treewide: use perl.withPackages when possible

Since 03eaa48 added perl.withPackages, there is a canonical way to
create a perl interpreter from a list of libraries, for use in script
shebangs or generic build inputs. This method is declarative (what we
are doing is clear), produces short shebangs[1] and needs not to wrap
existing scripts.

Unfortunately there are a few exceptions that I've found:

  1. Scripts that are calling perl with the -T switch. This makes perl
  ignore PERL5LIB, which is what perl.withPackages is using to inform
  the interpreter of the library paths.

  2. Perl packages that depends on libraries in their own path. This
  is not possible because perl.withPackages works at build time. The
  workaround is to add `-I $out/${perl.libPrefix}` to the shebang.

In all other cases I propose to switch to perl.withPackages.

[1]: https://lwn.net/Articles/779997/

9 files changed, 15 insertions, 16 deletions

diff --git a/nixos/modules/config/users-groups.nix b/nixos/modules/config/users-groups.nix
index 1a530b9f013..1da150148b2 100644
--- a/nixos/modules/config/users-groups.nix
+++ b/nixos/modules/config/users-groups.nix
@@ -556,10 +556,8 @@ in {
         install -m 0700 -d /root
         install -m 0755 -d /home
 
-        ${pkgs.perl}/bin/perl -w \
-          -I${pkgs.perlPackages.FileSlurp}/${pkgs.perl.libPrefix} \
-          -I${pkgs.perlPackages.JSON}/${pkgs.perl.libPrefix} \
-          ${./update-users-groups.pl} ${spec}
+        ${pkgs.perl.withPackages (p: [ p.FileSlurp p.JSON ])}/bin/perl \
+        -w ${./update-users-groups.pl} ${spec}
       '';
 
     # for backwards compatibility
diff --git a/nixos/modules/installer/tools/tools.nix b/nixos/modules/installer/tools/tools.nix
index a9e5641b05a..77c974fc22c 100644
--- a/nixos/modules/installer/tools/tools.nix
+++ b/nixos/modules/installer/tools/tools.nix
@@ -34,7 +34,7 @@ let
     name = "nixos-generate-config";
     src = ./nixos-generate-config.pl;
     path = lib.optionals (lib.elem "btrfs" config.boot.supportedFilesystems) [ pkgs.btrfs-progs ];
-    perl = "${pkgs.perl}/bin/perl -I${pkgs.perlPackages.FileSlurp}/${pkgs.perl.libPrefix}";
+    perl = "${pkgs.perl.withPackages (p: [ p.FileSlurp ])}/bin/perl";
     inherit (config.system.nixos-generate-config) configuration desktopConfiguration;
     xserverEnabled = config.services.xserver.enable;
   };
diff --git a/nixos/modules/programs/command-not-found/command-not-found.nix b/nixos/modules/programs/command-not-found/command-not-found.nix
index d8394bf73a2..79786584c66 100644
--- a/nixos/modules/programs/command-not-found/command-not-found.nix
+++ b/nixos/modules/programs/command-not-found/command-not-found.nix
@@ -14,10 +14,8 @@ let
     dir = "bin";
     src = ./command-not-found.pl;
     isExecutable = true;
-    inherit (pkgs) perl;
     inherit (cfg) dbPath;
-    perlFlags = concatStrings (map (path: "-I ${path}/${pkgs.perl.libPrefix} ")
-      [ pkgs.perlPackages.DBI pkgs.perlPackages.DBDSQLite pkgs.perlPackages.StringShellQuote ]);
+    perl = pkgs.perl.withPackages (p: [ p.DBDSQLite p.StringShellQuote ]);
   };
 
 in
diff --git a/nixos/modules/programs/command-not-found/command-not-found.pl b/nixos/modules/programs/command-not-found/command-not-found.pl
index 7515dd975c3..6e275bcc8be 100644
--- a/nixos/modules/programs/command-not-found/command-not-found.pl
+++ b/nixos/modules/programs/command-not-found/command-not-found.pl
@@ -1,4 +1,4 @@
-#! @perl@/bin/perl -w @perlFlags@
+#! @perl@/bin/perl -w
 
