Fix LoadingCarts in 1.20.2 and patch-in backwards-compat.

Author: zenfyrdev

CHANGELOG.md

@@ -4,6 +4,7 @@
 * Fix velocityMultiplier not being applied. (By [GeeTransit](https://github.com/GeeTransit))
 * Carts will now stop when the link is broken. (By [GeeTransit](https://github.com/GeeTransit))
 * Ensure train carts don't reverse on sharp curves. (By [GeeTransit](https://github.com/GeeTransit))
+* Updated to 1.20.2.
 * Updated icon and contributors.
 * Loader version is now enforced.
 * Some other minor improvements.

src/main/java/com/github/vini2003/linkart/utility/Lambdas.java

@@ -0,0 +1,30 @@
+package com.github.vini2003.linkart.utility;
+
+import java.lang.invoke.*;
+
+public class Lambdas {
+
+    //TODO maybe use ASM?
+    public static <T> T handle(MethodHandles.Lookup lookup, Class<T> type, MethodHandle h) {
+        CallSite site = supply(() -> LambdaMetafactory.metafactory(lookup, "invoke",
+                MethodType.methodType(type), h.type(), h, h.type()));
+        return supply(() -> (T) site.getTarget().invoke());
+    }
+
+    public static <R, E extends Throwable> R supply(ThrowingSupplier<R, E> supplier) {
+        try {
+            return supplier.get();
+        } catch (Throwable e) {
+            return sneak(e);
+        }
+    }
+
+    public static <E extends Throwable, R> R sneak(Throwable exception) throws E {
+        throw (E) exception;
+    }
+
+    @FunctionalInterface
+    public interface ThrowingSupplier<T, E extends Throwable> {
+        T get() throws E;
+    }
+}

src/main/java/com/github/vini2003/linkart/utility/LoadingCarts.java

@@ -1,5 +1,6 @@
 package com.github.vini2003.linkart.utility;
 
+import net.fabricmc.loader.api.FabricLoader;
 import net.minecraft.entity.vehicle.AbstractMinecartEntity;
 import net.minecraft.nbt.NbtCompound;
 import net.minecraft.nbt.NbtElement;
@@ -10,16 +11,39 @@
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.ChunkPos;
 import net.minecraft.world.PersistentState;
+import net.minecraft.world.PersistentStateManager;
 
+import java.lang.invoke.*;
 import java.util.HashSet;
 import java.util.Set;
+import java.util.function.Function;
+import java.util.function.Supplier;
 
 public class LoadingCarts extends PersistentState {
 
+    private static Function<PersistentStateManager, LoadingCarts> GETTER;
+    static {
+        Supplier<LoadingCarts> supplier = LoadingCarts::new;
+        Function<NbtCompound, LoadingCarts> function = nbt -> new LoadingCarts().readNbt(nbt);
+        try {
+            Type<LoadingCarts> type = new Type<>(supplier, function, null);//thanks, FAPI
+            GETTER = manager -> manager.getOrCreate(type, "linkart_loading_carts");
+        } catch (Throwable e) {
+            String mth = FabricLoader.getInstance().getMappingResolver().mapMethodName("intermediary", "net.minecraft.class_26", "method_17924", "(Ljava/util/function/Function;Ljava/util/function/Supplier;Ljava/lang/String;)Lnet/minecraft/class_18;");
+            MethodHandle h = Lambdas.supply(() -> MethodHandles.lookup().findVirtual(PersistentStateManager.class, mth, MethodType.methodType(PersistentState.class, Function.class, Supplier.class, String.class)));
+
+            //Not pretty, but is faster than reflection and handles.
+            interface Invoker {
+                PersistentState invoke(PersistentStateManager manager, Function<?,?> f, Supplier<?> s, String name);
+            }
+
+            Invoker invoker = Lambdas.handle(MethodHandles.lookup(), Invoker.class, h);
+            GETTER = manager -> (LoadingCarts) invoker.invoke(manager, function, supplier, "linkart_loading_carts");;
+        }
+    }
+
     public static LoadingCarts getOrCreate(ServerWorld world) {
-        return world.getPersistentStateManager().getOrCreate(
-                (nbt) -> new LoadingCarts().readNbt(nbt),
-                LoadingCarts::new, "linkart_loading_carts");
+        return GETTER.apply(world.getPersistentStateManager());
     }
 
     private final Set<BlockPos> chunksToReload = new HashSet<>();