feat: ping reviewers based on which files were changed

Using a custom OWNERS file, `github-bot` will ping the appropriate teams
based on which files were changed in a Pull Request. This feature is
inteded to work around GitHub's limitation which prevents teams without
explicit write access from being added as reviewers (thus preventing the
vast majority of teams in the org from being used on GitHub's CODEOWNERS
feature).

The OWNERS file is a yaml file (to simplify parsing) composed of
key-value paris. The key is always a string and represents a glob of the
changed files. The value is always an array of strings, and each string
is a team to be pinged.

Ref: nodejs/node#33984

lib/node-owners.js

@@ -0,0 +1,32 @@
+'use static'
+
+const yaml = require('js-yaml')
+const micromatch = require('micromatch')
+
+class Owners {
+  constructor (ownersDefinitions) {
+    console.log(ownersDefinitions)
+    this._ownersDefinitions = ownersDefinitions
+  }
+
+  static fromYaml (content) {
+    console.log(content)
+    return new Owners(yaml.safeLoad(content))
+  }
+
+  getOwnersForPaths (paths) {
+    let owners = []
+    for (const ownersGlob of Object.keys(this._ownersDefinitions)) {
+      console.log(paths, ownersGlob, micromatch(paths, ownersGlob))
+      if (micromatch(paths, ownersGlob).length > 0) {
+        owners = owners.concat(this._ownersDefinitions[ownersGlob])
+      }
+    }
+    // Remove duplicates before returning
+    return owners.filter((v, i) => owners.indexOf(v) === i)
+  }
+}
+
+module.exports = {
+  Owners
+}

lib/node-repo.js

@@ -1,42 +1,88 @@
 'use strict'
 
+const request = require('request')
 const LRU = require('lru-cache')
 const retry = require('async').retry
+const debug = require('debug')('node_repo')
 
 const githubClient = require('./github-client')
 const resolveLabels = require('./node-labels').resolveLabels
+const { Owners } = require('./node-owners')
+const { createPrComment } = require('./github-comment')
 const existingLabelsCache = new LRU({ max: 1, maxAge: 1000 * 60 * 60 })
 
 const fiveSeconds = 5 * 1000
 
-function deferredResolveLabelsThenUpdatePr (options) {
-  const timeoutMillis = (options.timeoutInSec || 0) * 1000
-  setTimeout(resolveLabelsThenUpdatePr, timeoutMillis, options)
-}
-
-function resolveLabelsThenUpdatePr (options) {
+function getFilepathsChanged (options, handleFilepaths) {
   options.logger.debug('Fetching PR files for labelling')
 
-  const getFiles = (cb) => {
+  const getPRFiles = (cb) => {
     githubClient.pullRequests.getFiles({
       owner: options.owner,
       repo: options.repo,
       number: options.prId
     }, cb)
   }
 
-  retry({ times: 5, interval: fiveSeconds }, getFiles, (err, res) => {
+  retry({ times: 5, interval: fiveSeconds }, getPRFiles, (err, res) => {
     if (err) {
       return options.logger.error(err, 'Error retrieving files from GitHub')
     }
-
     const filepathsChanged = res.data.map((fileMeta) => fileMeta.filename)
-    const resolvedLabels = resolveLabels(filepathsChanged, options.baseBranch)
 
-    fetchExistingThenUpdatePr(options, resolvedLabels)
+    handleFilepaths(options, filepathsChanged)
   })
 }
 
+function deferredResolveOwnersThenPingPr (options) {
+  const timeoutMillis = (options.timeoutInSec || 0) * 1000
+  setTimeout(() => getFilepathsChanged(options, resolveOwnersThenPingPr), timeoutMillis, options)
+}
+
+function resolveOwnersThenPingPr (options, filepathsChanged) {
+  const { owner, repo } = options
+  githubClient.repos.get({
+    owner,
+    repo
+  }, (err, res) => {
+    if (err) {
+      return options.logger.error(err, 'Error retrieving repository data')
+    }
+    const data = res.data || {}
+    if (!data['default_branch']) {
+      return options.logger.error(err, 'Couldn\' determine default branch')
+    }
+
+    const { default_branch: defaultBranch } = data
+
+    const url = `https://raw.githubusercontent.com/${owner}/${repo}/${defaultBranch}/OWNERS.yml`
+    debug(`Fetching OWNERS on ${url}`)
+    request(url, (err, res, body) => {
+      if (err || !res || res.statusCode >= 400) {
+        return options.logger.error(err, 'Error retrieving OWNERS')
+      }
+      const owners = Owners.fromYaml(body)
+      const selectedOwners = owners.getOwnersForPaths(filepathsChanged)
+      console.log(selectedOwners)
+      if (selectedOwners.length > 0) {
+        pingOwners(options, selectedOwners)
+      }
+      console.log('done')
+    })
+  })
+}
+
+function deferredResolveLabelsThenUpdatePr (options) {
+  const timeoutMillis = (options.timeoutInSec || 0) * 1000
+  setTimeout(() => getFilepathsChanged(options, resolveLabelsThenUpdatePr), timeoutMillis, options)
+}
+
+function resolveLabelsThenUpdatePr (options, filepathsChanged) {
+  const resolvedLabels = resolveLabels(filepathsChanged, options.baseBranch)
+
+  fetchExistingThenUpdatePr(options, resolvedLabels)
+}
+
 function fetchExistingThenUpdatePr (options, labels) {
   fetchExistingLabels(options, (err, existingLabels) => {
     if (err) {
@@ -53,6 +99,21 @@ function fetchExistingThenUpdatePr (options, labels) {
   })
 }
 
+function pingOwners (options, owners) {
+  createPrComment({
+    owner: options.owner,
+    repo: options.repo,
+    number: options.prId,
+    logger: options.logger
+  }, `Review requested:\n\n${owners.map(i => `- [ ] ${i}`).join('\n')}`, (err) => {
+    if (err) {
+      return options.logger.error(err, 'Error while pinging owners')
+    }
+
+    options.logger.info('Pinged owners: ' + owners)
+  })
+}
+
 function updatePrWithLabels (options, labels) {
   // no need to request github if we didn't resolve any labels
   if (!labels.length) {
@@ -192,6 +253,7 @@ exports.getBotPrLabels = getBotPrLabels
 exports.removeLabelFromPR = removeLabelFromPR
 exports.fetchExistingThenUpdatePr = fetchExistingThenUpdatePr
 exports.resolveLabelsThenUpdatePr = deferredResolveLabelsThenUpdatePr
+exports.resolveOwnersThenPingPr = deferredResolveOwnersThenPingPr
 
 // exposed for testability
 exports._fetchExistingLabels = fetchExistingLabels