dangerfile.js

const { danger, fail, warn } = require('danger')
const _ = require('lodash/fp')

const log = (f, s) => console.log(f.name, s) & f(s)

const changed = {
  changelog: _.includes('CHANGELOG.md', danger.git.modified_files),
  packageJSON: _.includes('package.json', danger.git.modified_files)
}

// No PR is too small to warrant a paragraph or two of summary
if (danger.github.pr.body.length === 0) {
  log(fail, 'Please add a description to your PR.')
}

// Always ensure we assign someone, so that our Slackbot can do its work correctly
if (danger.github.pr.assignee === null) {
  log(fail, 'Please assign someone to merge this PR, and optionally include people who should review.')
}

// Requires CHANGELOG entries
if (!changed.changelog) {
  log(fail, 'Please add a changelog entry for your changes.')
}

// Requires a version update in package.json
const packageDiff = danger.git.diffForFile('package.json')
if (!changed.packageJSON && packageDiff && packageDiff.includes('version')) {
  log(fail, 'Please bump up the version')
}

// Warns when PR size is large
const bigPRThreshold = 600
if (danger.github.pr.additions + danger.github.pr.deletions > bigPRThreshold) {
  log(warn, `:exclamation: This PR is BIG (+${danger.github.pr.additions} -${danger.github.pr.deletions})`)
}