lsp: show function signature, use conform.nvim for formatting code.

config/lsp/nvim-metals.nix

@@ -8,12 +8,28 @@
 
   extraPackages = [
     pkgs.metals
+    pkgs.scalafmt
   ];
 
   autoGroups.nvim_metals_group = {
     clear = true;
   };
 
+  extraConfigLua = ''
+    metals_config = require("metals").bare_config()
+    metals_config.init_options.statusBarProvider = "off"
+    metals_config.settings = {
+      showInferredType = true,
+      showImplicitArguments = false,
+      showImplicitConversionsAndClasses = false,
+      metalsBinaryPath = "${pkgs.lib.getExe pkgs.metals}",
+      excludedPackages = { "akka.actor.typed.javadsl", "com.github.swagger.akka.javadsl" },
+      useGlobalExecutable = true,
+      verboseCompilation = true
+    }
+    metals_config.capabilities = require("cmp_nvim_lsp").default_capabilities()
+  '';
+
   autoCmd = [
     {
       event = "FileType";
@@ -21,18 +37,10 @@
       desc = "Initialize nvim-metals";
       callback = helpers.mkRaw ''
         function()
-          metals_config = require("metals").bare_config()
-          metals_config.init_options.statusBarProvider = "off"
-          metals_config.settings = {
-            showInferredType = true,
-            showImplicitArguments = false,
-            showImplicitConversionsAndClasses = false,
-            metalsBinaryPath = "${pkgs.lib.getExe pkgs.metals}",
-            useGlobalExecutable = true
-          }
           require("metals").initialize_or_attach(metals_config)
         end
       '';
+      pattern = [ "scala" "sbt" ];
     }
   ];