Fix Electric Chainsaws Voiding Items

src/main/java/com/nomiceu/nomilabs/mixin/gregtech/ToolEventHandlersMixin.java

@@ -0,0 +1,35 @@
+package com.nomiceu.nomilabs.mixin.gregtech;
+
+import net.minecraft.util.EnumHand;
+import net.minecraftforge.event.entity.player.PlayerDestroyItemEvent;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+import gregtech.common.ToolEventHandlers;
+
+/**
+ * Fix chainsaw breaking replacing currently held item with power unit, regardless of whether it is the chainsaw.
+ */
+@Mixin(value = ToolEventHandlers.class, remap = false)
+public class ToolEventHandlersMixin {
+
+    @Redirect(method = "onPlayerDestroyItem",
+              at = @At(value = "INVOKE",
+                       target = "Lnet/minecraftforge/event/entity/player/PlayerDestroyItemEvent;getHand()Lnet/minecraft/util/EnumHand;",
+                       ordinal = 0),
+              require = 1)
+    private static EnumHand checkForSameStack(PlayerDestroyItemEvent instance) {
+        var hand = instance.getHand();
+        if (hand == null) return null;
+
+        // For the tree felling routine, the player may no longer be holding the chainsaw
+        // Check for exact instance equality, and if not, return null
+        // Returning null leads to the item being added to inventory instead of replacing item in hand
+        if (instance.getEntityPlayer().getHeldItem(hand) != instance.getOriginal())
+            return null;
+
+        return hand;
+    }
+}

src/main/resources/mixins.nomilabs.gregtech.json

@@ -43,6 +43,7 @@
     "SteamBoilerMixin",
     "SteamMetaTileEntityMixin",
     "TileEntityPipeBaseMixin",
+    "ToolEventHandlersMixin",
     "VirtualizedRecipeMapMixin"
   ],
   "client": [