feat(graphql): serve a favicon from GraphQL HTTP

src/graphql/http/__tests__/createGraphqlHTTPRequestHandler-test.js

@@ -336,5 +336,24 @@ for (const [name, createServer] of serverCreators) {
         .expect({ data: { greetings: 'Hello, Joe!' } })
       )
     })
+
+    test('will serve a favicon', async () => {
+      const server1 = createServer()
+      const server2 = createServer({ route: '/graphql' })
+      await (
+        request(server1)
+        .get('/favicon.ico')
+        .expect(200)
+        .expect('Cache-Control', 'public, max-age=86400')
+        .expect('Content-Type', 'image/x-icon')
+      )
+      await (
+        request(server2)
+        .get('/favicon.ico')
+        .expect(200)
+        .expect('Cache-Control', 'public, max-age=86400')
+        .expect('Content-Type', 'image/x-icon')
+      )
+    })
   })
 }

src/graphql/http/createGraphqlHTTPRequestHandler.js

@@ -1,4 +1,5 @@
 import { resolve as resolvePath } from 'path'
+import { readFile } from 'fs'
 import { parse as parseQueryString } from 'querystring'
 import { IncomingMessage, ServerResponse } from 'http'
 const httpError = require('http-errors')
@@ -16,6 +17,13 @@ import {
 import { Inventory } from '../../interface'
 import createGraphqlSchema from '../schema/createGraphqlSchema'
 
+const favicon = new Promise((resolve, reject) => {
+  readFile(resolvePath(__dirname, '../../../resources/favicon.ico'), (error, data) => {
+    if (error) reject(error)
+    else resolve(data)
+  })
+})
+
 // TODO: test `express`
 // TODO: test `connect`
 // TODO: test `koa`
@@ -53,6 +61,26 @@ export default function createGraphqlHTTPRequestHandler (inventory, options = {}
    * @param {ServerResponse} res
    */
   const requestHandler = async (req, res, next) => {
+    // If this is the favicon path and it has not yet been handled, let us
+    // serve our GraphQL favicon.
+    if (parseUrl(req).pathname === '/favicon.ico') {
+      // If this is the wrong method, we should let the client know.
+      if (!(req.method === 'GET' || req.method === 'HEAD')) {
+        res.statusCode = req.method === 'OPTIONS' ? 200 : 405
+        res.setHeader('Allow', 'GET, HEAD, OPTIONS')
+        res.end()
+        return
+      }
+
+      // Otherwise we are good and should pipe the favicon to the browser.
+      res.statusCode = 200
+      res.setHeader('Cache-Control', 'public, max-age=86400')
+      res.setHeader('Content-Type', 'image/x-icon')
+      res.end(await favicon)
+
+      return
+    }
+
     // Don’t handle any requests if this is not the correct route.
     if (parseUrl(req).pathname !== (options.route || '/'))
       return next()