Block violations before commit

You want violations blocked locally before they’re committed, so a bad commit never even lands on your branch. This guide wires both checkers into pre-commit.

Install pre-commit

If you haven’t already:

pip install pre-commit
pre-commit install

Add the hook config

Drop this at the repo root as .pre-commit-config.yaml. Adjust the files: filters to match where your code lives: chisel_py / chisel_js below are chisel’s own monorepo dirs, rename them to your project.

.pre-commit-config.yaml

repos:
  - repo: local
    hooks:
      - id: chisel-py
        name: chisel (Python)
        entry: chisel check chisel_py --strict
        language: python
        language_version: python3.12
        additional_dependencies: [grimp>=3.0, radon>=6.0, typer>=0.12, rich>=13.0]
        files: ^chisel_py/src/.*\.py$
        pass_filenames: false

      - id: chisel-js
        name: chisel (TypeScript)
        entry: chisel-js check .
        language: system
        files: ^(chisel_js/src/.*\.ts|chisel_js/.*\.svelte)$
        pass_filenames: false

Use one hook or both depending on your stack: a pure-FastAPI repo only needs chisel-py; a pure-SvelteKit repo only needs chisel-js.

Install the CLIs the hooks call

pip install chisel                # for the chisel-py hook
npm install -g chisel-js          # for the chisel-js hook (or: bun add -g chisel-js)

Commit a chisel.config.json

Run chisel-js init once and commit the result:

chisel-js init .
git add chisel.config.json

This matters more for a hook than for an ad-hoc check. Without the config chisel-js re-detects the topology on every run, so a dependency change could quietly alter which rules gate your commits. Committing the file pins the mode and makes any change to it show up in review, like any other change.

Trigger

Every git commit now runs the hooks. They use pass_filenames: false because chisel scans the whole project, not individual files.

Why pass_filenames: false?

Chisel analyses the import graph of your entire project. Passing only the staged files would let a file pass because its dependencies weren’t in the staged set. Scanning the whole tree each run is what makes the determinism honest.

What’s next

• Run chisel in GitHub Actions: gate pull requests on the same check.
• Turn off a rule for a file: when a hook failure is a justified exception.