Linting

Table of contents

  1. Where the configuration lives
  2. Check Python syntax
  3. Auto-fix Python code style
  4. Using flake8 directly
  5. What CI runs

Where the configuration lives

There is no .flake8 file and no setup.cfg. Every tool reads the root pyproject.toml:

[tool.black]
line-length = 120
target-version = ["py313"]

[tool.isort]
line_length = 120
profile = "black"

[tool.flake8]
max-line-length = 120
extend-ignore = ["E203", "W503"]

flake8 has no native support for pyproject.toml. The Flake8-pyproject plugin, pinned in requirements.txt, is what teaches it to read the [tool.flake8] table. It is installed with the rest of the dependencies, so you do not need to do anything extra.

Check Python syntax 

rosemary linter

This runs Flake8 over the app and rosemary directories, one at a time, and reports whether each one is clean. Both target directories are resolved against WORKING_DIR, and the command passes no --config flag: Flake8-pyproject discovers the [tool.flake8] table in pyproject.toml on its own, so rosemary linter works from any directory.

If flake8 finds issues in either directory, rosemary linter reports them and exits with a non-zero status, so the command can be used as a gate in a script or a pre-commit hook. When both directories are clean it exits 0.

Auto-fix Python code style 

rosemary linter:fix

This rewrites the files in app and rosemary in place, applying three tools in order:

  1. autoflake removes unused imports and unused variables, recursively.
  2. isort sorts the imports.
  3. black --line-length=120 formats the code.

Run it before committing. Most of what rosemary linter complains about is fixed by this command.

Using flake8 directly

You can also call the tools yourself from the project root:

flake8 app rosemary

Thanks to Flake8-pyproject, this picks up [tool.flake8] from pyproject.toml without any extra flag.

The equivalent checks for the formatters, which report problems without modifying anything:

black --check app rosemary
isort --check-only app rosemary

What CI runs

The Python Lint workflow (.github/workflows/CI_lint.yml) runs on every push and every pull request. It sets up Python 3.13 and then executes exactly the three commands above:

flake8 app rosemary
black --check app rosemary
isort --check-only app rosemary

If those three pass locally, the lint job will pass too.