feat(arx): add experimental macos support via fakedir

arx-multi-bin.patch

@@ -0,0 +1,48 @@
+diff --git a/model-scripts/tmpx.sh b/model-scripts/tmpx.sh
+index 9c2ec6f..21319d6 100755
+--- a/model-scripts/tmpx.sh
++++ b/model-scripts/tmpx.sh
+@@ -1,9 +1,10 @@
+-#!/bin/sh
++#!/usr/bin/env bash
+ set -e -u
+ unset rm_ dir
+ tmp=true ; run=true
+ tmpdir= ; rm0=true ; rm1=true ; shared=false ; hash="" # To be set by tool.
+ token=`date -u +%FT%TZ | tr -d :-`-`hexdump -n4 -e '"%08x"' </dev/urandom`
++prog_name="$0"
+ opts() {
+   cmd="$1" ; shift
+   n=$#
+@@ -39,9 +40,9 @@ opts() {
+     if $shared
+     then
+       rm_=false
+-      dir="$tmpdir"/tmpx-"$hash"
++      dir="$HOME"/.cache/tmpx-"$hash"
+     else
+-      dir="$tmpdir"/tmpx-"$token"
++      dir="$HOME"/.cache/tmpx-"$token"
+     fi
+     : ${rm_:=true}
+     if $rm_
+@@ -53,6 +54,7 @@ opts() {
+       trap 'exit 2' HUP INT QUIT BUS SEGV PIPE TERM
+     fi
+     mkdir -p "$dir"
++    export TMPX_RESTORE_PWD=$(pwd)
+     cd "$dir"
+   fi
+   # Call the command with the reassembled ARGV, options removed.
+@@ -72,7 +74,10 @@ go () {
+   fi
+   if $run
+   then
+-    ( . ../env && exec ../run "$@" )
++    (
++      . ../env
++      exec -a "${prog_name}" bash -c ". ../run" "${prog_name}" "$@"
++    )
+   fi
+ }
+ unpack_env () { : # NOOP

default.nix

@@ -1,13 +1,13 @@
-{nixpkgs ? import <nixpkgs> {}}:
+{
+  nixpkgs ? import <nixpkgs> {}
+, fakedir ? import (fetchTarball "https://github.com/nixie-dev/fakedir/archive/b0f70b805aa86fe881eeca642f12069c7983a8e7.tar.gz") {}
+}:
 
 with nixpkgs;
 
 let
   arx' = haskellPackages.arx.overrideAttrs (o: {
-    patchPhase = (o.patchPhase or "") + ''
-      substituteInPlace model-scripts/tmpx.sh \
-        --replace /tmp/ \$HOME/.cache/
-    '';
+    patches = (o.patches or []) ++ [./arx-multi-bin.patch];
   });
 in rec {
   toStorePath = target:
@@ -24,23 +24,25 @@ in rec {
     stdenv.mkDerivation {
       name = "arx";
       buildCommand = ''
-        ${arx'}/bin/arx tmpx --shared -rm! ${archive} -o $out // ${startup}
+        ${arx'}/bin/arx tmpx --shared -rm! ${archive} -o $out -e ${startup}
         chmod +x $out
       '';
     };
 
   maketar = { targets }:
     stdenv.mkDerivation {
       name = "maketar";
-      buildInputs = [ perl ];
+      buildInputs = [ perl gnutar ];
       exportReferencesGraph = map (x: [("closure-" + baseNameOf x) x]) targets;
-      buildCommand = ''
+      buildCommand = let
+        additionalPaths = lib.optionalString stdenv.isDarwin "-C ${fakedir} lib";
+      in ''
         storePaths=$(perl ${pathsFromGraph} ./closure-*)
 
         tar -cf - \
           --owner=0 --group=0 --mode=u+rw,uga+r \
           --hard-dereference \
-          $storePaths | bzip2 -z > $out
+          $storePaths ${additionalPaths} | bzip2 -z > $out
       '';
     };
 
