modules/lsp/servers/vls: do not add filetype extension if not enabled

tests/test-sources/plugins/lsp/language-servers/vls.nix

@@ -0,0 +1,29 @@
+{
+  default = {
+    plugins.lsp = {
+      enable = true;
+      servers.vls.enable = true;
+    };
+
+    extraConfigLuaPost = ''
+      -- V files are recognized by default
+      assert(vim.filetype.match({ filename = "test.v" }) == "vlang", "V filetype is not recognized")
+    '';
+  };
+
+  extra-options = {
+    plugins.lsp = {
+      enable = true;
+
+      servers.vls = {
+        enable = true;
+        autoSetFiletype = true;
+      };
+    };
+
+    extraConfigLuaPost = ''
+      -- autoSetFiletype
+      assert(vim.filetype.match({ filename = "test.v" }) == "vlang", "V filetype is not recognized")
+    '';
+  };
+}