Merge pull request #325 from jakubrohleder/fix/prefixing-data-urls

PrefixLink fixes

Author: KyleAMathews

lib/isomorphic/gatsby-helpers.js

@@ -3,6 +3,13 @@ import { config } from 'config'
 import invariant from 'invariant'
 import _ from 'lodash'
 
+function isDataURL (s) {
+  // Regex from https://gist.github.com/bgrins/6194623#gistcomment-1671744
+  // eslint-disable-next-line max-len
+  const regex = /^\s*data:([a-z]+\/[a-z0-9\-\+]+(;[a-z\-]+=[a-z0-9\-]+)?)?(;base64)?,[a-z0-9!\$&',\(\)\*\+,;=\-\._~:@\/\?%\s]*\s*$/i
+  return !!s.match(regex)
+}
+
 // Function to add prefix to links.
 const prefixLink = (_link) => {
   if (
@@ -15,7 +22,11 @@ const prefixLink = (_link) => {
     `
     invariant(_.isString(config.linkPrefix), invariantMessage)
 
-    return config.linkPrefix + _link
+    if (isDataURL(_link)) {
+      return _link
+    } else {
+      return config.linkPrefix + _link
+    }
   } else {
     return _link
   }