fix(elixir): format inside runtime

This ensures that formatter plugins can be utilized.

lib/next_ls.ex

@@ -97,9 +97,11 @@ defmodule NextLS do
   def handle_request(%TextDocumentFormatting{params: %{text_document: %{uri: uri}}}, lsp) do
     document = lsp.assigns.documents[uri]
 
-    working_dir = URI.parse(lsp.assigns.root_uri).path
-    {opts, _} = Code.eval_file(".formatter.exs", working_dir)
-    new_document = Code.format_string!(Enum.join(document, "\n"), opts) |> IO.iodata_to_binary()
+    {formatter, _} = Runtime.call(lsp.assigns.runtime, {Mix.Tasks.Format, :formatter_for_file, [".formatter.exs"]})
+
+    new_document =
+      Runtime.call(lsp.assigns.runtime, {Kernel, :apply, [formatter, [Enum.join(document, "\n")]]})
+      |> IO.iodata_to_binary()
 
     {:reply,
      [

test/next_ls_test.exs

@@ -190,6 +190,9 @@ defmodule NextLSTest do
                params: %{}
              })
 
+    assert_notification "window/logMessage",
+                        %{"message" => "[NextLS] Runtime ready..."}
+
     notify client, %{
       method: "textDocument/didOpen",
       jsonrpc: "2.0",
@@ -226,15 +229,13 @@ defmodule NextLSTest do
       }
     }
 
-    new_text =
-      """
-      defmodule Foo.Bar do
-        def run() do
-          :ok
-        end
+    new_text = """
+    defmodule Foo.Bar do
+      def run() do
+        :ok
       end
-      """
-      |> String.trim()
+    end
+    """
 
     assert_result(
       2,