I was trying to make a pack that replaces the music discs with other music and rename the discs using lang files, and I did so in 1.12.2 just fine. However, in 1.13 the game uses a .json file instead of a .lang file, and it apparently ignores everything unless the very last line is present: "realms.missing.snapshot.error.text".

If that line is not included within the lang.json file, then according to my testing it ignores the file.

Here is how I recommend lang in resource packs; No matter what language the game is in, the texture pack’s lang.json overrides that language’s lang.json.