nixos/fcitx5: add the setting of RIME_DATA_DIR and options for rime-data

nixos/modules/i18n/input-method/fcitx5.nix

@@ -5,7 +5,9 @@ with lib;
 let
   im = config.i18n.inputMethod;
   cfg = im.fcitx5;
-  fcitx5Package = pkgs.fcitx5-with-addons.override { inherit (cfg) addons; };
+  addons = cfg.addons ++ optional cfg.enableRimeData pkgs.rime-data;
+  fcitx5Package = pkgs.fcitx5-with-addons.override { inherit addons; };
+  whetherRimeDataDir = any (p: p.pname == "fcitx5-rime") cfg.addons;
 in {
   options = {
     i18n.inputMethod.fcitx5 = {
@@ -17,16 +19,29 @@ in {
           Enabled Fcitx5 addons.
         '';
       };
+
+      enableRimeData = mkEnableOption "default rime-data with fcitx5-rime";
     };
   };
 
   config = mkIf (im.enabled == "fcitx5") {
     i18n.inputMethod.package = fcitx5Package;
 
-    environment.variables = {
-      GTK_IM_MODULE = "fcitx";
-      QT_IM_MODULE = "fcitx";
-      XMODIFIERS = "@im=fcitx";
-    };
+    environment = mkMerge [{
+      variables = {
+        GTK_IM_MODULE = "fcitx";
+        QT_IM_MODULE = "fcitx";
+        XMODIFIERS = "@im=fcitx";
+      };
+    }
+    (mkIf whetherRimeDataDir {
+      pathsToLink = [
+        "/share/rime-data"
+      ];
+
+      variables =  {
+        NIX_RIME_DATA_DIR = "/run/current-system/sw/share/rime-data";
+      };
+    })];
   };
 }