fix(expert): save new configuration after workspace/didChangeConfiguration (#282)

State handler of workspace/didChangeConfiguration message was always
returning old configuration, so the changes to dialyzer support were not
preserved.

This is maybe not super important, as the dialyzer config does not seem
to be used anywhere, but it gets the general `didChangeConfiguration`
flow right for the future - and I would like to add `projectDir` change
handled by `didChangeConfiguration`, as this is default way to tweak the
setting per-project in Emacs.

Author: katafrakt

apps/expert/lib/expert/state.ex

@@ -91,8 +91,6 @@ defmodule Expert.State do
         GenLSP.request(Expert.get_lsp(), request)
         {:ok, %__MODULE__{state | configuration: config}}
     end
-
-    {:ok, state}
   end
 
   def apply(%__MODULE__{} = state, %Notifications.WorkspaceDidChangeWorkspaceFolders{

apps/expert/test/expert_test.exs

@@ -7,6 +7,32 @@ defmodule Expert.ExpertTest do
 
   import Expert.Test.Protocol.TransportSupport
 
+  describe "workspace/didChangeConfiguration" do
+    test "updates configuration when settings change" do
+      with_patched_transport()
+
+      patch(Expert.Dialyzer, :check_support, :ok)
+
+      project = Fixtures.project()
+      lsp = initialize_lsp(project)
+
+      # dialyzer_enabled? defaults to false
+      assert GenLSP.Assigns.get(lsp.assigns).state.configuration.dialyzer_enabled? == false
+
+      did_change_config = %GenLSP.Notifications.WorkspaceDidChangeConfiguration{
+        jsonrpc: "2.0",
+        method: "workspace/didChangeConfiguration",
+        params: %GenLSP.Structures.DidChangeConfigurationParams{
+          settings: %{"dialyzerEnabled" => true}
+        }
+      }
+
+      assert {:noreply, updated_lsp} = Expert.handle_notification(did_change_config, lsp)
+
+      assert GenLSP.Assigns.get(updated_lsp.assigns).state.configuration.dialyzer_enabled? == true
+    end
+  end
+
   test "sends an error message on engine initialization error" do
     with_patched_transport()