tclPackages: define tcl8Packages and tcl9Packages

[ghost]

It should be possible to build packages against Tcl-9, regardless if stubs are present in extensions.

Ping @fgaz

Things done

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.

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[fgaz]

This is going to make the tcl9 update much easier, thanks!

Please mention the package sets in doc/languages-frameworks/tcl.section.md like it's done in the python section and add an entry to the release notes

[fgaz]

Let's keep a comment like this to explain why we don't also have minor versions:

Suggested change

	# We don't need versioned package sets thanks to the tcl stubs mechanism
	# We don't need versioned package sets for minor versions thanks to the tcl stubs mechanism

[fgaz]

For consistency with the other sets, I think we should either expose the versioned or the unversioned set, not both

Suggested change

	tclPackages = tcl8Packages;
	tclPackages = dontRecurseIntoAttrs tcl8Packages;

[ghost]

I agree, but how should callPackage select a set for "applications"?

How about this?

{ lib
, tclPackages ? tcl9Packages,
, tcl9Packages
}: null

[fgaz]

I'm not sure I understand your question. recurseIntoAttrs/dontRecurseIntoAttrs is just a hint for nix search / https://search.nixos.org / other tools. The package set is still available for use in nix code, it's just hidden from display in some places.

[ghost]

The question is how should packages outside the scope of a tclNPackages bring one into scope. Things like Tcl/Tk applications.

[fgaz]

Sorry, I missed the notification ^_^"

As far as I can see with other ecosystems we use the unversioned set by default unless the program does not compile with the default version. We can do the same.