Initial commit

.gitignore

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+node_modules

Dockerfile

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+FROM node:10.15.1-alpine
+
+WORKDIR /app
+COPY . .
+
+RUN yarn
+
+CMD /usr/local/bin/node /app/plugin.js

README.md

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+# Drone Config Plugin - Changeset Conditional
+
+This implements the ability to have steps / pipelines only execute when certain files have changed, using the following additional YAML syntax:
+
+```
+pipeline:
+  frontend:
+    image: node
+    commands:
+      - cd app
+      - npm run test
++   when:
++     changeset:
++       includes: [ **/**.js, **/**.css, **/**.html ]
+  backend:
+    image: golang
+    commands:
+      - go build
+      - go test -v
++   when:
++     changeset:
++       includes: [ **/**.go ]
+
++changeset:
++  includes: [ **/**.go ]
+```
+
+## Installation
+
+PLEASE NOTE: At the moment it supports only github.com installations.
+
+Generate a GitHub access token with repo permission. This token is used to fetch the `.drone.yml` file and details of the files changed.
+
+Generate a shared secret key. This key is used to secure communication between the server and agents. The secret should be 32 bytes.
+```
+$ openssl rand -hex 16
+558f3eacbfd5928157cbfe34823ab921
+```
+
+Run the container somewhere where the drone server can reach it:
+
+```
+docker run \
+  -p ${PLUGIN_PORT}:3000 \
+  -e PLUGIN_SECRET=558f3eacbfd5928157cbfe34823ab921 \
+  -e GITHUB_TOKEN=GITHUB8168c98304b \
+  --name drone-changeset-conditional \
+  microadam/drone-config-plugin-changeset-conditional
+```
+
+Update your drone server with information about the plugin:
+
+```
+-e DRONE_YAML_ENDPOINT=http://${PLUGIN_HOST}:${PLUGIN_PORT}
+-e DRONE_YAML_SECRET=558f3eacbfd5928157cbfe34823ab921
+```
+
+See [the official docs](https://docs.drone.io/extend/config) for extra information on installing a Configuration Provider Plugin.
+
+## Pattern Matching
+
+This uses the [Glob](https://www.npmjs.com/package/glob) module under the hood, so supports all pattern matching syntaxes of this module.

lib/files-changed-determiner.js

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+const { promisify } = require('util')
+const getCommit = gh => async data => {
+  let commitData = null
+  const options = {
+    user: data.repo.namespace,
+    repo: data.repo.name,
+    base: data.build.before,
+    head: data.build.after
+  }
+  const comparison = await promisify(gh.repos.compareCommits)(options)
+  return comparison.files.map(f => f.filename)
+}
+
+module.exports = getCommit

lib/parsed-yaml-retriever.js

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+const { promisify } = require('util')
+const yaml = require('yamljs')
+const getParsedYaml = gh => async data => {
+  let file = null
+  const options = {
+    user: data.repo.namespace,
+    repo: data.repo.name,
+    ref: data.build.ref,
+    path: data.repo.config_path
+  }
+  file = await promisify(gh.repos.getContent)(options)
+  const contents = Buffer.from(file.content, 'base64').toString()
+  const parsed = yaml.parse(contents)
+  return parsed
+}
+
+module.exports = getParsedYaml

lib/signature-validator.js

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+const httpSignature = require('http-signature')
+const isValidSig = (req, hmac) => {
+  req.headers.signature = 'Signature ' + req.headers.signature
+  const parsedSig = httpSignature.parseRequest(req, { authorizationHeaderName: 'signature' })
+  return httpSignature.verifyHMAC(parsedSig, hmac)
+}
+
+module.exports = isValidSig

package.json

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+{
+  "name": "drone-config-changeset-conditional",
+  "version": "1.0.0",
+  "description": "",
+  "main": "plugin.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "",
+  "license": "ISC",
+  "dependencies": {
+    "body-parser": "^1.18.3",
+    "express": "^4.16.4",
+    "github4": "^1.1.1",
+    "globule": "^1.2.1",
+    "http-signature": "^1.2.0",
+    "yamljs": "^0.3.0"
+  }
+}

plugin.js

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+const express = require('express')
+const bodyParser = require('body-parser')
+const GhApi = require('github4')
+const yaml = require('yamljs')
+const glob = require('globule')
+const createFilesChangedDeterminer = require('./lib/files-changed-determiner')
+const createParsedYamlRetriever = require('./lib/parsed-yaml-retriever')
+const isValidSig = require('./lib/signature-validator')
+
+const githubToken = process.env.GITHUB_TOKEN
+const sharedKey = process.env.PLUGIN_SECRET
+
+const gh = new GhApi({ version: '3.0.0' })
+gh.authenticate({ type: 'oauth', token: githubToken })
+
+const determineFilesChanged = createFilesChangedDeterminer(gh)
+const getParsedYaml = createParsedYamlRetriever(gh)
+
+const nullYaml = 'kind: pipeline\nname: default\ntrigger:\n  event:\n    exclude: [ "*" ]'
+
+const app = express()
+app.post('/', bodyParser.json(), async (req, res) => {
+  console.log('Processing...')
+  if (!req.headers.signature) return res.status(400).send('Missing signature')
+  if (!isValidSig(req, sharedKey)) return res.status(400).send('Invalid signature')
+  if (!req.body) return res.sendStatus(400)
+  const data = req.body
+
+  let filesChanged = []
+  try {
+    filesChanged = await determineFilesChanged(data)
+  } catch (e) {
+    console.log('ERROR:', e)
+    return res.sendStatus(500)
+  }
+
+  console.log('Files changed:', filesChanged)
+
+  let parsedYaml = null
+  try {
+    parsedYaml = await getParsedYaml(data)
+  } catch (e) {
+    if (e.code === 404) return res.sendStatus(204)
+    console.log('ERROR:', e)
+    return res.sendStatus(500)
+  }
+
+  if (parsedYaml.trigger && parsedYaml.trigger.changeset && parsedYaml.trigger.changeset.includes) {
+    const requiredFiles = parsedYaml.trigger.changeset.includes
+    const matchedFiles = glob.match(requiredFiles, filesChanged, { dot: true })
+    console.log('Matched files for pipeline:', matchedFiles.length, 'Allowed matches:', requiredFiles)
+    if (!matchedFiles.length) return res.json({ Data: nullYaml })
+  }
+
+  const trimmedSteps = parsedYaml.steps.filter(s => {
+    if (!s.when || !s.when.changeset || !s.when.changeset.includes) return true
+    const requiredFiles = s.when.changeset.includes
+    const matchedFiles = glob.match(requiredFiles, filesChanged, { dot: true })
+    console.log('Matched files for step:', matchedFiles.length, 'Allowed matches:', requiredFiles)
+    return matchedFiles.length
+  })
+
+  const returnYaml = trimmedSteps.length ? yaml.stringify({ ...parsedYaml, steps: trimmedSteps }) : nullYaml
+
+  res.json({ Data: returnYaml })
+})
+
+app.listen(3000)