coverage at 100%.

Git

• Why use Git? Git enables creation of multiple versions of a code repository called branches, with the ability to track and undo changes in detail.
• Install Git by downloading from the website, or with a package manager like Homebrew.
• Configure Git to connect to GitHub with SSH.
• Fork this repo.
• Create a branch in your fork.
• Commit your changes with a properly-formatted Git commit message.
• Create a pull request (PR) to incorporate your changes into the upstream project you forked.

Hatch

This project uses Hatch for dependency management and packaging.

Highlights

• Automatic virtual environment management: Hatch automatically manages the application environment.
• Dependency resolution: Hatch will automatically resolve any dependency version conflicts using the pip dependency resolver.
• Dependency separation: Hatch supports separate lists of optional dependencies in the pyproject.toml. Production installs can skip optional dependencies for speed.
• Builds: Hatch has features for easily building the project into a Python package and publishing the package to PyPI.

Installation

Hatch can be installed with Homebrew or pipx.

Install project with all dependencies: hatch env create.

Key commands

# Basic usage: https://hatch.pypa.io/latest/cli/reference/
hatch env create  # create virtual environment and install dependencies
hatch env find  # show path to virtual environment
hatch env show  # show info about available virtual environments
hatch run COMMAND  # run a command within the virtual environment
hatch shell  # activate the virtual environment, like source venv/bin/activate
hatch version  # list or update version of this package
export HATCH_ENV_TYPE_VIRTUAL_PATH=.venv  # install virtualenvs into .venv

Testing with pytest

• Tests are in the tests/ directory.
• pytest features used include:
  • capturing stdout with capfd
  • fixtures
  • monkeypatch
  • parametrize
  • temporary directories and files (tmp_path and tmp_dir)
• pytest plugins include:
  • pytest-mock
• pytest configuration is in pyproject.toml.
• Run tests with pytest and coverage.py with hatch run coverage run.
• Test coverage reports are generated by coverage.py. To generate test coverage reports:
  1. Run tests with hatch run coverage run
  2. Generate a report with coverage report. To see interactive HTML coverage reports, run coverage html instead of coverage report.

Code quality

Running code quality checks

Code quality checks can be run using the Hatch scripts in pyproject.toml.

• Check: hatch run check
• Format: hatch run format

Code style

• Python code is formatted with Ruff. Ruff configuration is stored in pyproject.toml.
• Other web code (JSON, Markdown, YAML) is formatted with Prettier.

Static type checking

• To learn type annotation basics, see the Python typing module docs, Python type annotations how-to, the Real Python type checking tutorial, and this gist.
• Type annotations are not used at runtime. The standard library typing module includes a TYPE_CHECKING constant that is False at runtime, but True when conducting static type checking prior to runtime. Type imports are included under if TYPE_CHECKING: conditions so that they are not imported at runtime. These conditions are ignored when calculating test coverage.
• Type annotations can be provided inline or in separate stub files. Much of the Python standard library is annotated with stubs. For example, the Python standard library logging.config module uses type stubs. The typeshed types for the logging.config module are used solely for type-checking usage of the logging.config module itself. They cannot be imported and used to type annotate other modules.
• The standard library typing module includes a NoReturn type. This would seem useful for unreachable code, including functions that do not return a value, such as test functions. Unfortunately mypy reports an error when using NoReturn, "Implicit return in function which does not return (misc)." To avoid headaches from the opaque "misc" category of mypy errors, these functions are annotated as returning None.
• Mypy is used for type-checking. Mypy configuration is included in pyproject.toml.
• Mypy strict mode is enabled. Strict includes --no-explicit-reexport (implicit_reexport = false), which means that objects imported into a module will not be re-exported for import into other modules. Imports can be made into explicit exports with the syntax from module import x as x (i.e., changing from import logging to import logging as logging), or by including imports in __all__. This explicit import syntax can be confusing. Another option is to apply mypy overrides to any modules that need to leverage implicit exports.

Spell check

Spell check is performed with CSpell. The CSpell command is included in the Hatch script for code quality checks (hatch run check).

GitHub Actions workflows

GitHub Actions is a continuous integration/continuous deployment (CI/CD) service that runs on GitHub repos. It replaces other services like Travis CI. Actions are grouped into workflows and stored in .github/workflows. See Getting the Gist of GitHub Actions for more info.

Maintainers

• The default branch is develop.
• PRs should be merged into develop. Head branches are deleted automatically after PRs are merged.
• The only merges to main should be fast-forward merges from develop.
• Branch protection is enabled on develop and main.
  • develop:
    • Require signed commits
    • Include administrators
    • Allow force pushes
  • main:
    • Require signed commits
    • Include administrators
    • Do not allow force pushes
    • Require status checks to pass before merging (commits must have previously been pushed to develop and passed all checks)
• To create a release:
  • Bump the version number in __version__ with hatch version and commit the changes to develop.
    • Follow SemVer guidelines when choosing a version number. Note that PEP 440 Python version specifiers and SemVer version specifiers differ, particularly with regard to specifying prereleases. Use syntax compatible with both.
    • The PEP 440 default (like 1.0.0a0) is different from SemVer. Hatch and PyPI will use this syntax by default.
    • An alternative form of the Python prerelease syntax permitted in PEP 440 (like 1.0.0-alpha.0) is compatible with SemVer, and this form should be used when tagging releases. As Hatch uses PEP 440 syntax by default, prerelease versions need to be written directly into __version__.
    • Examples of acceptable tag names: 1.0.0, 1.0.0-alpha.0, 1.0.0-beta.1
  • Push to develop and verify all CI checks pass.
  • Fast-forward merge to main, push, and verify all CI checks pass.
  • Create an annotated and signed Git tag.
    • List PRs and commits in the tag message:

      git log --pretty=format:"- %s (%h)" \
        "$(git describe --abbrev=0 --tags)"..HEAD

    • Omit the leading v (use 1.0.0 instead of v1.0.0)
    • Example: git tag -a -s 1.0.0
  • Push the tag. GitHub Actions will build and publish the Python package.
• Consider keeping a changelog. There are many tools and approaches for this. Most of them work like this:
  1. Accumulate "fragments" as the project is developed. These could be text files in a directory under version control, or could also be Git commit/PR/tag messages. Fragments should contain human-readable summaries of code changes.
  2. Collect the fragments and combine them into a text file like CHANGELOG.md.