Throw error on missing clanModule description or if description too long. Add xfce description.

clanModules/xfce/README.md

@@ -1 +1,2 @@
+A lightweight desktop manager
 ---

clanModules/zt-tcp-relay/README.md

@@ -1 +1,2 @@
+Enable ZeroTier VPN over TCP for networks where UDP is blocked.
 ---

lib/default.nix

@@ -6,6 +6,6 @@
 }:
 {
   jsonschema = import ./jsonschema { inherit lib; };
-  modules = import ./description.nix { inherit clan-core; };
+  modules = import ./description.nix { inherit clan-core lib; };
   buildClan = import ./build-clan { inherit clan-core lib nixpkgs; };
 }

lib/description.nix

@@ -1,4 +1,4 @@
-{ clan-core, ... }:
+{ lib, clan-core, ... }:
 
 rec {
   getReadme =
@@ -17,10 +17,17 @@ rec {
     modulename:
     let
       content = (getReadme modulename);
-      parts = builtins.split "---" content;
+      parts = lib.splitString "---" content;
+      description = builtins.head parts;
+      number_of_newlines = builtins.length (lib.splitString "\n" description);
     in
-    if (builtins.length parts) > 0 then
-      builtins.head parts
+    if (builtins.length parts) > 1 then
+      if number_of_newlines > 4 then
+        throw "Short description in README.md for module ${modulename} is too long. Max 3 newlines."
+      else if number_of_newlines <= 1 then
+        throw "Missing short description in README.md for module ${modulename}."
+      else
+        description
     else
       throw "Short description delimiter `---` not found in README.md for module ${modulename}";
 }