[wp-trac] [WordPress Trac] #49519: Regression: IE11 block editor error when deleting a block using the keyboard

[WordPress Trac]

#49519: Regression: IE11 block editor error when deleting a block using the
keyboard
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 Reporter:  afercia                      |       Owner:  (none)
     Type:  defect (bug)                 |      Status:  new
 Priority:  normal                       |   Milestone:  5.4
Component:  Editor                       |     Version:  trunk
 Severity:  normal                       |  Resolution:
 Keywords:  needs-patch has-screenshots  |     Focuses:
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Comment (by aduth):

 I haven't been able to pinpoint the exact cause yet, and especially why it
 would only impact Internet Explorer, but I suspect the issue occurs here
 in code:

 https://github.com/WordPress/gutenberg/blob/d026d5b/packages/rich-
 text/src/component/index.js#L1145

 React "Refs" are a common source of these sorts of errors, considering how
 they are assigned only after the component's first render, and unassigned
 when the component unmounts:

 https://reactjs.org/docs/refs-and-the-dom.html#adding-a-ref-to-a-dom-
 element

 Typically it is a good practice to verify that the ref is assigned before
 referencing any of its properties, since otherwise errors like the one in
 the original report can occur.

 However, it is yet unclear to me:

 - Was there some expected guarantee that the ref would always be assigned
 if this event handler is reached?
 - Why does it only happen in Internet Explorer?
 - Would including a guarded condition on the assigned ref break expected
 behavior of this focus handler?

 Related pull request (cc @iseulde @jorgefilipecosta):

 https://github.com/WordPress/gutenberg/pull/19536

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Ticket URL: <https://core.trac.wordpress.org/ticket/49519#comment:1>
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