Check if libpng = libpng12 overrides in all-packages.nix are still necessary

[Artturin]

• winhelpcgi winhelpcgi: remove override libpng #270123
• tetex tetex: remove override libpng #270107
• ploticus ploticus: remove override libpng #270146
• pngtoico pngtoico: use up-to-date libpng #269020
• sng sng: use up-to-date libpng #269022
• extremetuxracer extremetuxracer: remove override libpng #270174
• speed_dreams speed_dreams: remove override libpng #270194
• voxelands voxelands: use up-to-date libpng #269024
• xsane xsane: remove override libpng #270223

If the override is still necessary then move it directly to the default.nix with a comment about why.

[kirillrdy]

If the override is still necessary then move it directly to the default.nix with a comment about why.

may I ask why ? I though preferred way is to override in all-packages. This is also preferred way in pkgs/by-name
https://github.com/NixOS/nixpkgs/tree/master/pkgs/by-name#changing-implicit-attribute-defaults

[Artturin]

If the override is still necessary then move it directly to the default.nix with a comment about why.

may I ask why ? I though preferred way is to override in all-packages. This is also preferred way in pkgs/by-name master/pkgs/by-name#changing-implicit-attribute-defaults

Because callPackage overrides are kinda hidden and can result in confusion, the reason I created this issue was because a person on matrix was confused why one package used libpng12

[pbsds]

In preparation of the great by-name migration, doing fixes like the ones linked ^ should be encouraged for all packages in all-packages.nix. Is there a general consensus on this?

edit for future readers: i seem to be wrong

[kirillrdy]

In preparation of the great by-name migration, doing fixes like the ones linked ^ should be encouraged for all packages in all-packages.nix. Is there a general consensus on this?

No idea, i thought that this was https://github.com/NixOS/nixpkgs/tree/master/pkgs/by-name#changing-implicit-attribute-defaults
general consensus.

[pbsds]

Would this make sense, or would callPackage ignore the default?

, libpng12
, libpng ? libpng12

CC @infinisil

[infinisil]

@pbsds If libpng exists in the scope it will be passed, so the default would be ignored. (see also #131271)

[pbsds]

@Artturin, the unmerged PRs that are left all need move the libpng12 dependency into the derivation, which goes against the by-name recommendation. Do you want these merged or should we close this issue?

[Stunkymonkey]

ping @Artturin

[Artturin]

Let's close the unmerged PRs. Thanks everyone for checking if the relevant packages can use a newer libpng!