Fix - File fetching broken since commit 0c1d2b9 (#1375)

fetch.js

@@ -538,10 +538,16 @@ export function fetch(input, init) {
 
     xhr.onload = function() {
       var options = {
-        status: xhr.status,
         statusText: xhr.statusText,
         headers: parseHeaders(xhr.getAllResponseHeaders() || '')
       }
+      // This check if specifically for when a user fetches a file locally from the file system
+      // Only if the status is out of a normal range
+      if (request.url.startsWith('file://') && (xhr.status < 200 || xhr.status > 599)) {
+        options.status = 200;
+      } else {
+        options.status = xhr.status;
+      }
       options.url = 'responseURL' in xhr ? xhr.responseURL : options.headers.get('X-Request-URL')
       var body = 'response' in xhr ? xhr.response : xhr.responseText
       setTimeout(function() {
@@ -632,4 +638,4 @@ if (!g.fetch) {
   g.Headers = Headers
   g.Request = Request
   g.Response = Response
-}
+}

test/test.js

@@ -647,7 +647,15 @@ exercise.forEach(function(exerciseMode) {
             new Response('', {status: i})
           })
         }
+        // A fetch with the url of a `file://` scheme may have a status 0 or
+        // similar in some operating systems. In the event that a status is found outside 
+        // the standard range of 200-599, and the url start with `file://`
+        // the status should return 200
+        assert.doesNotThrow(function() {
+          new Request('', {status: 0, request: {url: 'file://path/to/local/file'}})
+        })
       })
+
       test('creates Headers object from raw headers', function() {
         var r = new Response('{"foo":"bar"}', {headers: {'content-type': 'application/json'}})
         assert.equal(r.headers instanceof Headers, true)