Adds support for using Danger on PRs (jestjs#2508)

* Initial Dangerfile, adds a rule for including flow and the FB header

* [Danger] Use a local path for jest-runtime instead of the downloaded NPM package

* [Danger] Makes the FB copyright header check correct

* just run danger

* Update Danger

.flowconfig

@@ -5,6 +5,7 @@
 .*/vendor/jsonlint/.*
 .*/examples/.*
 .*/website/.*
+.*/dangerfile.js
 
 [options]
 module.name_mapper='^types/\(.*\)$' -> '<PROJECT_ROOT>/types/\1.js'

dangerfile.js

@@ -0,0 +1,75 @@
+// @flow
+
+const {danger, fail, warn} = require('danger');
+const fs = require('fs');
+
+// Takes a list of file paths, and converts it into clickable links
+const linkableFiles = (paths: Array<string>): string => {
+  const repoURL = danger.github.pr.head.repo.html_url;
+  const ref = danger.github.pr.head.ref;
+  const links = paths.map(path => {
+    return createLink(`${repoURL}/blob/${ref}/${path}`, path);
+  });
+  return toSentence(links);
+};
+
+// ["1", "2", "3"] to "1, 2 and 3"
+const toSentence = (array: Array<string>) : string => {
+  if (array.length === 1) { return array[0]; }
+  return array.slice(0, array.length - 1).join(', ') + ' and ' + array.pop();
+};
+
+// ("/href/thing", "name") to "<a href="/href/thing">name</a>"
+const createLink = (href: string, text: string): string => 
+  `<a href='${href}'>${text}</a>`;
+
+const newJsFiles = danger.git.created_files.filter(path => path.endsWith('js'));
+
+// New JS files should have the FB copyright header + flow
+const facebookLicenseHeaderComponents = [
+  'Copyright \(c\) .*, Facebook, Inc. All rights reserved.',
+  'This source code is licensed under the BSD-style license found in the',
+  'LICENSE file in the root directory of this source tree. An additional grant',
+  'of patent rights can be found in the PATENTS file in the same directory.',
+];
+
+const noFBCopyrightFiles = newJsFiles.filter(filepath => {
+  const content = fs.readFileSync(filepath).toString();
+  for (const line of facebookLicenseHeaderComponents) {
+    if (!content.match(new RegExp(line))) {
+      return true;
+    }
+  }
+  return false;
+});
+
+if (noFBCopyrightFiles.length > 0) {
+  const files = linkableFiles(noFBCopyrightFiles);
+  fail(`New JS files do not have the Facebook copyright header: ${files}`);
+}
+
+// Ensure the use of Flow and 'use strict';
+const noFlowFiles = newJsFiles.filter(filepath => {
+  const content = fs.readFileSync(filepath).toString();
+  return content.includes('@flow') && content.includes('use strict');
+});
+
+if (noFlowFiles.length > 0) {
+  const files = linkableFiles(noFlowFiles);
+  const flow = '<code>@flow</code>';
+  const strict = "<code>'use strict'</code>";
+  warn(`Please ensure that ${flow} and ${strict} are enabled on: ${files}`);
+}
+
+// No merge from master commmits
+// TODO: blocked by https://github.com/danger/danger-js/issues/81
+
+// Warns if there are changes to package.json without changes to yarn.lock.
+
+const packageChanged = danger.git.modified_files.includes('package.json');
+const lockfileChanged = danger.git.modified_files.includes('yarn.lock');
+if (packageChanged && !lockfileChanged) {
+  const message = 'Changes were made to package.json, but not to yarn.lock';
+  const idea = 'Perhaps you need to run `yarn install`?';
+  warn(`${message} - <i>${idea}</i>`);
+}

package.json

@@ -10,6 +10,7 @@
     "babel-plugin-transform-flow-strip-types": "^6.18.0",
     "chalk": "^1.1.3",
     "codecov": "^1.0.1",
+    "danger": "^0.8.0",
     "eslint": "^3.11.1",
     "eslint-plugin-babel": "^4.0.0",
     "eslint-plugin-flow-vars": "^0.5.0",
@@ -21,6 +22,7 @@
     "istanbul-api": "^1.1.0",
     "istanbul-lib-coverage": "^1.0.0",
     "jasmine-reporters": "^2.2.0",
+    "jest-runtime": "file:./packages/jest-runtime/",
     "jsdom": "^9.9.1",
     "left-pad": "^1.1.1",
     "lerna": "2.0.0-beta.32",
@@ -43,7 +45,7 @@
     "postinstall": "node ./scripts/postinstall.js && node ./scripts/build.js",
     "publish": "yarn run build-clean && yarn run build && lerna publish",
     "test": "yarn run typecheck && yarn run lint && yarn run build && yarn run jest && yarn run test-examples",
-    "test-ci": "yarn run typecheck && yarn run lint && yarn run build && yarn run jest-coverage -- -i && yarn run test-examples && node scripts/mapCoverage.js && codecov",
+    "test-ci": "yarn run typecheck && yarn run lint && yarn run build && yarn run jest-coverage -- -i && yarn run test-examples && node scripts/mapCoverage.js && codecov && yarn run danger",
     "test-examples": "node scripts/test_examples.js",
     "typecheck": "flow check",
     "watch": "yarn run build; node ./scripts/watch.js"