Moves from XHR to DevTools Protocol for manifest retrieval (#600)

* Moves from XHR to DevTools Protocol for manifest

Author: paullewis

lighthouse-core/gather/gatherers/manifest.js

@@ -19,40 +19,6 @@
 const Gatherer = require('./gatherer');
 const manifestParser = require('../../lib/manifest-parser');
 
-/* global document, XMLHttpRequest, __returnResults */
-
-/* istanbul ignore next */
-function getManifestContent() {
-  function post(response) {
-    // __returnResults is magically inserted by driver.evaluateAsync
-    __returnResults(response);
-  }
-
-  const manifestNode = document.querySelector('link[rel=manifest]');
-  if (!manifestNode) {
-    return post({error: 'No <link rel="manifest"> found in DOM.'});
-  }
-
-  const manifestURL = manifestNode.href;
-  if (!manifestURL) {
-    return post({error: 'No href found on <link rel="manifest">.'});
-  }
-
-  const req = new XMLHttpRequest();
-  req.open('GET', manifestURL);
-  req.onload = function() {
-    if (req.status !== 200) {
-      return post({
-        error: `Unable to fetch manifest at \
-          ${manifestURL}: ${req.status} - ${req.statusText}`
-      });
-    }
-
-    post({manifestContent: req.response});
-  };
-  req.send();
-}
-
 class Manifest extends Gatherer {
 
   static _errorManifest(errorString) {
@@ -70,23 +36,18 @@ class Manifest extends Gatherer {
      * potentially lead to a different asset. Using the original manifest
      * resource is tracked in issue #83
      */
-    return driver.evaluateAsync(`(${getManifestContent.toString()}())`)
-
-    .then(returnedValue => {
-      if (!returnedValue) {
+    return driver.sendCommand('Page.getAppManifest')
+      .then(response => {
+        if (response.errors.length) {
+          this.artifact = Manifest._errorManifest(response.errors.join(', '));
+          return;
+        }
+
+        this.artifact = manifestParser(response.data);
+      }, _ => {
         this.artifact = Manifest._errorManifest('Unable to retrieve manifest');
         return;
-      }
-
-      if (returnedValue.error) {
-        this.artifact = Manifest._errorManifest(returnedValue.error);
-      } else {
-        this.artifact = manifestParser(returnedValue.manifestContent);
-      }
-    }, _ => {
-      this.artifact = Manifest._errorManifest('Unable to retrieve manifest');
-      return;
-    });
+      });
   }
 }
 

lighthouse-core/test/gather/gatherers/manifest.js

@@ -34,8 +34,8 @@ describe('Manifest gatherer', () => {
   it('returns an artifact', () => {
     return manifestGather.afterPass({
       driver: {
-        evaluateAsync() {
-          return Promise.resolve('');
+        sendCommand() {
+          return Promise.resolve({data: '', errors: [], url: 'https://example.com/manifest.json'});
         }
       }
     }).then(_ => {
@@ -46,7 +46,7 @@ describe('Manifest gatherer', () => {
   it('handles driver failure', () => {
     return manifestGather.afterPass({
       driver: {
-        evaluateAsync() {
+        sendCommand() {
           return Promise.reject('such a fail');
         }
       }
@@ -61,9 +61,9 @@ describe('Manifest gatherer', () => {
     const error = 'There was an error.';
     return manifestGather.afterPass({
       driver: {
-        evaluateAsync() {
+        sendCommand() {
           return Promise.resolve({
-            error
+            errors: [error]
           });
         }
       }
@@ -73,14 +73,15 @@ describe('Manifest gatherer', () => {
   });
 
   it('creates a manifest object for valid manifest content', () => {
-    const manifestContent = JSON.stringify({
+    const data = JSON.stringify({
       name: 'App'
     });
     return manifestGather.afterPass({
       driver: {
-        evaluateAsync() {
+        sendCommand() {
           return Promise.resolve({
-            manifestContent
+            errors: [],
+            data
           });
         }
       }