Add a projectArgs CLI argument to hix run (#2378)

* Add a new projectArgs CLI argument to pass arguments to the hix project in the flake generated by hix run

* Use `input-output-hk/empty-flake`

* Use #2379

* Look for `projectArgs.nix`

---------

Co-authored-by: Hamish Mackenzie <Hamish.K.Mackenzie@gmail.com>

Author: demaledetti

hix/default.nix

@@ -31,9 +31,16 @@ let
       flake|build|develop|run|profile)
         # Put the flake files for remote URLs in $HOME/.hix by default
         HIX_DIR="''${HIX_DIR:-$HOME/.hix}"
+        HIX_TMPDIR="$(mktemp -d)"
+        projectArgs=""
         while(($#)); do
           arg=$1
           case $arg in
+            --projectArgs)
+              projectArgs="$2"
+              args+=(--override-input projectArgs "$HIX_TMPDIR")
+              shift
+              ;;
             --out-link|-o|--eval-store|--include|-I|--inputs-from|--expr|--file|-f|--keep|-k|--phase|--profile|--unset|-u)
               args+=("$arg" "$2")
               shift
@@ -83,7 +90,7 @@ let
         fi
         # Make a temporary flake if we have not already
         mkdir -p $FLAKE
-        HIX_FLAKE="$(mktemp -d)/flake.nix"
+        HIX_FLAKE="$HIX_TMPDIR/flake.nix"
         sed 's|EVAL_SYSTEM|${pkgs.stdenv.hostPlatform.system}|' < ${hixProject}/flake.nix > $HIX_FLAKE
         if ! cmp $HIX_FLAKE $FLAKE/flake.nix &>/dev/null; then
           if [ -e $FLAKE/flake.lock ]; then
@@ -95,6 +102,9 @@ let
           cp $HIX_FLAKE $FLAKE/flake.nix
           chmod +w $FLAKE/flake.nix
         fi
+        if [ "$projectArgs" != "" ]; then
+          printf %s "$projectArgs" > "$HIX_TMPDIR/projectArgs.nix"
+        fi
         nix $cmd "''${args[@]}"
         ;;
       init|init-hix)

hix/empty-set/default.nix

@@ -5,16 +5,21 @@
   inputs.haskellNix.url = "github:input-output-hk/haskell.nix";
   inputs.nixpkgs.follows = "haskellNix/nixpkgs-unstable";
   inputs.flake-utils.url = "github:numtide/flake-utils";
+  inputs.projectArgs.url = "github:input-output-hk/empty-flake";
+  inputs.projectArgs.flake = false;
   inputs.src.flake = false;
-  outputs = { self, src, nixpkgs, flake-utils, haskellNix }:
+  outputs = { self, src, nixpkgs, flake-utils, haskellNix, projectArgs }:
     flake-utils.lib.eachSystem [ "EVAL_SYSTEM" ] (system:
     let
       overlays = [ haskellNix.overlay
         (final: _prev: {
           hixProject =
-            final.haskell-nix.hix.project {
+            final.haskell-nix.hix.project ({
               inherit src;
-            };
+            } // (
+              if builtins.pathExists (projectArgs + "/projectArgs.nix")
+                then import (projectArgs + "/projectArgs.nix")
+                else {}));
         })
       ];
       pkgs = import nixpkgs { inherit system overlays; inherit (haskellNix) config; };