@@ -88,18 +90,32 @@ in rec {
   let
     # Avoid re-adding a store path into the store
     path = toStorePath target;
+    script-linux = ''
+      exec .${nix-user-chroot'}/bin/nix-user-chroot -n ./nix -w ''${TMPX_RESTORE_PWD} ${nixUserChrootFlags} -- ".$(basename "$0")/$(dirname ${path}${run})" "$@"
+    '';
+    script-macos = ''
+      # use absolute paths so the environment variables don't get reinterpreted after a cd
+      __TMPX_DAT_PATH=$(pwd)
+      cd "''${TMPX_RESTORE_PWD}"
+      export DYLD_INSERT_LIBRARIES="''${__TMPX_DAT_PATH}/lib/libfakedir.dylib"
+      export FAKEDIR_PATTERN=/nix
+      export FAKEDIR_TARGET="''${__TMPX_DAT_PATH}/nix"
+
+      exec "''${__TMPX_DAT_PATH}$(basename "$0")/$(dirname ${path}${run})/$(basename "$0")" "$@"
+    '';
+    script = if stdenv.isDarwin then script-macos else script-linux;
   in
   writeScript "startup" ''
     #!/bin/sh
     ${initScript}
-    .${nix-user-chroot'}/bin/nix-user-chroot -n ./nix ${nixUserChrootFlags} -- ${path}${run} "$@"
+    ${script}
   '';
 
   nix-bootstrap = { target, extraTargets ? [], run, nix-user-chroot' ? nix-user-chroot, nixUserChrootFlags ? "", initScript ? "" }:
     let
       script = makeStartup { inherit target nixUserChrootFlags nix-user-chroot' run initScript; };
     in makebootstrap {
-      startup = ".${script} '\"$@\"'";
+      startup = script;
       targets = [ "${script}" ] ++ extraTargets;
     };
 

flake.nix

@@ -1,23 +1,40 @@
 {
   description = "The purely functional package manager";
 
-  inputs.nixpkgs.url = "nixpkgs/nixos-20.03-small";
+  inputs.nixpkgs.url = "nixpkgs/nixos-24.05-small";
+  inputs.fakedir-pkgs.url = "github:nixie-dev/fakedir";
 
-  outputs = { self, nixpkgs }: let
-    systems = [ "x86_64-linux" "i686-linux" "aarch64-linux" ];
-    forAllSystems = f: nixpkgs.lib.genAttrs systems (system: f system);
-  in {
+  outputs = { self, nixpkgs, fakedir-pkgs }: {
     bundlers = {
       nix-bundle = { program, system }: let
         nixpkgs' = nixpkgs.legacyPackages.${system};
-        nix-bundle = import self { nixpkgs = nixpkgs'; };
-        script = nixpkgs'.writeScript "startup" ''
-          #!/bin/sh
-          .${nix-bundle.nix-user-chroot}/bin/nix-user-chroot -n ./nix -- ${program} "$@"
+        fakedir = fakedir-pkgs.packages.${system}.fakedir-universal;
+        nix-bundle = import self { nixpkgs = nixpkgs'; inherit fakedir; };
+        script-linux = nixpkgs'.writeScript "startup" ''
+          #!/usr/bin/env bash
+          exec .${nix-bundle.nix-user-chroot}/bin/nix-user-chroot -n ./nix -w "''${TMPX_RESTORE_PWD}" -- "$(dirname ${program})/$(basename $0)" "$@"
         '';
+        script-darwin = nixpkgs'.writeScript "startup" ''
+          #!/usr/bin/env bash
+          # use absolute paths so the environment variables don't get reinterpreted after a cd
+          __TMPX_DAT_PATH=$(pwd)
+          cd "''${TMPX_RESTORE_PWD}"
+          export DYLD_INSERT_LIBRARIES="''${__TMPX_DAT_PATH}/lib/libfakedir.dylib"
+          export FAKEDIR_PATTERN=/nix
+          export FAKEDIR_TARGET="''${__TMPX_DAT_PATH}/nix"
+
+          # make sure the fakedir libraries are loaded by running the command in bash within the bottle
+          cmd="$(cat <<-EOH
+            ''${__TMPX_DAT_PATH}$(dirname ${program})/$(basename $0)
+          EOH
+          )"
+          args="$@"
+          exec "''${__TMPX_DAT_PATH}/${nixpkgs'.bash}/bin/bash" -c "$cmd $args"
+        '';
+        script = if nixpkgs'.stdenv.isDarwin then script-darwin else script-linux;
       in nix-bundle.makebootstrap {
         targets = [ script ];
-        startup = ".${builtins.unsafeDiscardStringContext script} '\"$@\"'";
+        startup = script;
       };
     };
 

nix-user-chroot/Makefile

@@ -1,4 +1,4 @@
 ENV_PATH ?= ""
 
 nix-user-chroot: main.cpp
-	${CXX} -o nix-user-chroot -DENV_PATH='$(ENV_PATH)' main.cpp
+	${CXX} -std=c++20 -o nix-user-chroot -DENV_PATH='$(ENV_PATH)' main.cpp