kakoune: implement whitespace highlighter config

The options under `programs.kakoune.config.showWhitespace` existed
but were not implemented.

PR #1162

modules/programs/kakoune.nix

@@ -513,6 +513,15 @@ let
         "${optionalString (separator != null) " -separator ${separator}"}"
       ];
 
+    showWhitespaceOptions = with cfg.config.showWhitespace;
+      concatStrings [
+        (optionalString (tab != null) " -tab ${tab}")
+        (optionalString (tabStop != null) " -tabpad ${tabStop}")
+        (optionalString (space != null) " -spc ${space}")
+        (optionalString (nonBreakingSpace != null) " -nbsp ${nonBreakingSpace}")
+        (optionalString (lineFeed != null) " -lf ${lineFeed}")
+      ];
+
     uiOptions = with cfg.config.ui;
       concatStringsSep " " [
         "ncurses_set_title=${if setTitle then "true" else "false"}"
@@ -572,6 +581,8 @@ let
         ++ optional (numberLines != null && numberLines.enable)
         "add-highlighter global/ number-lines${numberLinesOptions}"
         ++ optional showMatching "add-highlighter global/ show-matching"
+        ++ optional (showWhitespace != null && showWhitespace.enable)
+        "add-highlighter global/ show-whitespaces${showWhitespaceOptions}"
         ++ optional (scrollOff != null)
         "set-option global scrolloff ${toString scrollOff.lines},${
           toString scrollOff.columns

tests/default.nix

@@ -32,6 +32,7 @@ import nmt {
     ./modules/programs/fish
     ./modules/programs/git
     ./modules/programs/gpg
+    ./modules/programs/kakoune
     ./modules/programs/lieer
     ./modules/programs/mbsync
     ./modules/programs/neomutt

tests/modules/programs/kakoune/default.nix

@@ -0,0 +1 @@
+{ kakoune-whitespace-highlighter = ./whitespace-highlighter.nix; }

tests/modules/programs/kakoune/whitespace-highlighter.nix

@@ -0,0 +1,32 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  config = {
+    programs.kakoune = {
+      enable = true;
+      config.showWhitespace = {
+        enable = true;
+        lineFeed = "1";
+        space = "2";
+        nonBreakingSpace = "3";
+        tab = "4";
+        tabStop = "5";
+      };
+    };
+
+    nmt.script = let
+      lineStart =
+        "^add-highlighter\\s\\+global\\/\\?\\s\\+show-whitespaces\\s\\+"
+        + "\\(-\\w\\+\\s\\+.\\s\\+\\)*";
+    in ''
+      assertFileExists home-files/.config/kak/kakrc
+      assertFileRegex home-files/.config/kak/kakrc '${lineStart}-lf\s\+1\b'
+      assertFileRegex home-files/.config/kak/kakrc '${lineStart}-spc\s\+2\b'
+      assertFileRegex home-files/.config/kak/kakrc '${lineStart}-nbsp\s\+3\b'
+      assertFileRegex home-files/.config/kak/kakrc '${lineStart}-tab\s\+4\b'
+      assertFileRegex home-files/.config/kak/kakrc '${lineStart}-tabpad\s\+5\b'
+    '';
+  };
+}