fix: preserve respond_with_error payloads

lib/leopard/message_wrapper.rb

@@ -31,11 +31,11 @@ def respond(payload)
         raw.respond(serialize(payload))
       end
 
-      # @param err [String, Exception] The error message or exception to respond with.
+      # @param err [Object] The error payload to respond with.
       #
       # @return [void]
-      def respond_with_error(err)
-        raw.respond_with_error(err.to_s)
+      def respond_with_error(err, &)
+        raw.respond_with_error(err, &)
       end
 
       private

lib/leopard/nats_api_server.rb

@@ -313,7 +313,7 @@ def handle_message(raw_msg, handler)
           process_result(wrapper, result)
         rescue StandardError => e
           logger.error 'Error processing message: ', e
-          wrapper.respond_with_error(e.message)
+          wrapper.respond_with_error(e)
         end
 
         # Processes the result of the handler execution.

test/lib/message_wrapper.rb

@@ -4,7 +4,7 @@
 require 'leopard/message_wrapper'
 
 class FakeMsg
-  attr_reader :data, :responded_payload, :error_args
+  attr_reader :data, :responded_payload, :error_args, :error_block_called_with
   attr_accessor :header
 
   def initialize(data, header = {})
@@ -18,6 +18,11 @@ def respond(payload)
 
   def respond_with_error(err)
     @error_args = [err]
+    return unless block_given?
+
+    yielded_error = {}
+    yield yielded_error
+    @error_block_called_with = yielded_error
   end
 end
 
@@ -63,10 +68,23 @@ def respond_with_error(err)
     assert_equal ['fail'], msg.error_args
   end
 
-  it 'coerces exception objects to strings when responding with error' do
+  it 'passes exception objects through when responding with error' do
     err = StandardError.new('broken')
     wrapper.respond_with_error(err)
 
-    assert_equal ['broken'], msg.error_args
+    assert_equal [err], msg.error_args
+  end
+
+  it 'passes hash payloads through when responding with error' do
+    err = { 'description' => 'broken', 'code' => 422 }
+    wrapper.respond_with_error(err)
+
+    assert_equal [err], msg.error_args
+  end
+
+  it 'forwards blocks when responding with error' do
+    wrapper.respond_with_error(code: 422) { |error| error[:code] = 422 }
+
+    assert_equal({ code: 422 }, msg.error_block_called_with)
   end
 end

test/lib/nats_api_server.rb

@@ -139,12 +139,15 @@ def call(wrapper)
 
   it 'responds with error when handler raises' do
     raw_msg = Object.new
-    wrapper = Minitest::Mock.new
-    wrapper.expect(:respond_with_error, nil, ['boom'])
+    err = nil
+    wrapper = Object.new
+    wrapper.define_singleton_method(:respond_with_error) { |raised| err = raised }
     Rubyists::Leopard::MessageWrapper.stub(:new, wrapper) do
       @instance.send(:handle_message, raw_msg, proc { raise 'boom' })
     end
-    wrapper.verify
+
+    assert_instance_of RuntimeError, err
+    assert_equal 'boom', err.message
   end
 
   it 'responds when processing Success result' do
@@ -162,4 +165,13 @@ def call(wrapper)
     @instance.send(:process_result, wrapper, result)
     wrapper.verify
   end
+
+  it 'passes hash failures through unchanged' do
+    err = { code: 422, description: 'invalid' }
+    wrapper = Minitest::Mock.new
+    wrapper.expect(:respond_with_error, nil, [err])
+    result = Rubyists::Leopard::NatsApiServer::Failure.new(err)
+    @instance.send(:process_result, wrapper, result)
+    wrapper.verify
+  end
 end