Adds Danger support

Summary:
Testing Danger support in CI. Continuation of #14964, which Circle stopped building.

Update your node modules first: `npm install`

`npm run danger pr https://github.com/facebook/react-native/pull/14951`
Verify output. This PR should trigger a WIP warning, as well as a package.json warning:

```
> react-native@1000.0.0 danger /Users/hramos/git/react-native
> node ./node_modules/.bin/danger "pr" "#14951"

{
  fails: [],
  warnings: [
    {
      message: ":construction_worker: Work In Progress - <i>Do not merge yet.</i>"
    },
    {
      message: ":lock: Changes were made to package.json - <i>This will require a manual import. Once approved, a Facebook employee should import the PR, then run `yarn add` for any new packages.</i>"
    }
  ],
  messages: [],
  markdowns: ["This PR requires attention from the facebook/react-native team."]
}
```

`npm run danger pr https://github.com/facebook/react-native/pull/14946`

Verify output. This PR should trigger a warning against the lack of a test plan (note that the PR does have a test plan, but it does not title it as such):
```
{
  fails: [],
  warnings: [
    {
      message: ":clipboard: Test Plan - <i>This PR appears to be missing a Test Plan</i>"
    }
  ],
  messages: [],
  markdowns: []
}
```

`npm run danger pr https://github.com/facebook/react-native/pull/13186`

Should warn against a missing test plan:

```
{
  fails: [],
  warnings: [
    {
      message: ":clipboard: Test Plan - <i>This PR appears to be missing a Test Plan.</i>"
    }
  ],
  messages: [],
  markdowns: [":page_facing_up: Thanks for your contribution to the docs!"]
}
```

If the author is able to issue bot commands, we reasonably assume that this is coming from an established core contributor. Their PRs will be flagged for expedited review:

`npm run danger pr https://github.com/facebook/react-native/pull/14895`

```
{
  fails: [],
  warnings: [
    {
      message: ":clipboard: Test Plan - <i>This PR appears to be missing a Test Plan.</i>"
    }
  ],
  messages: [],
  markdowns: ["This PR has been submitted by a core contributor. Notifying facebook/react-native."]
}
```
Closes #15061

Differential Revision: D5436605

Pulled By: hramos

fbshipit-source-id: 4ba9e812387d8a69893dab537af9b6cd108753cf

.flowconfig

@@ -8,6 +8,9 @@
 ; Ignore the website subdir
 <PROJECT_ROOT>/website/.*
 
+; Ignore the Dangerfile
+<PROJECT_ROOT>/danger/dangerfile.js
+
 ; Ignore "BUCK" generated dirs
 <PROJECT_ROOT>/\.buckd/
 

.gitignore

@@ -47,6 +47,7 @@ local.properties
 node_modules
 *.log
 .nvm
+/danger/node_modules/
 
 # OS X
 .DS_Store

circle.yml

@@ -34,12 +34,15 @@ dependencies:
     - npm install
     # for eslint bot
     - npm install github@0.2.4
+    # for website, danger
     - cd website && npm install
+    - cd danger && npm install
   cache_directories:
     - "ReactAndroid/build/downloads"
     - "/home/ubuntu/buck"
     - "website/node_modules"
     - "node_modules"
+    - "danger/node_modules"
 
 test:
   pre:
@@ -49,7 +52,9 @@ test:
     - source scripts/circle-ci-android-setup.sh && waitForAVD
 
   override:
-    # eslint bot. This GitHub token grants public_repo access scope.
+    # Run Danger against PRs. This GitHub token grants public_repo access scope. The associated account has no privileged access to the React Native repo. The token must be split in this manner to avoid revocation by GitHub.
+    - cd danger && DANGER_GITHUB_API_TOKEN="e622517d9f1136ea8900""07c6373666312cdfaa69" npm run danger
+    # eslint bot. This GitHub token grants public_repo access scope. The token must be split in this manner to avoid revocation by GitHub.
     - cat <(echo eslint; npm run lint --silent -- --format=json; echo flow; npm run flow --silent -- check --json) | GITHUB_TOKEN="af6ef0d15709bc91d""06a6217a5a826a226fb57b7" CI_USER=$CIRCLE_PROJECT_USERNAME CI_REPO=$CIRCLE_PROJECT_REPONAME PULL_REQUEST_NUMBER=$CIRCLE_PR_NUMBER node bots/code-analysis-bot.js
     - npm run lint
     # JS tests for dependencies installed with npm3

danger/.babelrc

@@ -0,0 +1 @@
+{}

danger/README.md

@@ -0,0 +1,12 @@
+If you'd like to make changes to the Dangerfile, find an existing PR and copy the URL.		
+
+Then run from the React Native root:		
+
+```
+cd danger
+npm install
+..
+node danger/node_modules/.bin/danger pr https://github.com/facebook/react-native/pull/1		
+```
+
+And you will get the responses from parsing the Dangerfile.

