Pybites Rust Cohort: A minimal pre-commit hook

.pre-commit-config.yaml

repos:
  - repo: local
    hooks:
      - id: cargo-fmt
        name: cargo fmt
        entry: cargo fmt --manifest-path rust-json-parser/Cargo.toml --
        language: system
        types: [rust]
        pass_filenames: false

      - id: cargo-clippy
        name: cargo clippy
        entry: cargo clippy --manifest-path rust-json-parser/Cargo.toml -- -D warnings
        language: system
        types: [rust]
        pass_filenames: false

README-pre-commit-hook.md

Pre-commit Hooks for Rust Projects

Automatically run cargo fmt and cargo clippy before every commit. Catches issues before they reach the repo.

Why Use Pre-commit Hooks?

• Automatic formatting - Never commit unformatted code
• Catch issues early - Clippy warnings caught before commit
• Team consistency - Everyone's code meets the same standards
• No CI surprises - If it commits, it passes checks

Prerequisites

Install pre-commit (Python tool):

# macOS
brew install pre-commit

# pip
pip install pre-commit

The Config File

Create .pre-commit-config.yaml in your project root:

repos:
  - repo: local
    hooks:
      - id: cargo-fmt
        name: cargo fmt
        entry: cargo fmt --manifest-path rust-json-parser/Cargo.toml --
        language: system
        types: [rust]
        pass_filenames: false

      - id: cargo-clippy
        name: cargo clippy
        entry: cargo clippy --manifest-path rust-json-parser/Cargo.toml -- -D warnings
        language: system
        types: [rust]
        pass_filenames: false

Setup

# Install the hooks (run once per repo clone)
pre-commit install

# Or use make if you have the Makefile
make pre-commit-install

How It Works

After setup, every git commit will:

1. Run cargo fmt - formats any changed Rust files
2. Run cargo clippy - checks for warnings/errors
3. If either fails, commit is blocked

$ git commit -m "Add feature"
cargo fmt................................................................Passed
cargo clippy.............................................................Passed
[main abc1234] Add feature

If a Hook Fails

$ git commit -m "Add feature"
cargo fmt................................................................Failed
- hook id: cargo-fmt
- files were modified by this hook

# fmt modified files, need to re-stage and commit again
$ git add .
$ git commit -m "Add feature"

Config Explained

Field	Purpose
repo: local	Use local commands (not remote hook repos)
entry	The command to run
--manifest-path	Points to Cargo.toml location
language: system	Use system-installed cargo
types: [rust]	Only run on .rs files
pass_filenames: false	Run on whole project, not individual files

Useful Commands

# Run hooks manually (without committing)
pre-commit run --all-files

# Skip hooks for one commit (use sparingly!)
git commit --no-verify -m "WIP"

# Update hooks
pre-commit autoupdate

Adapting for Your Project

If your Cargo.toml is in the root (not a subdirectory), simplify to:

repos:
  - repo: local
    hooks:
      - id: cargo-fmt
        name: cargo fmt
        entry: cargo fmt --
        language: system
        types: [rust]
        pass_filenames: false

      - id: cargo-clippy
        name: cargo clippy
        entry: cargo clippy -- -D warnings
        language: system
        types: [rust]
        pass_filenames: false