 use strict;
 use DBI;
diff --git a/nixos/modules/system/activation/switch-to-configuration.pl b/nixos/modules/system/activation/switch-to-configuration.pl
index b82d69b3bb8..8bd85465472 100644
--- a/nixos/modules/system/activation/switch-to-configuration.pl
+++ b/nixos/modules/system/activation/switch-to-configuration.pl
@@ -1,4 +1,4 @@
-#! @perl@
+#! @perl@/bin/perl
 
 use strict;
 use warnings;
diff --git a/nixos/modules/system/activation/top-level.nix b/nixos/modules/system/activation/top-level.nix
index b0f77ca3fb8..9dbca4e33f3 100644
--- a/nixos/modules/system/activation/top-level.nix
+++ b/nixos/modules/system/activation/top-level.nix
@@ -113,8 +113,7 @@ let
     configurationName = config.boot.loader.grub.configurationName;
 
     # Needed by switch-to-configuration.
-
-    perl = "${pkgs.perl}/bin/perl " + (concatMapStringsSep " " (lib: "-I${lib}/${pkgs.perl.libPrefix}") (with pkgs.perlPackages; [ FileSlurp NetDBus XMLParser XMLTwig ]));
+    perl = pkgs.perl.withPackages (p: with p; [ FileSlurp NetDBus XMLParser XMLTwig ]);
   };
 
   # Handle assertions and warnings
diff --git a/nixos/modules/system/boot/loader/grub/grub.nix b/nixos/modules/system/boot/loader/grub/grub.nix
index 289c2b19986..c6ec9acd54c 100644
--- a/nixos/modules/system/boot/loader/grub/grub.nix
+++ b/nixos/modules/system/boot/loader/grub/grub.nix
@@ -728,13 +728,17 @@ in
             utillinux = pkgs.util-linux;
             btrfsprogs = pkgs.btrfs-progs;
           };
+          perl = pkgs.perl.withPackages (p: with p; [
+            FileSlurp FileCopyRecursive
+            XMLLibXML XMLSAX XMLSAXBase
+            ListCompare JSON
+          ]);
         in pkgs.writeScript "install-grub.sh" (''
         #!${pkgs.runtimeShell}
         set -e
-        export PERL5LIB=${with pkgs.perlPackages; makePerlPath [ FileSlurp FileCopyRecursive XMLLibXML XMLSAX XMLSAXBase ListCompare JSON ]}
         ${optionalString cfg.enableCryptodisk "export GRUB_ENABLE_CRYPTODISK=y"}
       '' + flip concatMapStrings cfg.mirroredBoots (args: ''
-        ${pkgs.perl}/bin/perl ${install-grub-pl} ${grubConfig args} $@
+        ${perl}/bin/perl ${install-grub-pl} ${grubConfig args} $@
       '') + cfg.extraInstallCommands);
 
       system.build.grub = grub;
diff --git a/nixos/modules/system/etc/etc.nix b/nixos/modules/system/etc/etc.nix
index 7478e3e8071..a450f303572 100644
--- a/nixos/modules/system/etc/etc.nix
+++ b/nixos/modules/system/etc/etc.nix
@@ -154,7 +154,7 @@ in
       ''
         # Set up the statically computed bits of /etc.
         echo "setting up /etc..."
-        ${pkgs.perl}/bin/perl -I${pkgs.perlPackages.FileSlurp}/${pkgs.perl.libPrefix} ${./setup-etc.pl} ${etc}/etc
+        ${pkgs.perl.withPackages (p: [ p.FileSlurp ])}/bin/perl ${./setup-etc.pl} ${etc}/etc
       '';
 
   };
diff --git a/nixos/modules/testing/service-runner.nix b/nixos/modules/testing/service-runner.nix
index 76e9d4a68c4..9060be3cca1 100644
--- a/nixos/modules/testing/service-runner.nix
+++ b/nixos/modules/testing/service-runner.nix
@@ -6,7 +6,7 @@ let
 
   makeScript = name: service: pkgs.writeScript "${name}-runner"
     ''
-      #! ${pkgs.perl}/bin/perl -w -I${pkgs.perlPackages.FileSlurp}/${pkgs.perl.libPrefix}
+      #! ${pkgs.perl.withPackages (p: [ p.FileSlurp ])}/bin/perl -w
 
       use File::Slurp;