Fix backtrace error

lib/graphql/backtrace/table.rb

@@ -90,7 +90,16 @@ def rows
 
           if ast_node
             field_defn = query.get_field(result.graphql_result_type, ast_node.name)
-            args = query.arguments_for(ast_node, field_defn).to_h
+            args = begin
+              if (cached_args = query.arguments_cache.cached_arguments_for(ast_node, field_defn))
+                cached_args.to_h
+              else
+                EmptyObjects::EMPTY_HASH
+              end
+            rescue StandardError => err
+              "Failed to load arguments, #{err.class}: #{err.message}"
+            end
+
             field_path = field_defn.path
             if ast_node.alias
               field_path += " as #{ast_node.alias}"

lib/graphql/execution/interpreter/arguments_cache.rb

@@ -30,7 +30,10 @@ def fetch(ast_node, argument_owner, parent_object)
               @storage[argument_owner][parent_object][ast_node] = resolved_args
             end
           end
+        end
 
+        def cached_arguments_for(ast_node, argument_owner)
+          @storage[argument_owner][nil][ast_node]
         end
 
         # @yield [Interpreter::Arguments, Lazy<Interpreter::Arguments>] The finally-loaded arguments

spec/graphql/backtrace_spec.rb

@@ -375,4 +375,44 @@ def greeting(name:)
       assert_equal ["name is too short (minimum is 5)"], ValidatorBacktraceSchema.execute("{ greeting(name: \"Tim\") }")["errors"].map { |e| e["message"] }
     end
   end
+
+
+  describe "when prepare fails as in https://github.com/rmosolgo/graphql-ruby/issues/5627" do
+    class BacktracePrepareErrorSchema < GraphQL::Schema
+      class CreateComment < GraphQL::Schema::RelayClassicMutation
+        argument :author_id, String, as: :author, prepare: :prepare_author
+        argument :body,      String
+
+        field :comment_id, String
+
+        def self.prepare_author(id, _ctx)
+          raise "Author #{id} not found"
+        end
+
+        def resolve(author:, body:)
+          { comment_id: "new-comment" }
+        end
+      end
+
+      class Mutation < GraphQL::Schema::Object
+        field :create_comment, mutation: CreateComment
+      end
+
+      use GraphQL::Backtrace
+      mutation Mutation
+    end
+
+    it "works" do
+      skip_with_exec_next
+      assert_raises GraphQL::Backtrace::TracedError do
+        BacktracePrepareErrorSchema.execute <<~GRAPHQL
+          mutation {
+            createComment(input: { authorId: "unknown", body: "hello" }) {
+              commentId
+            }
+          }
+        GRAPHQL
+      end
+    end
+  end
 end