htop: fix order or header_columns setting (#2435)

When `header_columns` is in settings it must appear before any of the
`column_meters_*` options.

Fixes 2426.

modules/programs/htop.nix

@@ -170,9 +170,18 @@ in {
         ];
       };
 
+      before = optionalAttrs (cfg.settings ? header_layout) {
+        inherit (cfg.settings) header_layout;
+      };
+
+      settings = defaults // (removeAttrs cfg.settings (attrNames before));
+
+      formatOptions = mapAttrsToList formatOption;
+
     in mkIf (cfg.settings != { }) {
-      text = concatStringsSep "\n"
-        (mapAttrsToList formatOption (defaults // cfg.settings)) + "\n";
+      text =
+        concatStringsSep "\n" (formatOptions before ++ formatOptions settings)
+        + "\n";
     };
   };
 }

tests/modules/programs/htop/default.nix

@@ -1,5 +1,6 @@
 {
   htop-empty-settings = ./empty-settings.nix;
   htop-example-settings = ./example-settings.nix;
-  settings-without-fields = ./settings-without-fields.nix;
+  htop-header_layout = ./header_layout.nix;
+  htop-settings-without-fields = ./settings-without-fields.nix;
 }

tests/modules/programs/htop/header_layout.nix

@@ -0,0 +1,37 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  config = with config.lib.htop; {
+    programs.htop.enable = true;
+    programs.htop.settings = {
+      header_layout = "two_50_50";
+      column_meters_0 = [ "AllCPUs2" "Memory" "Swap" "Zram" ];
+      column_meters_modes_0 = [ modes.Bar modes.Bar modes.Bar modes.Text ];
+      column_meters_1 = [ "Tasks" "LoadAverage" "Uptime" "Systemd" ];
+      column_meters_modes_1 = [ modes.Text modes.Text modes.Text modes.Text ];
+    };
+
+    test.stubs.htop = { };
+
+    # Test that the 'fields' key is written in addition to the customized
+    # settings or htop won't read the options.
+    nmt.script = ''
+      htoprc=home-files/.config/htop/htoprc
+      assertFileExists $htoprc
+      assertFileContent $htoprc \
+        ${
+          builtins.toFile "htoprc-expected" ''
+            header_layout=two_50_50
+            column_meters_0=AllCPUs2 Memory Swap Zram
+            column_meters_1=Tasks LoadAverage Uptime Systemd
+            column_meters_modes_0=1 1 1 2
+            column_meters_modes_1=2 2 2 2
+            fields=0 48 17 18 38 39 40 2 46 47 49 1
+          ''
+        }
+    '';
+  };
+
+}