validate-commit-msg.js

#!/usr/bin/env node

/**
 * Git COMMIT-MSG hook for validating commit message
 * See https://docs.google.com/document/d/1rk04jEuGfk9kYzfqCuOlPTSJw3hEDZJTBN5E5f1SALo/edit
 *
 * Installation:
 * >> cd <repo>
 * >> ln -s ../../validate-commit-msg.js .git/hooks/commit-msg
 */
var fs = require('fs')
var util = require('util')
var path = require('path')

var MAX_LENGTH = 100
var PATTERN = /^(\w*)(\(([\w\$\.\-\*]*)\))?\: (.*)$/
var IGNORED = /^(WIP\:|Merge pull request)/
var TYPES = {
  feat: true,
  fix: true,
  docs: true,
  style: true,
  refactor: true,
  test: true,
  chore: true
}

var error = function () {
  // gitx does not display it
  // https://groups.google.com/group/gitx/browse_thread/thread/a03bcab60844b812
  console.error('INVALID COMMIT MSG: ' + util.format.apply(null, arguments))
}

var validateMessage = function (message) {
  var isValid = true

  if (IGNORED.test(message)) {
    console.log('Commit message validation ignored.')
    return true
  }

  if (message.length > MAX_LENGTH) {
    error('is longer than %d characters !', MAX_LENGTH)
    isValid = false
  }

  var match = PATTERN.exec(message)

  if (!match) {
    error('does not match "<type>(<scope>): <subject>" !')
    return false
  }

  var type = match[1]

  if (!TYPES.hasOwnProperty(type)) {
    error('"%s" is not allowed type !\n  Valid <type> values are: %s', type,
        Object.keys(TYPES).join(', '))
    return false
  }

  // Some more ideas, do want anything like this ?
  // - allow only specific scopes (eg. fix(docs) should not be allowed ?
  // - auto correct the type to lower case ?
  // - auto correct first letter of the subject to lower case ?
  // - auto add empty line after subject ?
  // - auto remove empty () ?
  // - auto correct typos in type ?
  // - store incorrect messages, so that we can learn

  return isValid
}

var firstLineFromBuffer = function (buffer) {
  return buffer.toString().split('\n').shift()
}

// publish for testing
exports.validateMessage = validateMessage

// lame test if run by git (so that it does not trigger during testing)
if (process.env.GIT_DIR) {
  var commitMsgFile = process.argv[2]
  var incorrectLogFile = path.dirname(commitMsgFile) + '/logs/incorrect-commit-msgs'

  fs.readFile(commitMsgFile, function (err, buffer) {
    var msg = firstLineFromBuffer(buffer)

    if (!validateMessage(msg)) {
      fs.appendFile(incorrectLogFile, msg + '\n', function () {
        process.exit(1)
      })
    } else {
      process.exit(0)
    }
  })
}