Pre-commit hooks let you run checks before allowing a commit (e.g. JSLint or Test Coverage).
Think of pre-commit as an automatic checklist for your code. The checks prevents people from committing code that does not meet the required standards, saving everyone time. Imagine never having to read sloppy code again...!
Git Hooks are a a way to fire off custom scripts when certain important actions occur. e.g: commit, push, and merge. There are two groups of these hooks: client side and server side. The client-side hooks are for client operations such as committing and merging. The server-side hooks are for Git server operations such as automatically starting the build/test server or notifying team-mates of changes.
You can use these hooks for all sorts of reasons, we are going to focus on client-side pre-commit hooks (checks that are run before code is allowed to be committed).
- Code Consistency (Lint)
- Code Style (e.g. )
- All Unit Tests Pass
- Code Coverage standards met (100%)
- Performance tests / benchmarks met.
- Security Checks pass.
In node-land there are two popular modules we can use to run pre-commit checks:
- precommit-hook: https://www.npmjs.org/package/precommit-hook
- pre-commit: https://www.npmjs.org/package/pre-commit
Both are functionally equivalent so take your pick.
I'm covering pre-commit
because has more concise documentation.
Install the node module and save it as a development dependency for your project:
npm install pre-commit --save-dev
Example package.json file:
{
"name": "learn-pre-commit",
"version": "1.0.0",
"description": "Node.js pre-commit tutorial",
"repository": {
"type": "git",
"url": "https://github.com/nelsonic/learn-pre-commit"
},
"devDependencies": {
"istanbul": "^0.3.2",
"pre-commit": "0.0.9",
"tape": "^3.0.1"
},
"scripts": {
"test": "tape ./test/*.js",
"coverage": "istanbul cover tape ./test/*.js && istanbul check-coverage --statements 100 --functions 100 --lines 100 --branches 100",
"jshint": "jshint -c .jshintrc --exclude-path .gitignore .",
},
"pre-commit": [
"jshint",
"coverage"
]
}The interesting bits here are:
a) scripts - a list tasks that can be run.
Each script can be run by issuing the command:
npm run script-name (e.g: npm run coverage to check the test coverage).
b) pre-commit - an array of the scripts we want to run (in order) before we allow a commit. In this case jshint ensures our code is consistent according to the rules for the project and coverage ensures that our desired level of code/test coverage (100%) is met.
See /example for a Hello World example.
Try it in your own porjects! If you have any questions, submit an issue on GitHub or tweet me @nelsonic
- Gentle introduction to Git Hooks: http://githooks.com
- Way more than you will ever need to know about Git Hooks: http://git-scm.com/book/en/Customizing-Git-Git-Hooks (the official Git guide to Hooks)
### Code Style
- Addy Osmani on Code Style: http://addyosmani.com/blog/javascript-style-guides-and-beautifiers
- JavaScript Code Style checker (NPM) module: https://www.npmjs.org/package/jscs
- How do we define Code Quality? http://stackoverflow.com/questions/405243/how-do-we-define-code-quality (interesting discussion. mostly opinion - I want an objective measure!)
- Software Quality (in depth): http://en.wikipedia.org/wiki/Software_quality
- ISO/IEC 9126 Software engineering — Product quality: http://en.wikipedia.org/wiki/ISO/IEC_9126 (old but human-readable!)
- Full ISO/IEC 25010 Software Quality Standard (current): https://www.iso.org/obp/ui/#iso:std:iso-iec:25010:ed-1:v1:en (tldr;)
We haven't (yet) found a good way of doing pre-commit checks
in Java.
Our Java Team are using sonar
to run code quality checks. (sadly, this is not pre-commit!)
For Ruby & Python checkout pre-commit.com (its multi-language)
If you find a better pre-commit tool for Java-land, please inform me or send a PR!