fix(page): page.click should work with disabled javascript (#2907)

Unfortunately, disabling javascript in page prevents any microtasks
to be executed even from puppeteer-originating javascript. As a
result, the IntersectionObserver hack we use to conditionally
scroll into view doesn't work.

To workaround this, we start always scrolling before clicking if
page's javascript is disabled.

Fixes #2898

lib/ElementHandle.js

@@ -55,11 +55,16 @@ class ElementHandle extends JSHandle {
   }
 
   async _scrollIntoViewIfNeeded() {
-    const error = await this.executionContext().evaluate(async element => {
+    const error = await this.executionContext().evaluate(async(element, pageJavascriptEnabled) => {
       if (!element.isConnected)
         return 'Node is detached from document';
       if (element.nodeType !== Node.ELEMENT_NODE)
         return 'Node is not of type HTMLElement';
+      // force-scroll if page's javascript is disabled.
+      if (!pageJavascriptEnabled) {
+        element.scrollIntoView({block: 'center', inline: 'center', behavior: 'instant'});
+        return false;
+      }
       const visibleRatio = await new Promise(resolve => {
         const observer = new IntersectionObserver(entries => {
           resolve(entries[0].intersectionRatio);
@@ -70,7 +75,7 @@ class ElementHandle extends JSHandle {
       if (visibleRatio !== 1.0)
         element.scrollIntoView({block: 'center', inline: 'center', behavior: 'instant'});
       return false;
-    }, this);
+    }, this, this._page._javascriptEnabled);
     if (error)
       throw new Error(error);
   }

lib/Page.js

@@ -88,6 +88,7 @@ class Page extends EventEmitter {
     this._ignoreHTTPSErrors = ignoreHTTPSErrors;
     this._coverage = new Coverage(client);
     this._defaultNavigationTimeout = 30000;
+    this._javascriptEnabled = true;
 
     this._screenshotTaskQueue = screenshotTaskQueue;
 
@@ -714,6 +715,9 @@ class Page extends EventEmitter {
    * @param {boolean} enabled
    */
   async setJavaScriptEnabled(enabled) {
+    if (this._javascriptEnabled === enabled)
+      return;
+    this._javascriptEnabled = enabled;
     await this._client.send('Emulation.setScriptExecutionDisabled', { value: !enabled });
   }
 

test/input.spec.js

@@ -28,6 +28,15 @@ module.exports.addTests = function({testRunner, expect, DeviceDescriptors}) {
       await page.click('button');
       expect(await page.evaluate(() => result)).toBe('Clicked');
     });
+    it('should click with disabled javascript', async({page, server}) => {
+      await page.setJavaScriptEnabled(false);
+      await page.goto(server.PREFIX + '/wrappedlink.html');
+      await Promise.all([
+        page.click('a'),
+        page.waitForNavigation()
+      ]);
+      expect(page.url()).toBe(server.PREFIX + '/wrappedlink.html#clicked');
+    });
 
     it('should click offscreen buttons', async({page, server}) => {
       await page.goto(server.PREFIX + '/offscreenbuttons.html');