page.waitForFunction fails because of whitespace

[fringd]

Steps to reproduce

await page.waitForFunction(`
  (() => true)()`);

never returns, but

await page.waitForFunction(`(() => true)()`);

does. I expect them both to return immediately.

Tell us about your environment:

• Puppeteer version: 1.11.0
• Platform / OS version: MacOS
• URLs (if applicable):
• Node.js version: 8.9.1

[vsemozhetbyt]

It seems this is due to automatic semicolon insertion (i.e. undefined is returned) in this fragment:

https://github.com/GoogleChrome/puppeteer/blob/3d82465f667f0585ae8cb3dbb45ebe76bbc80ec7/lib/FrameManager.js#L980

cc @aslushnikov

[fringd]

this behavior is different than page.evaluate, which was rather suprising.

[fringd]

Maybe just adding parentheses would fix it? like this:

this._predicateBody = helper.isString(predicateBody) ? 'return (' + predicateBody + ')': 'return (' + predicateBody + ')(...args)'; 

[fringd]

sorry didn't mean to close.