Why write out meta.platforms?

[doronbehar]

I find this behavior peculiar:

nix-init/src/main.rs

Lines 998 to 1004 in c6e51b1

	if matches!(choice, BuildType::MkDerivation { .. }) {
	if has_zig {
	writeln!(out, " inherit (zig.meta) platforms;")?;
	} else {
	writeln!(out, " platforms = platforms.all;")?;
	}
	}

From my understanding, by default we want to support all platforms, unless upstream explicitly states that they don't intend to support other platforms, or when it is obvious from the functionality of the program (such as when it refers to the Linux kernel for example).

Inferring the later just by getting a package's URL is too much to ask from nix-init, and if all platforms should be supported, then there should be no need to write platforms = lib.platforms.all;. Also, the inheritance of (zig.meta) platforms seems unnecessary to me because that could be evaluated as so, simply because zig's build hooks should not evaluate on platforms not supported by zig. Hence in both cases stating meta.platforms seems something nix-init should not do by itself.

[AndersonTorres]

I will comment here too:

Usually specialized builders like buildPythonApp set meta.platforms since Python is not present on all platforms that Nixpkgs supports (at least in theory).

Therefore, I think this field should be treated as auto-set in cases of specialized builders.