kakoune: escape showWhitespace separators

We were passing the separators for the `show-whitespaces` highlighter
verbatim. This was problematic in case one wanted to use, spaces,
quotes or `%` as separators since the resulting kakoune configuration
would be invalid.

According to kakoune's docs, the separator has to be one character
long, so we can use a simple rule for escaping them. It is possible
that people has been working this around by passing, e.g. `"' '"` as
separator in order to get a space (i.e., escaped explicitly by the
user), so we just let longer strings be used verbatim.

PR #1357

modules/programs/kakoune.nix

@@ -506,12 +506,22 @@ let
       ];
 
     showWhitespaceOptions = with cfg.config.showWhitespace;
-      concatStrings [
+      let
-        (optionalString (tab != null) " -tab ${tab}")
+        quoteSep = sep:
-        (optionalString (tabStop != null) " -tabpad ${tabStop}")
+          if sep == "'" then
-        (optionalString (space != null) " -spc ${space}")
+            ''"'"''
-        (optionalString (nonBreakingSpace != null) " -nbsp ${nonBreakingSpace}")
+          else if lib.strings.stringLength sep == 1 then
-        (optionalString (lineFeed != null) " -lf ${lineFeed}")
+            "'${sep}'"
+          else
+            sep; # backwards compat, in case sep == "' '", etc.
+
+      in concatStrings [
+        (optionalString (tab != null) " -tab ${quoteSep tab}")
+        (optionalString (tabStop != null) " -tabpad ${quoteSep tabStop}")
+        (optionalString (space != null) " -spc ${quoteSep space}")
+        (optionalString (nonBreakingSpace != null)
+          " -nbsp ${quoteSep nonBreakingSpace}")
+        (optionalString (lineFeed != null) " -lf ${quoteSep lineFeed}")
       ];
 
     uiOptions = with cfg.config.ui;

tests/modules/programs/kakoune/default.nix

@@ -1 +1,5 @@
-{ kakoune-whitespace-highlighter = ./whitespace-highlighter.nix; }
+{
+  kakoune-whitespace-highlighter = ./whitespace-highlighter.nix;
+  kakoune-whitespace-highlighter-corner-cases =
+    ./whitespace-highlighter-corner-cases.nix;
+}

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

@@ -0,0 +1,25 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  config = {
+    programs.kakoune = {
+      enable = true;
+      config.showWhitespace = {
+        enable = true;
+        lineFeed = ''"'';
+        space = " ";
+        nonBreakingSpace = "' '"; # backwards compat
+        tab = "'";
+        # tabStop = <default>
+      };
+    };
+
+    nmt.script = ''
+      assertFileExists home-files/.config/kak/kakrc
+      assertFileContains home-files/.config/kak/kakrc \
+        "add-highlighter global/ show-whitespaces -tab \"'\" -spc ' ' -nbsp ' ' -lf '\"'"
+    '';
+  };
+}

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

@@ -19,7 +19,7 @@ with lib;
     nmt.script = ''
       assertFileExists home-files/.config/kak/kakrc
       assertFileContains home-files/.config/kak/kakrc \
-        "add-highlighter global/ show-whitespaces -tab 4 -tabpad 5 -spc 2 -nbsp 3 -lf 1"
+        "add-highlighter global/ show-whitespaces -tab '4' -tabpad '5' -spc '2' -nbsp '3' -lf '1'"
     '';
   };
 }