Prevent relative require completion for unsaved files

lib/ruby_lsp/listeners/completion.rb

@@ -445,11 +445,14 @@ def complete_require_relative(node)
         return unless arguments_node
 
         path_node_to_complete = arguments_node.arguments.first
-
         return unless path_node_to_complete.is_a?(Prism::StringNode)
 
-        origin_dir = Pathname.new(@uri.to_standardized_path).dirname
+        # If the file is unsaved (e.g.: untitled:Untitled-1), we can't provide relative completion as we don't know
+        # where the user intends to save it
+        full_path = @uri.to_standardized_path
+        return unless full_path
 
+        origin_dir = Pathname.new(full_path).dirname
         content = path_node_to_complete.content
         # if the path is not a directory, glob all possible next characters
         # for example ../somethi| (where | is the cursor position)

test/requests/completion_test.rb

@@ -1761,6 +1761,25 @@ def baz
     end
   end
 
+  def test_require_relative_returns_empty_result_for_unsaved_files
+    prefix = "support/"
+    source = <<~RUBY
+      require_relative "#{prefix}"
+    RUBY
+    end_char = source.rindex('"') #: as !nil
+
+    with_server(source, URI("untitled:Untitled-1")) do |server, uri|
+      with_file_structure(server) do
+        server.process_message(id: 1, method: "textDocument/completion", params: {
+          textDocument: { uri: uri },
+          position: { line: 0, character: end_char },
+        })
+
+        assert_empty(server.pop_response.response)
+      end
+    end
+  end
+
   private
 
   def with_file_structure(server, &block)