proposed fix for facebook#18223

Libraries/Network/XMLHttpRequest.js

@@ -1,3 +1,4 @@
+
 /**
  * Copyright (c) 2015-present, Facebook, Inc.
  *
@@ -181,7 +182,7 @@ class XMLHttpRequest extends EventTarget(...XHR_EVENTS) {
     if (this._sent) {
       throw new Error(
         "Failed to set the 'responseType' property on 'XMLHttpRequest': The " +
-          'response type cannot be set after the request has been sent.',
+        'response type cannot be set after the request has been sent.',
       );
     }
     if (!SUPPORTED_RESPONSE_TYPES.hasOwnProperty(responseType)) {
@@ -211,7 +212,7 @@ class XMLHttpRequest extends EventTarget(...XHR_EVENTS) {
     if (this._responseType !== '' && this._responseType !== 'text') {
       throw new Error(
         "The 'responseText' property is only available if 'responseType' " +
-          `is set to '' or 'text', but it is '${this._responseType}'.`,
+        `is set to '' or 'text', but it is '${this._responseType}'.`,
       );
     }
     if (this.readyState < LOADING) {
@@ -221,7 +222,7 @@ class XMLHttpRequest extends EventTarget(...XHR_EVENTS) {
   }
 
   get response(): Response {
-    const {responseType} = this;
+    const { responseType } = this;
     if (responseType === '' || responseType === 'text') {
       return this.readyState < LOADING || this._hasError ? '' : this._response;
     }
@@ -247,7 +248,11 @@ class XMLHttpRequest extends EventTarget(...XHR_EVENTS) {
         if (typeof this._response === 'object' && this._response) {
           this._cachedResponse = BlobManager.createFromOptions(this._response);
         } else {
-          throw new Error(`Invalid response for blob: ${this._response}`);
+          if (this._response === '') {
+            this._cachedResponse = null;
+          } else {
+            throw new Error(`Invalid response for blob: ${this._response}`);
+          }
         }
         break;
 
@@ -565,20 +570,20 @@ class XMLHttpRequest extends EventTarget(...XHR_EVENTS) {
 
   setReadyState(newState: number): void {
     this.readyState = newState;
-    this.dispatchEvent({type: 'readystatechange'});
+    this.dispatchEvent({ type: 'readystatechange' });
     if (newState === this.DONE) {
       if (this._aborted) {
-        this.dispatchEvent({type: 'abort'});
+        this.dispatchEvent({ type: 'abort' });
       } else if (this._hasError) {
         if (this._timedOut) {
-          this.dispatchEvent({type: 'timeout'});
+          this.dispatchEvent({ type: 'timeout' });
         } else {
-          this.dispatchEvent({type: 'error'});
+          this.dispatchEvent({ type: 'error' });
         }
       } else {
-        this.dispatchEvent({type: 'load'});
+        this.dispatchEvent({ type: 'load' });
       }
-      this.dispatchEvent({type: 'loadend'});
+      this.dispatchEvent({ type: 'loadend' });
     }
   }
 
@@ -595,4 +600,4 @@ class XMLHttpRequest extends EventTarget(...XHR_EVENTS) {
   }
 }
 
-module.exports = XMLHttpRequest;
+module.exports = XMLHttpRequest;