We can't we use the

"https://launcher.mojang.com/download/linux/x86_64/minecraft-launcher_2.1.5965.tar.gz" 

url?

The flatpak uses that URL
https://github.com/flathub/com.mojang.Minecraft/blob/master/com.mojang.Minecraft.json#L65

I recommend just fetching the flathub repo and installing their desktop integrations.
Directories for those files are like this

• https://github.com/flathub/com.mojang.Minecraft/blob/master/com.mojang.Minecraft.json#L55

Thank you for the review!
As you may have noticed the .tar.gz package doesn't include icons; and I wanted to avoid depending on some third party repository for our build, but we may have to if we don't get a permalink to the .deb.

To use the tar.gz url, since there's only a single icon (that probably won't ever change), we can just embed it as nixpkgs/pkgs/games/minecraft/minecraft-launcher.svg, and for the desktop item we can use makeDesktopItem.

I think this json file has links to the launcher files

• https://launchermeta.mojang.com/mc/launcher.json

I see no mention of a permalink for a debian file. Perhaps looking at an ubuntu ppa could yield some info. I've also looked at all references to minecraft launcher on repology and they either use that link to the debian file, the one I've mentioned, or completely vendor the binary. I don't think we technically lose anything from fetching the files from flathub, it would be much worse to add them in tree.
Not to mention the icon in the debian file isn't exactly very valuable, it's just one and symbolic, flathub has better data there anyway.

That JSON URL seems pretty useful to write an update script!

What we do lose by fetching from flathub is the ability for the build to succeed even if flathub doesn't provide those files anymore.
I looked at the terms provided by Mojang and couldn't find something that unambiguously grants us the right to redistribute the icon, [EDIT: so I wouldn't want to embed it in the repository like @infinisil suggested,] but I'm not really well versed in legal stuff.

We don't distribute this. And it's a git repo, only thing you'd worry about is it being completely deleted.
And then you could vendor the meta data. Also not sure if that's even the icon used by them and not custom one's. Technical viewpoint, it's very cheap to just fetch another repo.

See #68123 (comment). We should switch the launchers license from unfreeRedistributable (which never actually worked anyways) to unfree. And we can't fetch from flatpack because what they're doing isn't technically legal.

For the icon, @peterix indicated an offer to put it at an official url for grabs.

Is this just about the official minecraft icon? If it's the same as the website, you could always fetch the archived version from today by archive.org. IANAL but I think their archiving and us fetching said archive is both perfectly legal (as long as we don't redistribute).

If it's the same as the website

Unfortunately not, we need the transparency. But it looks like we'll get a fixed path to the icon or something that includes it.

@infinisil are you still waiting for upstream, for the icon?

That would be nice yeah, I'm not sure if there's a legally correct way to get the icon without it

Here you go:

$ wget https://launcher.mojang.com/download/minecraft-launcher.svg
$ sha256sum minecraft-launcher.svg

35c2bcaeb09fa4b8864e9422fd66bf60847706f8b4400ec4a66ba6436b101f71 minecraft-launcher.svg

$ sha1sum minecraft-launcher.svg

387fbc45b62412fcb75f8611a9f889d3418fd954 minecraft-launcher.svg

$ md5sum minecraft-launcher.svg

0b104e3049346908bf559cab602071e3 minecraft-launcher.svg

Thanks a lot! ❤️

Thanks a lot @peterix!
I added an update script to check the latest version on AUR, since that JSON API from mojang.com lists an outdated one.
From my side this is ready to merge.

Backported to 19.09 in 10903f5

Is 19.03 affected?

Yeah, I'll backport to 19.03 too

Backported to 19.03 in 7086c81