improvement: factor out Accept value for document fetches (#1478)

* improve: factor out Accept value for document fetches

* fix import path

Author: shockey

src/constants.js

@@ -0,0 +1 @@
+export const ACCEPT_HEADER_VALUE_FOR_DOCUMENTS = 'application/json, application/yaml'

src/resolver.js

@@ -1,6 +1,7 @@
 import Http from './http'
 import mapSpec, {plugins} from './specmap'
 import {normalizeSwagger} from './helpers'
+import {ACCEPT_HEADER_VALUE_FOR_DOCUMENTS} from './constants'
 
 export function makeFetchJSON(http, opts = {}) {
   const {requestInterceptor, responseInterceptor} = opts
@@ -13,7 +14,7 @@ export function makeFetchJSON(http, opts = {}) {
       requestInterceptor,
       responseInterceptor,
       headers: {
-        Accept: 'application/json'
+        Accept: ACCEPT_HEADER_VALUE_FOR_DOCUMENTS
       },
       credentials
     })

src/specmap/lib/refs.js

@@ -5,6 +5,7 @@ import url from 'url'
 import lib from '../lib'
 import createError from '../lib/create-error'
 import {isFreelyNamed, absolutifyPointer} from '../helpers'
+import {ACCEPT_HEADER_VALUE_FOR_DOCUMENTS} from '../../constants'
 
 const ABSOLUTE_URL_REGEXP = new RegExp('^([a-z]+://|//)', 'i')
 
@@ -315,7 +316,7 @@ function getDoc(docPath) {
  * @api public
  */
 function fetchJSON(docPath) {
-  return fetch(docPath, {headers: {Accept: 'application/json, application/yaml'}, loadSpec: true})
+  return fetch(docPath, {headers: {Accept: ACCEPT_HEADER_VALUE_FOR_DOCUMENTS}, loadSpec: true})
     .then(res => res.text())
     .then(text => jsYaml.safeLoad(text))
 }