React: Bug: "Unspecified error" some of the time in IE11 in iframe

Created on 5 Aug 2020  路  12Comments  路  Source: facebook/react

React version: 16.12

Steps To Reproduce

  1. Open http://cygnetuat.sterlingdatarooms.com/PDFTronClientTest/ in IE11
  2. Wait for the application to load in the iframe

The current behavior

Sometimes an "Unspecified error" will appear in the console and the viewer in the iframe won't load

image

Unfortunately it is not 100% reproducible. Sometimes the error won't occur. I'm also having trouble creating a minimal sample to reproduce this.

The expected behavior

There is no error.

Investigation

The relevant line in the callstack where the error is occurring is here https://github.com/facebook/react/blob/03de849af03996b7477420c97de7741ce1214149/packages/react-dom/src/client/ReactDOMInput.js#L415

I suspect it might be the same issue discussed here https://github.com/Availity/react-block-ui/issues/18

This was a real pain to track down, but apparently IE 11 will just throw Unspecified error. when accessing document.activeElement from an