The panel that closed itself

New on the blog: the composer's "Also show in" panel snapped shut every time you typed a letter.

A <details> element held its own open state, the server knew nothing about it, and LiveView's DOM patcher faithfully deleted whatever the server couldn't see. The patcher did it — and it still wasn't wrong.

https://jva.lol/weblog/the-panel-that-closed-itself/

It's the sequel to The panel that hid itself, where the patcher was the obvious suspect and came back innocent. Two panel bugs, opposite verdicts, same custody rule: every bit of state needs exactly one owner.

(Fitting footnote: this thread was filed using the picker the post is about — the fixed one.)