fix crash when cwd is nil

Author: lukaszsamson

apps/language_server/lib/language_server/diagnostics.ex

@@ -270,7 +270,7 @@ defmodule ElixirLS.LanguageServer.Diagnostics do
     }
   end
 
-  def exception_to_diagnostic(error, path \\ MixfileHelpers.mix_exs()) do
+  def exception_to_diagnostic(error, path) do
     msg =
       case error do
         {:shutdown, 1} ->
@@ -282,7 +282,7 @@ defmodule ElixirLS.LanguageServer.Diagnostics do
 
     %Mix.Task.Compiler.Diagnostic{
       compiler_name: "ElixirLS",
-      file: Path.absname(path),
+      file: path,
       # 0 means unknown
       position: 0,
       message: msg,

apps/language_server/lib/language_server/server.ex

@@ -311,12 +311,6 @@ defmodule ElixirLS.LanguageServer.Server do
       ) do
     state = %{state | build_running?: false}
 
-    state =
-      case reason do
-        :normal -> state
-        _ -> handle_build_result(:error, [Diagnostics.exception_to_diagnostic(reason)], state)
-      end
-
     # in case the build was interrupted make sure that cwd is reset to project dir
     case File.cd(state.project_dir) do
       :ok ->
@@ -330,6 +324,16 @@ defmodule ElixirLS.LanguageServer.Server do
         JsonRpc.show_message(:error, message)
     end
 
+    state =
+      case reason do
+        :normal ->
+          state
+
+        _ ->
+          path = Path.join(state.project_dir, MixfileHelpers.mix_exs())
+          handle_build_result(:error, [Diagnostics.exception_to_diagnostic(reason, path)], state)
+      end
+
     if reason == :normal do
       WorkspaceSymbols.notify_build_complete()
     end