envfs: init at 1.0.0

nixos/modules/module-list.nix

@@ -1311,6 +1311,7 @@
   ./tasks/filesystems/btrfs.nix
   ./tasks/filesystems/cifs.nix
   ./tasks/filesystems/ecryptfs.nix
+  ./tasks/filesystems/envfs.nix
   ./tasks/filesystems/exfat.nix
   ./tasks/filesystems/ext.nix
   ./tasks/filesystems/f2fs.nix

nixos/modules/tasks/filesystems/envfs.nix

@@ -0,0 +1,51 @@
+{ pkgs, config, lib, ... }:
+
+let
+  cfg = config.services.envfs;
+  mounts = {
+    "/usr/bin" = {
+      device = "none";
+      fsType = "envfs";
+      options = [
+        "fallback-path=${pkgs.runCommand "fallback-path" {} ''
+          mkdir -p $out
+          ln -s ${pkgs.coreutils}/bin/env $out/env
+          ln -s ${config.system.build.binsh}/bin/sh $out/sh
+        ''}"
+      ];
+    };
+    "/bin" = {
+      device = "/usr/bin";
+      fsType = "none";
+      options = [ "bind" ];
+    };
+  };
+in {
+  options = {
+    services.envfs = {
+      enable = lib.mkEnableOption (lib.mdDoc "Envfs filesystem") // {
+        description = lib.mdDoc ''
+          Fuse filesystem that returns symlinks to executables based on the PATH
+          of the requesting process. This is useful to execute shebangs on NixOS
+          that assume hard coded locations in locations like /bin or /usr/bin
+          etc.
+        '';
+      };
+      package = lib.mkOption {
+        type = lib.types.package;
+        description = lib.mdDoc "Which package to use for the envfs.";
+        default = pkgs.envfs;
+        defaultText = lib.mdDoc "pkgs.envfs";
+      };
+    };
+  };
+  config = lib.mkIf (cfg.enable) {
+    environment.systemPackages = [ cfg.package ];
+    # we also want these mounts in virtual machines.
+    fileSystems = if config.virtualisation ? qemu then lib.mkVMOverride mounts else mounts;
+
+    # We no longer need those when using envfs
+    system.activationScripts.usrbinenv = lib.mkForce "";
+    system.activationScripts.binsh = lib.mkForce "";
+  };
+}

nixos/tests/all-tests.nix

@@ -195,6 +195,7 @@ in {
   engelsystem = handleTest ./engelsystem.nix {};
   enlightenment = handleTest ./enlightenment.nix {};
   env = handleTest ./env.nix {};
+  envfs = handleTest ./envfs.nix {};
   envoy = handleTest ./envoy.nix {};
   ergo = handleTest ./ergo.nix {};
   ergochat = handleTest ./ergochat.nix {};

nixos/tests/envfs.nix

@@ -0,0 +1,42 @@
+import ./make-test-python.nix ({ lib, pkgs, ... }:
+let
+  pythonShebang = pkgs.writeScript "python-shebang" ''
+    #!/usr/bin/python
+    print("OK")
+  '';
+
+  bashShebang = pkgs.writeScript "bash-shebang" ''
+    #!/usr/bin/bash
+    echo "OK"
+  '';
+in
+{
+  name = "envfs";
+  nodes.machine.services.envfs.enable = true;
+
+  testScript = ''
+    start_all()
+    machine.wait_until_succeeds("mountpoint -q /usr/bin/")
+    machine.succeed(
+        "PATH=${pkgs.coreutils}/bin /usr/bin/cp --version",
+        # check fallback paths
+        "PATH= /usr/bin/sh --version",
+        "PATH= /usr/bin/env --version",
+        "PATH= test -e /usr/bin/sh",
+        "PATH= test -e /usr/bin/env",
+        # no stat
+        "! test -e /usr/bin/cp",
+        # also picks up PATH that was set after execve
+        "! /usr/bin/hello",
+        "PATH=${pkgs.hello}/bin /usr/bin/hello",
+    )
+
+    out = machine.succeed("PATH=${pkgs.python3}/bin ${pythonShebang}")
+    print(out)
+    assert out == "OK\n"
+
+    out = machine.succeed("PATH=${pkgs.bash}/bin ${bashShebang}")
+    print(out)
+    assert out == "OK\n"
+  '';
+})

pkgs/tools/filesystems/envfs/default.nix

@@ -0,0 +1,28 @@
+{ rustPlatform, lib, fetchFromGitHub, nixosTests }:
+rustPlatform.buildRustPackage rec {
+  pname = "envfs";
+  version = "1.0.0";
+  src = fetchFromGitHub {
+    owner = "Mic92";
+    repo = "envfs";
+    rev = version;
+    hash = "sha256-aF8V1LwPGifFWoVxM0ydOnTX1pDVJ6HXevTxADJ/rsw=";
+  };
+  cargoHash = "sha256-kw56tbe5zvWY5bI//dUqR1Rlumz8kOG4HeXiyEyL0I0=";
+
+  passthru.tests = {
+    envfs = nixosTests.envfs;
+  };
+
+  postInstall = ''
+    ln -s envfs $out/bin/mount.envfs
+    ln -s envfs $out/bin/mount.fuse.envfs
+  '';
+  meta = with lib; {
+    description = "Fuse filesystem that returns symlinks to executables based on the PATH of the requesting process.";
+    homepage = "https://github.com/Mic92/envfs";
+    license = licenses.mit;
+    maintainers = with maintainers; [ mic92 ];
+    platforms = platforms.linux;
+  };
+}

pkgs/top-level/all-packages.nix

@@ -4405,6 +4405,8 @@ with pkgs;
 
   envsubst = callPackage ../tools/misc/envsubst { };
 
+  envfs = callPackage ../tools/filesystems/envfs { };
+
   er-patcher = callPackage ../tools/games/er-patcher { };
 
   errcheck = callPackage ../development/tools/errcheck { };