feat(page): waitForSelector hidden option (#967)

This patch adds a 'hidden' option for the `page.waitForSelector` method.

docs/api.md

@@ -1042,6 +1042,7 @@ Shortcut for [page.mainFrame().waitForFunction(pageFunction[, options[, ...args]
 - `selector` <[string]> A [selector] of an element to wait for,
 - `options` <[Object]> Optional waiting parameters
   - `visible` <[boolean]> wait for element to be present in DOM and to be visible, i.e. to not have `display: none` or `visibility: hidden` CSS properties. Defaults to `false`.
+  - `hidden` <[boolean]> wait for element to not be found in the DOM or to be hidden, i.e. have `display: none` or `visibility: hidden` CSS properties. Defaults to `false`.
   - `timeout` <[number]> maximum time to wait for in milliseconds. Defaults to `30000` (30 seconds).
 - returns: <[Promise]> Promise which resolves when element specified by selector string is added to DOM.
 

lib/FrameManager.js

@@ -413,22 +413,25 @@ class Frame {
   waitForSelector(selector, options = {}) {
     const timeout = options.timeout || 30000;
     const waitForVisible = !!options.visible;
-    const polling = waitForVisible ? 'raf' : 'mutation';
-    return this.waitForFunction(predicate, {timeout, polling}, selector, waitForVisible);
+    const waitForHidden = !!options.hidden;
+    const polling = waitForVisible || waitForHidden ? 'raf' : 'mutation';
+    return this.waitForFunction(predicate, {timeout, polling}, selector, waitForVisible, waitForHidden);
 
     /**
      * @param {string} selector
      * @param {boolean} waitForVisible
+     * @param {boolean} waitForHidden
      * @return {boolean}
      */
-    function predicate(selector, waitForVisible) {
+    function predicate(selector, waitForVisible, waitForHidden) {
       const node = document.querySelector(selector);
       if (!node)
-        return false;
-      if (!waitForVisible)
+        return waitForHidden;
+      if (!waitForVisible && !waitForHidden)
         return true;
       const style = window.getComputedStyle(node);
-      return style && style.display !== 'none' && style.visibility !== 'hidden';
+      const isVisible = style && style.display !== 'none' && style.visibility !== 'hidden';
+      return (waitForVisible === isVisible || waitForHidden === !isVisible);
     }
   }
 

test/test.js

@@ -656,12 +656,38 @@ describe('Page', function() {
     it('should wait for visible', SX(async function() {
       let divFound = false;
       const waitForSelector = page.waitForSelector('div', {visible: true}).then(() => divFound = true);
-      await page.setContent(`<div style='display: none;visibility: hidden'></div>`);
+      await page.setContent(`<div style='display: none; visibility: hidden;'></div>`);
       expect(divFound).toBe(false);
       await page.evaluate(() => document.querySelector('div').style.removeProperty('display'));
       expect(divFound).toBe(false);
       await page.evaluate(() => document.querySelector('div').style.removeProperty('visibility'));
       expect(await waitForSelector).toBe(true);
+      expect(divFound).toBe(true);
+    }));
+    it('hidden should wait for visibility: hidden', SX(async function() {
+      let divHidden = false;
+      await page.setContent(`<div style='display: block;'></div>`);
+      const waitForSelector = page.waitForSelector('div', {hidden: true}).then(() => divHidden = true);
+      await page.evaluate(() => document.querySelector('div').style.setProperty('visibility', 'hidden'));
+      expect(await waitForSelector).toBe(true);
+      expect(divHidden).toBe(true);
+    }));
+    it('hidden should wait for display: none', SX(async function() {
+      let divHidden = false;
+      await page.setContent(`<div style='display: block;'></div>`);
+      const waitForSelector = page.waitForSelector('div', {hidden: true}).then(() => divHidden = true);
+      await page.evaluate(() => document.querySelector('div').style.setProperty('display', 'none'));
+      expect(await waitForSelector).toBe(true);
+      expect(divHidden).toBe(true);
+    }));
+    it('hidden should wait for removal', SX(async function() {
+      await page.setContent(`<div></div>`);
+      let divRemoved = false;
+      const waitForSelector = page.waitForSelector('div', {hidden: true}).then(() => divRemoved = true);
+      expect(divRemoved).toBe(false);
+      await page.evaluate(() => document.querySelector('div').remove());
+      expect(await waitForSelector).toBe(true);
+      expect(divRemoved).toBe(true);
     }));
     it('should respect timeout', SX(async function() {
       let error = null;