React-to-print: Clear onload in all browsers (not just IE)?

Created on 2 Jun 2020 · 3Comments · Source: gregnb/react-to-print

Hi! This library is great, thanks so much for making it! 💖

Is there a need to only set printWindow.onload = null; in IE? Seems like that could run regardless of browser right?

https://github.com/gregnb/react-to-print/blob/a192abd07cda318b89d7eaf81198c985cde58b97/src/index.tsx#L228

Some backing context for why I'd like to remove that line: https://codesandbox.io/s/react-to-print-infinite-onloads-h4mnr infinitely hangs when running tests.

Enzyme continuously calls the printWindow's onload, even though it's only been set once.
That causes the act in the test to never complete...
- ...but the onBeforeLoad function never gets called if you use a synchronous act.

You can verify this by cloning the sandbox locally, prettifying the compiled index.js, and adding console logs.

console.log("Setting onload");
f.onload = function() {
  console.log("Calling onload");
    window.navigator && window.navigator.userAgent.indexOf("Trident/7.0") > -1 && (f.onload = null);

console.log
    Setting onload
      at e.handlePrint (node_modules/react-to-print/lib/index.js:109:35)

  console.log
    Calling onload
      at HTMLIFrameElement.f.onload (node_modules/react-to-print/lib/index.js:111:37)

  console.log
    Calling onload
      at HTMLIFrameElement.f.onload (node_modules/react-to-print/lib/index.js:111:37)

  console.log
    Calling onload
      at HTMLIFrameElement.f.onload (node_modules/react-to-print/lib/index.js:111:37)
...

Now, this seems like a bug in Enzyme and should probably be fixed there (https://github.com/enzymejs/enzyme/issues/2400), _but_ it would be fixed by this already-seemingly-positive change.

Downstream bug

Source

JoshuaKGoldberg

All 3 comments

Hi, thanks for the report. That does seem like an interesting issue. And I agree, I don't see why we can't just always clear out the event listener. I'll get it in with some changes I'm making tonight!