danger/dangerfile.js

@@ -0,0 +1,104 @@
+/**
+ * Copyright (c) 2013-present, 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.
+ */
+
+'use strict';
+
+const fs = require('fs');
+const includes = require('lodash.includes');
+
+import { danger, fail, markdown, warn } from 'danger';
+
+const isDocsFile = path => includes(path, 'docs/');
+const editsDocs = danger.git.modified_files.filter(isDocsFile).length > 0;
+const addsDocs = danger.git.created_files.filter(isDocsFile).length > 0;
+if (addsDocs || editsDocs) {
+  // Note, this does not yet cover edits to the autogenerated docs
+  // (e.g. comments within JS source files)
+  markdown(':page_facing_up: Thanks for your contribution to the docs!');
+}
+
+const isBlogFile = path => includes(path, 'blog/');
+
+// Flags new blog posts. Note that mentions will not be parsed as the access token we're using does
+// not belong to the Facebook org (on purpose)
+const addsBlogPost = danger.git.created_files.filter(isBlogFile).length > 0;
+if (addsBlogPost) {
+  const message = ':memo: Blog post';
+  const idea = 'This PR appears to add a new blog post, ' +
+    'and may require further review from the React Native team.';
+  warn(`${message} - <i>${idea}</i>`);
+  markdown(':memo: This PR requires attention from the @facebook/react-native team.');
+}
+
+// Flags edits to blog posts
+const editsBlogPost = danger.git.modified_files.filter(isBlogFile).length > 0;
+if (editsBlogPost) {
+  const message = ':memo: Blog post';
+  const idea = 'This PR appears to edit an existing blog post, ' +
+    'and may require further review from the React Native team.';
+  warn(`${message} - <i>${idea}</i>`);
+  markdown('This PR requires attention from the @facebook/react-native team.');
+}
+
+// Fails if the description is too short.
+if (danger.github.pr.body.length < 10) {
+  fail(':grey_question: This pull request needs a description.');
+}
+
+// Warns if the PR title contains [WIP]
+const isWIP = includes(danger.github.pr.title, '[WIP]');
+if (isWIP) {
+  const message = ':construction_worker: Work In Progress';
+  const idea = 'This PR appears to be a work in progress, and may not be ready to be merged yet.';
+  warn(`${message} - <i>${idea}</i>`);
+}
+
+// Warns if there are changes to package.json, and tags the team.
+const packageChanged = includes(danger.git.modified_files, 'package.json');
+if (packageChanged) {
+  const message = ':lock: package.json';
+  const idea = 'Changes were made to package.json. ' +
+    'This will require a manual import by a Facebook employee.';
+  warn(`${message} - <i>${idea}</i>`);
+  markdown('This PR requires attention from the @facebook/react-native team.');
+}
+
+// Warns if a test plan is missing.
+const gettingStartedChanged = includes(danger.git.modified_files, 'docs/GettingStarted.md');
+const includesTestPlan = danger.github.pr.body.toLowerCase().includes('test plan');
+
+// Warns if a test plan is missing, when editing the Getting Started guide. This page needs to be
+// tested in all its permutations.
+if (!includesTestPlan && gettingStartedChanged) {
+  const message = ':clipboard: Test Plan';
+  const idea = 'This PR appears to be missing a Test Plan.';
+  warn(`${message} - <i>${idea}</i>`);
+}
+// Doc edits rarely require a test plan. We'll trust the reviewer to push back if one is needed.
+if (!includesTestPlan && !editsDocs) {
+  const message = ':clipboard: Test Plan';
+  const idea = 'This PR appears to be missing a Test Plan.';
+  warn(`${message} - <i>${idea}</i>`);
+}
+
+// Tags PRs that have been submitted by a core contributor.
+const taskforce = fs.readFileSync('../bots/IssueCommands.txt', 'utf8').split('\n')[0].split(':')[1];
+const isSubmittedByTaskforce = includes(taskforce, danger.github.pr.user.login);
+if (isSubmittedByTaskforce) {
+  markdown('This PR has been submitted by a core contributor.');
+}
+
+// Warns if the bots whitelist file is updated.
+const isBotsCommandsFile = path => includes(path, 'bots/IssueCommands.txt');
+if (isBotsCommandsFile) {
+  const message = ':exclamation: Bots';
+  const idea = 'This PR appears to modify the list of people that may issue commands to the ' +
+    'GitHub bot.';
+  warn(`${message} - <i>${idea}</i>`);
+}

danger/package.json

@@ -0,0 +1,10 @@
+{
+  "private": true,
+  "scripts": {
+    "danger": "node ./node_modules/.bin/danger"
+  },
+  "devDependencies": {
+    "danger": "^0.21.2",
+    "lodash.includes": "^4.3.0"
+  }
+}