From 8a30493c52cee87cf7e3f0f12c9ddbd2bfafced3 Mon Sep 17 00:00:00 2001
From: kske <kai@kske.dev>
Date: Fri, 19 Feb 2021 11:34:58 +0100
Subject: [PATCH] Warn about unused event handler return values

If an event handler has a non-void return type, a warning is issued as
the event bus cannot use the returned value.

In rare cases this might be justified as the event handler could be
invoked directly.
---
 .../src/main/java/dev/kske/eventbus/proc/EventProcessor.java  | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/event-bus-proc/src/main/java/dev/kske/eventbus/proc/EventProcessor.java b/event-bus-proc/src/main/java/dev/kske/eventbus/proc/EventProcessor.java
index 9d9122c..fed6f1c 100644
--- a/event-bus-proc/src/main/java/dev/kske/eventbus/proc/EventProcessor.java
+++ b/event-bus-proc/src/main/java/dev/kske/eventbus/proc/EventProcessor.java
@@ -63,6 +63,10 @@ public class EventProcessor extends AbstractProcessor {
 			else
 				pass = true;
 
+			// Warn the user about unused return values
+			if (useParameter && eventHandler.getReturnType().getKind() != TypeKind.VOID)
+					warning(eventHandler, "Unused return value");
+
 			// Abort checking if the handler signature is incorrect
 			if (!pass)
 				continue;