Adding waitForTimeout/waitForSelector for assets discovery browser wh…

…en JS is enabled (#1715)

packages/core/src/config.js

@@ -196,6 +196,14 @@ export const configSchema = {
         maximum: 750,
         minimum: 1
       },
+      waitForSelector: {
+        type: 'string'
+      },
+      waitForTimeout: {
+        type: 'integer',
+        minimum: 1,
+        maximum: 30000
+      },
       disableCache: {
         type: 'boolean'
       },
@@ -295,6 +303,8 @@ export const snapshotSchema = {
             allowedHostnames: { $ref: '/config/discovery#/properties/allowedHostnames' },
             disallowedHostnames: { $ref: '/config/discovery#/properties/disallowedHostnames' },
             requestHeaders: { $ref: '/config/discovery#/properties/requestHeaders' },
+            waitForSelector: { $ref: '/config/discovery#/properties/waitForSelector' },
+            waitForTimeout: { $ref: '/config/discovery#/properties/waitForTimeout' },
             authorization: { $ref: '/config/discovery#/properties/authorization' },
             disableCache: { $ref: '/config/discovery#/properties/disableCache' },
             captureMockedServiceWorker: { $ref: '/config/discovery#/properties/captureMockedServiceWorker' },

packages/core/src/discovery.js

@@ -1,5 +1,6 @@
 import logger from '@percy/logger';
 import Queue from './queue.js';
+import Page from './page.js';
 import {
   normalizeURL,
   hostnameMatches,
@@ -9,7 +10,9 @@ import {
   createLogResource,
   yieldAll,
   snapshotLogName,
-  withRetries
+  waitForTimeout,
+  withRetries,
+  waitForSelectorInsideBrowser
 } from './utils.js';
 import {
   sha256hash
@@ -203,6 +206,18 @@ async function* captureSnapshotResources(page, snapshot, options) {
   yield resizePage(snapshot.widths[0]);
   yield page.goto(snapshot.url, { cookies });
 
+  // wait for any specified timeout
+  if (snapshot.discovery.waitForTimeout && page.enableJavaScript) {
+    log.debug(`Wait for ${snapshot.discovery.waitForTimeout}ms timeout`);
+    await waitForTimeout(snapshot.discovery.waitForTimeout);
+  }
+
+  // wait for any specified selector
+  if (snapshot.discovery.waitForSelector && page.enableJavaScript) {
+    log.debug(`Wait for selector: ${snapshot.discovery.waitForSelector}`);
+    await waitForSelectorInsideBrowser(page, snapshot.discovery.waitForSelector, Page.TIMEOUT);
+  }
+
   if (snapshot.execute) {
     // when any execute options are provided, inject snapshot options
     /* istanbul ignore next: cannot detect coverage of injected code */

packages/core/src/snapshot.js

@@ -130,6 +130,8 @@ function getSnapshotOptions(options, { config, meta }) {
       allowedHostnames: config.discovery.allowedHostnames,
       disallowedHostnames: config.discovery.disallowedHostnames,
       networkIdleTimeout: config.discovery.networkIdleTimeout,
+      waitForTimeout: config.discovery.waitForTimeout,
+      waitForSelector: config.discovery.waitForSelector,
       devicePixelRatio: config.discovery.devicePixelRatio,
       requestHeaders: config.discovery.requestHeaders,
       authorization: config.discovery.authorization,

packages/core/src/utils.js

@@ -257,6 +257,15 @@ async function waitForSelector(selector, timeout) {
   }
 }
 
+// wait for a query selector to exist within an optional timeout inside browser
+export async function waitForSelectorInsideBrowser(page, selector, timeout) {
+  try {
+    return page.eval(`await waitForSelector(${JSON.stringify(selector)}, ${timeout})`);
+  } catch {
+    throw new Error(`Unable to find: ${selector}`);
+  }
+}
+
 // Browser-specific util to wait for an xpath selector to exist within an optional timeout.
 /* istanbul ignore next: tested, but coverage is stripped */
 async function waitForXPath(selector, timeout) {

packages/core/test/discovery.test.js

@@ -2430,6 +2430,77 @@ describe('Discovery', () => {
     });
   });
 
