Whenever an invalid sound file is played, the game freezes, without any error message whatsoever.
Steps to reproduce:
Download the attached resource pack.
Enable it in-game.
Use
/playsound minecraft:totallyavalidsound.txt master @p
Game freezes.
The game should abort and throw an error instead.
Additional debug info (17w06a):
WhatIsHang
jstack -l
jstack -m (tool breaks)
jstack -F -m (tool breaks)