Yes, building with Hugs is currently the preferred way because it does not depend on any pre-generated code.
The stage 1 build uses a pre-existing mhs (usually runhugs wrapped mhs) with make.
The stage 2 build uses the stage 1 mhs with mcabal.

It's not immediately obvious to me how exactly mhseval.js is generated, but is there any reason you can't generate it using the stage 1 or stage 2 compiler?

I was trying to get it to work via

mhseval = pkgs.haskell.compiler.microhs.overrideAttrs (prevAttrs: {
  microhs-stage1 = prevAttrs.passthru.microhs-stage1.overrideAttrs {
    nativeBuildInputs = [ pkgs.breakpointHook ];
    postBuild = ''
      make bin/mhseval
    '';
    postInstall = ''
      cp bin/mhseval $out/bin/mhseval
    '';
  };
});

and didn't manage to get a useful output that way, I did try to copy it from stage1 to stage2 later, but I've changed a bunch of code around this

I'm starting out with nix and having trouble with system library fiddling. GHC cannot load the shared object for z3, though the C headers are found just fine.
This is my flake definition:

{
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs { inherit system; };
	in {
		devShells.default = with pkgs; mkShell
		{
			packages =
				[ haskell.compiler.ghc914
				  z3
				  stack
				  libllvm
				  libclang
				];
		};
	}
	);
}

can we improve the whole security_tool issue for mac builds?

https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/haskell-modules/configuration-darwin.nix is littered with

• dontCheck that, well, makes us not run tests
• substituteInPlace System/X509/MacOS.hs --replace-fail security /usr/bin/security that breaks sandbox builds

I also run into it for some packages on darwin pkgsStatic builds somehow due to the iserv-proxy thing

statistics> [33 of 51] Compiling Statistics.Types ( Statistics/Types.hs, dist/build/Statistics/Types.o )
statistics> iserv-proxy: Uncaught exception ghc-internal:GHC.Internal.IO.Exception.IOException:
statistics>
statistics> /homeless-shelter/Library/Frameworks/Security.framework/Security: withBinaryFile: does not exist (No such file or directory)
statistics>
statistics> HasCallStack backtrace:
statistics>   ioError, called at libraries/ghc-internal/src/GHC/Internal/Foreign/C/Error.hs:291:5 in ghc-internal:GHC.Internal.Foreign.C.Error
statistics>
statistics> <no location info>: error: External interpreter terminated (1)

can we improve the whole security_tool issue for mac builds?

https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/haskell-modules/configuration-darwin.nix is littered with

• dontCheck that, well, makes us not run tests
• substituteInPlace System/X509/MacOS.hs --replace-fail security /usr/bin/security that breaks sandbox builds

I also run into it for some packages on darwin pkgsStatic.haskellPackages builds somehow via iserv-proxy

statistics> [33 of 51] Compiling Statistics.Types ( Statistics/Types.hs, dist/build/Statistics/Types.o )
statistics> iserv-proxy: Uncaught exception ghc-internal:GHC.Internal.IO.Exception.IOException:
statistics>
statistics> /homeless-shelter/Library/Frameworks/Security.framework/Security: withBinaryFile: does not exist (No such file or directory)
statistics>
statistics> HasCallStack backtrace:
statistics>   ioError, called at libraries/ghc-internal/src/GHC/Internal/Foreign/C/Error.hs:291:5 in ghc-internal:GHC.Internal.Foreign.C.Error
statistics>
statistics> <no location info>: error: External interpreter terminated (1)

In reply to @alexfmpe:matrix.org

can we improve the whole security_tool issue for mac builds?

https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/haskell-modules/configuration-darwin.nix is littered with

• dontCheck that, well, makes us not run tests
• substituteInPlace System/X509/MacOS.hs --replace-fail security /usr/bin/security that breaks sandbox builds

I also run into it for some packages on darwin pkgsStatic builds somehow due to the iserv-proxy thing

statistics> [33 of 51] Compiling Statistics.Types ( Statistics/Types.hs, dist/build/Statistics/Types.o )
statistics> iserv-proxy: Uncaught exception ghc-internal:GHC.Internal.IO.Exception.IOException:
statistics>
statistics> /homeless-shelter/Library/Frameworks/Security.framework/Security: withBinaryFile: does not exist (No such file or directory)
statistics>
statistics> HasCallStack backtrace:
statistics>   ioError, called at libraries/ghc-internal/src/GHC/Internal/Foreign/C/Error.hs:291:5 in ghc-internal:GHC.Internal.Foreign.C.Error
statistics>
statistics> <no location info>: error: External interpreter terminated (1)