Lint and hooks¶

lint.yml runs on every pull request and every push to master, and .githooks/pre-commit runs the same checks locally, so the two cannot disagree.

Check	What it lints	Rules
`ruff check .`	the Python files	`.ruff.toml`
`eslint`	the `.js` and `.jsx` files under `jsx/`	`jsx/eslint.config.mjs`

Correctness only¶

The ruff rule set is deliberately correctness-only (E4, E7, E9, F, W6): syntax errors, undefined names, unused imports and variables, bare except, invalid escape sequences. No formatting, import-ordering or type-annotation rules are enabled, so a red build always means a real defect rather than a style preference. Notebooks are excluded; several carry pasted tabular output inside code cells and are not parseable Python.

The ESLint config follows the same philosophy: no-undef, no-unused-vars, no-dupe-keys, no-unreachable, no-cond-assign and similar. No semicolon, quote, indentation or spacing rules. Two settings are worth knowing about:

eslint-plugin-react is required, not cosmetic. The application uses the classic JSX transform, so <Foo /> compiles to React.createElement(Foo). Core ESLint does not treat JSX as a use of an identifier, so without the plugin's jsx-uses-react and jsx-uses-vars rules, no-unused-vars reports every imported component -- React included -- as unused.
no-redeclare is deliberately off. It fires on a legacy pattern used throughout the codebase: a function-scoped var "redeclared" inside if and else branches. That behaves exactly as written, so it is a style complaint rather than a defect.

The ruff version is pinned in the workflow, so a new upstream release cannot redden an untouched branch; bump it deliberately. ESLint 9 needs Node ^18.18 || ^20.9 || >=21.1, and the workflow pins Node 20.

Running it by hand¶

pip install ruff==0.16.1
ruff check .
cd jsx && npm install && npx eslint .

The hooks¶

Enable both hooks once per clone:

git config core.hooksPath .githooks

pre-commit checks the staged files. It rejects invisible and confusable Unicode and anything shaped like a committed secret -- both checks are standard-library Python, so a fresh clone is protected with nothing installed -- and lints staged Python with ruff and staged JavaScript with ESLint.

A missing linter is a hard failure, not a skip. A lint that silently opts out on the machines lacking the tool passes locally and then fails in CI on a commit already pushed; see #24. ruff is looked for in the project's .venv before PATH, and ESLint needs Node 18.18 or newer. To bypass the hook entirely, commit with --no-verify.

pre-push, in .githooks/pre-push, refuses a push to master. Every merge comes through a pull request; work goes on a feature-<issue> branch.