Firefox spelling check breaks on auto-complete pop-up

[jerrykan]

Description

Firefox's in-built check spelling feature does not work correctly when writing a new message that includes something that causes the auto-complete pop-up to appear.

Steps to reproduce

• Type an incorrectly spelt word in the "Send a message" field - observe that a red curly line appears below the word
• Keep typing a message and then try typing something that causes the auto-complete pop-up to appear (ie :D) - observe that the red curly line no longer appears below the incorrectly spelt word.

A work-around seems to be if you change to another Firefox tab, then change back again, the incorrectly spelt word is correctly highlighted.

I've notice this behaviour occurring as soon as I type a character like : and #. Interestingly If I use backspace to delete the : or # character and the space preceding it, the red curly line reappears below the incorrectly spelt word.

Version information

• Platform: web
• Browser: Firefox v74.0.1
• OS: Linux (Debian testing)
• URL: riot.im/develop (b5e8e5c-react-2929bcf9983c-js-63bc17a6b475)