Added transformer for onUsingTick in EntityPlayer

src/main/java/com/mitchej123/hodgepodge/asm/AsmTransformers.java

@@ -51,7 +51,13 @@ public enum AsmTransformers {
             "Removes the logging of GL errors from OptiFine/Shadersmod",
             () -> TweaksConfig.removeOptifineGLErrors,
             Side.CLIENT,
-            "com.mitchej123.hodgepodge.asm.transformers.optifine.GLErrorLoggingTransformer");
+            "com.mitchej123.hodgepodge.asm.transformers.optifine.GLErrorLoggingTransformer"),
+    FIX_ON_USING_TICK(
+            "Changes EntityPlayer.onUpdate to use ItemStack.areItemStacksEqual instead of ==.",
+            () -> FixesConfig.fixOnUsingTick,
+            Side.BOTH,
+            "com.mitchej123.hodgepodge.asm.transformers.mc.EntityPlayerTransformer"
+            );
     // spotless:on
 
     private final Supplier<Boolean> applyIf;

src/main/java/com/mitchej123/hodgepodge/asm/transformers/mc/EntityPlayerTransformer.java

@@ -0,0 +1,105 @@
+package com.mitchej123.hodgepodge.asm.transformers.mc;
+
+import net.minecraft.launchwrapper.IClassTransformer;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.tree.ClassNode;
+import org.objectweb.asm.tree.FieldInsnNode;
+import org.objectweb.asm.tree.JumpInsnNode;
+import org.objectweb.asm.tree.MethodInsnNode;
+
+public class EntityPlayerTransformer implements IClassTransformer {
+
+    private static final Logger LOGGER = LogManager.getLogger("EntityPlayerTransformer");
+
+    @Override
+    public byte[] transform(String name, String transformedName, byte[] basicClass) {
+        if (basicClass == null) return null;
+
+        if (NameContext.Obf.entityPlayer.equals(name)) {
+            final ClassReader cr = new ClassReader(basicClass);
+            final ClassNode cn = new ClassNode();
+            cr.accept(cn, 0);
+            transformClassNode(NameContext.Obf, cn);
+            ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
+            cn.accept(cw);
+
+            LOGGER.info("Transformed {}", name);
+            return cw.toByteArray();
+        }
+
+        if (NameContext.Deobf.entityPlayer.equals(name)) {
+            final ClassReader cr = new ClassReader(basicClass);
+            final ClassNode cn = new ClassNode();
+            cr.accept(cn, 0);
+            transformClassNode(NameContext.Deobf, cn);
+            ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
+            cn.accept(cw);
+
+            LOGGER.info("Transformed {}", name);
+            return cw.toByteArray();
+        }
+
+        return basicClass;
+    }
+
+    public void transformClassNode(NameContext names, ClassNode cn) {
+        LOGGER.info("Found EntityPlayer (class = {}, name context = {})", names.entityPlayer, names.name());
+
+        for (var method : cn.methods) {
+            if (method.name.equals(names.onUpdate)) {
+                LOGGER.info("Found EntityPlayer.onUpdate ({})", names.onUpdate);
+
+                var cursor = method.instructions.getFirst();
+
+                while (cursor != null) {
+                    if (cursor instanceof FieldInsnNode field && field.getOpcode() == Opcodes.GETFIELD
+                            && field.name.equals(names.itemInUse)) {
+                        if (cursor.getNext() instanceof JumpInsnNode jump && jump.getOpcode() == Opcodes.IF_ACMPNE) {
+                            LOGGER.info("Found injection point");
+
+                            method.instructions.insertBefore(
+                                    jump,
+                                    new MethodInsnNode(
+                                            Opcodes.INVOKESTATIC,
+                                            names.itemStack,
+                                            names.areItemStacksEqual,
+                                            String.format("(L%s;L%s;)Z", names.itemStack, names.itemStack),
+                                            false));
+
+                            ((JumpInsnNode) jump).setOpcode(Opcodes.IFEQ);
+                            return;
+                        }
+                    }
+
+                    cursor = cursor.getNext();
+                }
+
+                LOGGER.warn("Could not find injection point.");
+            }
+        }
+    }
+
+    private static enum NameContext {
+
+        Deobf("net.minecraft.entity.player.EntityPlayer", "onUpdate", "net/minecraft/item/ItemStack",
+                "areItemStacksEqual", "itemInUse"),
+        Obf("yz", "h", "add", "b", "f");
+
+        public final String entityPlayer, onUpdate, itemStack, areItemStacksEqual, itemInUse;
+
+        private NameContext(String entityPlayer, String onUpdate, String itemStack, String areItemStacksEqual,
+                String itemInUse) {
+            this.entityPlayer = entityPlayer;
+            this.onUpdate = onUpdate;
+            this.itemStack = itemStack;
+            this.areItemStacksEqual = areItemStacksEqual;
+            this.itemInUse = itemInUse;
+        }
+    }
+
+}

src/main/java/com/mitchej123/hodgepodge/config/FixesConfig.java

@@ -352,6 +352,11 @@ public class FixesConfig {
     @Config.RequiresMcRestart
     public static boolean fixCaseCommands;
 
+    @Config.Comment("Fix onUsingTick not getting called on the server")
+    @Config.DefaultBoolean(true)
+    @Config.RequiresMcRestart
+    public static boolean fixOnUsingTick;
+
     // affecting multiple mods
 
     @Config.Comment("Remove old/stale/outdated update checks.")