New code should be formatted using a linter

[DrPaulSharp]

Code Linting and Formatting using Ruff

Preamble

To ensure a consistent style of code throughout the SasView organization, we propose the use of a code linting tool to automatically run during the commit and pull request phases of development. Developers are further encouraged to make use of linting and formatting tools to identify and apply further fixes to aid code consistency.

Proposal

As part of the continuous integration process, an automated system should check the committed code and automatically make code edits based on a fixed set of rules. The rule set should be some subset of the PEP style guide and other such rulesets where automatic fixes are available. In addition, users should have access to a tool that they can use to check their code for violations of the rulesets that they can address locally. The suggested tools for this process are ruff and pre-commit.

Implementation on Github

• A pre-commit hook that gates CI if any automatically fixable linting issues are found in new code, corrects and commits necessary changes, and restarts the CI post-commit.
• A pre-commit hook that will activate on a developers system, assuming the developer system is set up properly. This hook will prevent a local commit if any automatically fixable linting errors are found.
• The hooks should use the ruff tool for making changes, using a pre-defined set of rules.
• All linting and formatting rules must be defined in the pyproject.toml.
• A repository owner must allow the pre-commit bot to make modifications on each repository this is enabled on.
• Pre-commit should be deployed on SasView, SasModels, and SasData. Any future code-based repositories (e.g. SasCalc if it created) should include pre-commit during their implementation phases.

Implementation on developer system

• ruff and pre-commit must be added to the requirement-dev.txt file to ensure developers' systems have the appropriate tools for use.
• Once the first step is finished, an announcement shall be made instructing all developers to update their Python environment using the latest requirements files, e.g. python -m uv pip install -r requirement.txt -r requirements-dev.txt --update
• All developers should ensure their environment is up to date.
• Developers using the local pre-commit hook should set it up using pre-commit install. This only needs to be done once.

Preferred usage

• New and existing developers should follow the procedure outlined in the Implementation on developer system.
• Prior to committing, developers should run both python -m ruff check --fix and python -m ruff format on any files modified. Any warnings that cannot be automatically fixed should be manually corrected by the developer.
• Developers are encouraged to fix existing linting errors in code other than that they have modified where they feel confident in doing so.
• Where a developer has made manual fixes, they should be committed with the commit message referring to ruff.
• For sections of code where formatting has not been applied, and doing so would modify a large number of lines of code, it is recommended that a developers put in a formatting pull request. This is a pull request where the only change to the code is running python -m ruff format on the set of files under consideration.

Linting Ruleset

The full set of rules that could be applied are outlined in https://docs.astral.sh/ruff/rules/

Initially Enforced

• Pycodestyle errors: https://docs.astral.sh/ruff/rules/#error-e
• Pyflake rules: https://docs.astral.sh/ruff/rules/#pyflakes-f
• Isort rules: https://docs.astral.sh/ruff/rules/#isort-i
• Pyupgrade rules: https://docs.astral.sh/ruff/rules/#pyupgrade-up
• Pycodestyle warnings: https://docs.astral.sh/ruff/rules/#warning-w
• SIM118 - Use key in dict instead of key in dict.keys(): https://docs.astral.sh/ruff/rules/in-dict-keys/
• SIM300 - Yoda condition detected: https://docs.astral.sh/ruff/rules/yoda-conditions/
• Line length: 120 characters

Initially Ignored

• E501 - Line too long - Formatter handles this
• UP008 - Use super() instead of super(__class__, self)
• UP031 - Use f"{value}" instead of "%s" % value

Revision Acceptance Date: 14th July 2026
Revision Number: 1
Original Suggestion: https://github.com/orgs/SasView/discussions/3171