+  describe('waitForSelector/waitForTimeout at the time of discovery when Js is enabled =>', () => {
+    it('calls waitForTimeout, waitForSelector and page.eval when their respective arguments are given', async () => {
+      const page = await percy.browser.page();
+      spyOn(percy.browser, 'page').and.returnValue(page);
+      spyOn(page, 'eval').and.callThrough();
+      percy.loglevel('debug');
+
+      await percy.snapshot({
+        name: 'test discovery',
+        url: 'http://localhost:8000',
+        enableJavaScript: true,
+        discovery: {
+          waitForTimeout: 100,
+          waitForSelector: 'body'
+        }
+      });
+      await percy.idle();
+
+      expect(page.eval).toHaveBeenCalledWith('await waitForSelector("body", 30000)');
+      expect(logger.stderr).toEqual(jasmine.arrayContaining([
+        '[percy:core:discovery] Wait for selector: body',
+        '[percy:core:discovery] Wait for 100ms timeout'
+      ]));
+    });
+  });
+  describe('waitForSelector/waitForTimeout at the time of discovery when Js is disabled =>', () => {
+    it('donot calls waitForTimeout, waitForSelector and page.eval', async () => {
+      const page2 = await percy.browser.page();
+      spyOn(page2, 'eval').and.callThrough();
+      percy.loglevel('debug');
+
+      await percy.snapshot({
+        name: 'test discovery 2',
+        url: 'http://localhost:8000',
+        cliEnableJavaScript: false,
+        discovery: {
+          waitForTimeout: 100,
+          waitForSelector: 'flex'
+        }
+      });
+
+      await percy.idle();
+
+      expect(page2.eval).not.toHaveBeenCalledWith('await waitForSelector("flex", 30000)');
+      expect(logger.stderr).not.toEqual(jasmine.arrayContaining([
+        '[percy:core:discovery] Wait for 100ms timeout',
+        '[percy:core:discovery] Wait for selector: flex'
+      ]));
+    });
+    it('when domSnapshot is present with default parameters waitForSelector/waitForTimeout are not called', async () => {
+      percy.loglevel('debug');
+
+      await percy.snapshot({
+        name: 'test discovery 3',
+        url: 'http://localhost:8000',
+        domSnapshot: testDOM,
+        discovery: {
+          waitForTimeout: 100,
+          waitForSelector: 'body'
+        }
+      });
+
+      await percy.idle();
+
+      expect(logger.stderr).not.toEqual(jasmine.arrayContaining([
+        '[percy:core:discovery] Wait for 100ms timeout',
+        '[percy:core:discovery] Wait for selector: body'
+      ]));
+    });
+  });
+
   describe('Capture image srcset =>', () => {
     it('make request call to capture resource', async () => {
       let responsiveDOM = dedent`

packages/core/test/utils.test.js

@@ -1,6 +1,7 @@
-import { decodeAndEncodeURLWithLogging } from '../src/utils.js';
-import { logger } from './helpers/index.js';
+import { decodeAndEncodeURLWithLogging, waitForSelectorInsideBrowser } from '../src/utils.js';
+import { logger, setupTest } from './helpers/index.js';
 import percyLogger from '@percy/logger';
+import Percy from '@percy/core';
 
 describe('utils', () => {
   let log;
@@ -45,4 +46,31 @@ describe('utils', () => {
       expect(logger.stderr).toEqual(['[percy] some Warning Message']);
     });
   });
+  describe('waitForSelectorInsideBrowser', () => {
+    it('waitForSelectorInsideBrowser should work when called with correct parameters', async () => {
+      await setupTest();
+      let percy = await Percy.start({
+        token: 'PERCY_TOKEN',
+        snapshot: { widths: [1000] },
+        discovery: { concurrency: 1 }
+      });
+      const page = await percy.browser.page();
+      spyOn(page, 'eval').and.callThrough();
+      waitForSelectorInsideBrowser(page, 'body', 30000);
+
+      expect(page.eval).toHaveBeenCalledWith('await waitForSelector("body", 30000)');
+    });
+    it('should handle errors when waitForSelectorInsideBrowser fails', async () => {
+      let error = null;
+      const expectedError = new Error('Unable to find: body');
+
+      try {
+        await waitForSelectorInsideBrowser(null, 'body', 30000);
+      } catch (e) {
+        error = e;
+      }
+
+      expect(error).toEqual(expectedError);
+    });
+  });
 });