From 7cebe692e70df46a8b2d95a0b10189a9497c83e3 Mon Sep 17 00:00:00 2001
From: Shadowfacts <me@shadowfacts.net>
Date: Mon, 11 Jun 2018 17:21:43 -0400
Subject: [PATCH] Only unregister static/register object event handlers unless
 appropriate handler methods are detected

---
 .../ForgelinAutomaticEventSubscriber.kt       | 28 ++++++++++++++++---
 .../forgelin/AutomaticKtSubscriberTest.kt     |  7 +++++
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/src/main/kotlin/net/shadowfacts/forgelin/ForgelinAutomaticEventSubscriber.kt b/src/main/kotlin/net/shadowfacts/forgelin/ForgelinAutomaticEventSubscriber.kt
index 645a9d4..e2e60c3 100644
--- a/src/main/kotlin/net/shadowfacts/forgelin/ForgelinAutomaticEventSubscriber.kt
+++ b/src/main/kotlin/net/shadowfacts/forgelin/ForgelinAutomaticEventSubscriber.kt
@@ -8,8 +8,10 @@ import net.minecraftforge.fml.common.ModContainer
 import net.minecraftforge.fml.common.discovery.ASMDataTable
 import net.minecraftforge.fml.common.discovery.ASMDataTable.ASMData
 import net.minecraftforge.fml.common.discovery.asm.ModAnnotation.EnumHolder
+import net.minecraftforge.fml.common.eventhandler.SubscribeEvent
 import net.minecraftforge.fml.relauncher.Side
 import org.apache.logging.log4j.LogManager
+import java.lang.reflect.Modifier
 import java.util.EnumSet
 import kotlin.reflect.full.companionObjectInstance
 
@@ -45,17 +47,35 @@ object ForgelinAutomaticEventSubscriber {
 
                 val subscriberClass = Class.forName(subscriber.className, false, loader) ?: continue
                 val kotlinClass = subscriberClass.kotlin
-                val subscriberInstance = kotlinClass.objectInstance ?: kotlinClass.companionObjectInstance ?: continue
+                val objectInstance = kotlinClass.objectInstance ?: kotlinClass.companionObjectInstance ?: continue
 
-                MinecraftForge.EVENT_BUS.unregister(subscriberClass)
-                MinecraftForge.EVENT_BUS.register(subscriberInstance)
-                LOGGER.debug("Registered @EventBusSubscriber object {}", subscriber.className)
+                if (!hasStaticEventHandlers(subscriberClass)) {
+                    MinecraftForge.EVENT_BUS.unregister(subscriberClass)
+                    LOGGER.debug("Unregistered static @EventBusSubscriber class {}", subscriber.className)
+                }
+                if (hasObjectEventHandlers(objectInstance)) {
+                    MinecraftForge.EVENT_BUS.register(objectInstance)
+                    LOGGER.debug("Registered @EventBusSubscriber object instance {}", subscriber.className)
+                }
             } catch (e: Throwable) {
                 LOGGER.error("An error occurred trying to load an @EventBusSubscriber object {} for modid {}", mod.modId, e)
+                throw LoaderException(e)
             }
         }
     }
 
+    private fun hasObjectEventHandlers(objectInstance: Any): Boolean {
+        return objectInstance.javaClass.methods.any {
+            !Modifier.isStatic(it.modifiers) && it.isAnnotationPresent(SubscribeEvent::class.java)
+        }
+    }
+
+    private fun hasStaticEventHandlers(clazz: Class<*>): Boolean {
+        return clazz.methods.any {
+            Modifier.isStatic(it.modifiers) && it.isAnnotationPresent(SubscribeEvent::class.java)
+        }
+    }
+
     private fun parseModId(containedMods: MutableSet<ASMData>, subscriber: ASMData): String? {
         val parsedModId: String? = subscriber.annotationInfo["modid"] as? String
         if (parsedModId.isNullOrEmpty()) {
diff --git a/src/test/kotlin/net/shadowfacts/forgelin/AutomaticKtSubscriberTest.kt b/src/test/kotlin/net/shadowfacts/forgelin/AutomaticKtSubscriberTest.kt
index 6b7c308..e98cb51 100644
--- a/src/test/kotlin/net/shadowfacts/forgelin/AutomaticKtSubscriberTest.kt
+++ b/src/test/kotlin/net/shadowfacts/forgelin/AutomaticKtSubscriberTest.kt
@@ -1,5 +1,6 @@
 package net.shadowfacts.forgelin
 
+import net.minecraftforge.event.entity.player.PlayerInteractEvent
 import net.minecraftforge.event.entity.player.PlayerInteractEvent.RightClickBlock
 import net.minecraftforge.fml.common.Mod
 import net.minecraftforge.fml.common.Mod.EventBusSubscriber
@@ -15,5 +16,11 @@ object AutomaticKtSubscriberTest {
         fun onRightClickBlock(event: RightClickBlock) {
             println("Automatic KT subscriber: Right click ${event.pos}")
         }
+
+        @JvmStatic
+        @SubscribeEvent
+        fun onRightClickItem(event: PlayerInteractEvent.RightClickItem) {
+            println("Right click item")
+        }
     }
 }