buildLuarocksPackage: cannot build package that depends on luarocks

[mrcjkb]

Describe the bug

luarocks exists as a luarocks package that other luarocks packages can depend on.
When trying to build a rockspec that depends on luarocks with buildLuarocksPackage, it fails.

-- rockspec dependencies
dependencies = {
  "lua >= 5.1",
  "luarocks",
}

       > Running phase: installPhase
       > Missing dependencies for testpackage scm-1:
       >    luarocks (not installed)
       >
       > testpackage scm-1 depends on lua >= 5.1 (5.1-1 provided by VM: success)
       > testpackage scm-1 depends on luarocks (not installed)
       > Warning: Failed searching manifest: Failed downloading https://luarocks.org/manifest-5.1 - no downloader tool available, 
please install wget or curl in your system
       >
       > Error: Could not satisfy dependency luarocks: No results matching query were found for Lua 5.1.
       For full logs, run 'nix log /nix/store/rnbmdmw05596619d3nsvzrwflqxh6gi6-lua5.1-testpackage-scm-1.drv'.

The rocks_trees entry in the generated luarocks config contains an entry for luarocks, but luarocks doesn't recognise it and tries to download the package instead.

Steps To Reproduce

I have created a repository to reproduce it with: https://github.com/mrcjkb/nix-luarocks-repro

• Run nix build .#testpackage

A workaround is to use luarocks-nix to generate a buildLuarocksPackage expression for luarocks (luarocks nix luarocks),
and to add that package to the testpackage's propagatedBuildInputs instead of the luarocks package from nixpkgs.

Notify maintainers

@teto

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[teto]

thanks for creating the test repo, it's helpful. I've looked at the generated LUAROCKS_CONFIG and all looks good and I think luarocks just doesn't recognize the installed luarocks because of luarocks/luarocks#1659

My first thought would have been to rename the current luarocks into a luarocks_bootstrap and add a generated luarocks derivation, for which we could run the tests without the cyclic dependency luarocks -> busted -> luarocks.
While this might be the best outcome longterm, I am looking into the quickfix which would be to generate the manifest for the current luarocks