feat(command): add StreamNameMapper to ErrorRecorder (#50)

Author: ar3s3ru

command/error_recorder.go

@@ -37,6 +37,12 @@ type ErrorRecorder struct {
 	// If unspecified, FailedCommandType will be used by default.
 	StreamType string
 
+	// StreamNameMapper maps to a StreamName value based on the command that failed.
+	// This is useful in case you want to use the same Aggregate id the command is targeting.
+	//
+	// If unspecified, the command name will be used instead.
+	StreamNameMapper func(cmd eventually.Command) string
+
 	// EventMapper should return the Domain Event type you defined for these commands.
 	//
 	// NOTE: this is necessary for (de)-serialization purposes while generics are
@@ -53,9 +59,14 @@ func (er ErrorRecorder) streamType() string {
 }
 
 func (er ErrorRecorder) buildStreamID(cmd eventually.Command) eventstore.StreamID {
+	streamName := cmd.Payload.Name()
+	if er.StreamNameMapper != nil {
+		streamName = er.StreamNameMapper(cmd)
+	}
+
 	return eventstore.StreamID{
 		Type: er.streamType(),
-		Name: cmd.Payload.Name(),
+		Name: streamName,
 	}
 }
 

command/error_recorder_test.go

@@ -145,7 +145,8 @@ func TestErrorRecorder(t *testing.T) {
 		eventStore := inmemory.NewEventStore()
 		trackingEventStore := inmemory.NewTrackingEventStore(eventStore)
 
-		expectedStreamType := "mocks-command"
+		const expectedStreamType = "mocks-command"
+
 		expectedErr := errors.New("failed command")
 		expectedCommand := eventually.Command{
 			Payload: mockCommand{message: t.Name()},
@@ -184,4 +185,51 @@ func TestErrorRecorder(t *testing.T) {
 			},
 		}, trackingEventStore.Recorded())
 	})
+
+	t.Run("when handler fails, record event with custom stream name", func(t *testing.T) {
+		eventStore := inmemory.NewEventStore()
+		trackingEventStore := inmemory.NewTrackingEventStore(eventStore)
+
+		expectedStreamType := "mocks-command"
+		expectedErr := errors.New("failed command")
+		expectedCommand := eventually.Command{
+			Payload: mockCommand{message: t.Name()},
+		}
+
+		handler := command.ErrorRecorder{
+			Handler: command.HandlerFunc(func(ctx context.Context, cmd eventually.Command) error {
+				return expectedErr
+			}),
+			Appender:   trackingEventStore,
+			StreamType: expectedStreamType,
+			StreamNameMapper: func(cmd eventually.Command) string {
+				return cmd.Payload.(mockCommand).message
+			},
+			EventMapper: func(err error, cmd eventually.Command) eventually.Payload {
+				return mockCommandHasFailed{
+					err:     err,
+					command: cmd.Payload.(mockCommand),
+				}
+			},
+		}
+
+		err := handler.Handle(context.Background(), expectedCommand)
+
+		assert.Error(t, err)
+		assert.Equal(t, []eventstore.Event{
+			{
+				Version: 1,
+				Stream: eventstore.StreamID{
+					Type: expectedStreamType,
+					Name: expectedCommand.Payload.(mockCommand).message,
+				},
+				Event: eventually.Event{
+					Payload: mockCommandHasFailed{
+						err:     expectedErr,
+						command: expectedCommand.Payload.(mockCommand),
+					},
+				},
+			},
+		}, trackingEventStore.Recorded())
+	})
 }