fix: less confusing error message (#2305)

Fixes #2283

Author: aslushnikov

src/frames.ts

@@ -451,7 +451,7 @@ export class Frame {
 
     const deadline = this._page._timeoutSettings.computeDeadline(options);
     const { world, task } = selectors._waitForSelectorTask(selector, state, deadline);
-    const result = await this._scheduleRerunnableTask(task, world, deadline, `selector "${selectorToString(selector, state)}"`);
+    const result = await this._scheduleRerunnableTask(task, world, deadline, `selector "${selector}"${state === 'attached' ? '' : ' to be ' + state}`);
     if (!result.asElement()) {
       result.dispose();
       return null;
@@ -469,7 +469,7 @@ export class Frame {
   async dispatchEvent(selector: string, type: string, eventInit?: Object, options?: types.TimeoutOptions): Promise<void> {
     const deadline = this._page._timeoutSettings.computeDeadline(options);
     const task = selectors._dispatchEventTask(selector, type, eventInit || {}, deadline);
-    const result = await this._scheduleRerunnableTask(task, 'main', deadline, `selector "${selectorToString(selector, 'attached')}"`);
+    const result = await this._scheduleRerunnableTask(task, 'main', deadline, `selector "${selector}"`);
     result.dispose();
   }
 
@@ -970,17 +970,6 @@ class RerunnableTask {
   }
 }
 
-function selectorToString(selector: string, state: 'attached' | 'detached' | 'visible' | 'hidden'): string {
-  let label;
-  switch (state) {
-    case 'visible': label = '[visible] '; break;
-    case 'hidden': label = '[hidden] '; break;
-    case 'attached': label = ''; break;
-    case 'detached': label = '[detached]'; break;
-  }
-  return `${label}${selector}`;
-}
-
 export class SignalBarrier {
   private _options: types.NavigatingActionWaitOptions;
   private _protectCount = 0;

test/waittask.spec.js

@@ -341,7 +341,7 @@ describe('Frame.waitForSelector', function() {
     let error = null;
     await page.waitForSelector('div', { state: 'hidden', timeout: 1000 }).catch(e => error = e);
     expect(error).toBeTruthy();
-    expect(error.message).toContain('waiting for selector "[hidden] div" failed: timeout');
+    expect(error.message).toContain('waiting for selector "div" to be hidden failed: timeout');
   });
   it('should respond to node attribute mutation', async({page, server}) => {
     let divFound = false;