Can't select navigation block if first clicking canvas

[jasmussen]

Steps to reproduce:

1. Insert a navigation block. Vertical or horizontal, doesn't matter.
2. Click "Start Empty".
3. Click outside the editing canvas, for example to the right of post content, to deselect all blocks.
4. Click the navigation block to select it.

Observe that the navigation block receives focus (as indicated by the blue border), but is not selected. So neither the block toolbar appears, or the is-selected CSS class is present.

Note that if instead of clicking outside the editing canvas, you select a different block, you can select the navigation block.

I wasn't able to reproduce this issue with any other blocks than Navigation, it doesn't seem like this would be limited to just this block. But it does appear to be related to nesting.

GIF showing the above:

Chatted yesterday with @gziolo, @ellatrix and @retrofox, and it was suggested that AsyncModeProvider could theoretically be related to the cause of the issue. It's the cause of this adjacent Safari-only bug: #19454.

[ZebulanStanphill]

I recently ran into a very similar (if not the same) issue after rebasing #21234: my Table of Contents block PR. Notably, both blocks use <nav>, <ul>, and <li> elements, so maybe that's related somehow?

[jasmussen]

I had the same thought, and in a shotgun debugging session, I tried replacing all those with divs. Alas, no change.

[ntsekouras]

@jasmussen I couldn't reproduce this. Is this still happening?

[jasmussen]

Hallelujah, no, it appears fixed!

[jasmussen]

Ack, I'm seeing it again. Reopening. Same steps to reproduce.

[jasmussen]

This one is potentially related: #29678