Paper/Spigot-Server-Patches/0539-Fix-some-rails-connecting-improperly.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <spottedleaf@spottedleaf.dev>
Date: Fri, 24 Jul 2020 15:56:05 -0700
Subject: [PATCH] Fix some rails connecting improperly


diff --git a/src/main/java/net/minecraft/server/BlockMinecartDetector.java b/src/main/java/net/minecraft/server/BlockMinecartDetector.java
index 9681e08edf34f17806819115336874b574b880bc..77fde30769860828b6f16eefb186962c140beaae 100644
--- a/src/main/java/net/minecraft/server/BlockMinecartDetector.java
+++ b/src/main/java/net/minecraft/server/BlockMinecartDetector.java
@@ -51,6 +51,7 @@ public class BlockMinecartDetector extends BlockMinecartTrackAbstract {
 
     private void a(World world, BlockPosition blockposition, IBlockData iblockdata) {
         if (this.canPlace(iblockdata, world, blockposition)) {
+            if (iblockdata.getBlock() != this) { return; } // Paper - not our block, don't do anything
             boolean flag = (Boolean) iblockdata.get(BlockMinecartDetector.POWERED);
             boolean flag1 = false;
             List<EntityMinecartAbstract> list = this.a(world, blockposition, EntityMinecartAbstract.class, (Predicate) null);
diff --git a/src/main/java/net/minecraft/server/BlockMinecartTrackAbstract.java b/src/main/java/net/minecraft/server/BlockMinecartTrackAbstract.java
index 5609eeec9a7991167b57b724fa3279d3e8bf6b94..0de3fa45487e996b79d1031c9ee4b0728cfe1bcf 100644
--- a/src/main/java/net/minecraft/server/BlockMinecartTrackAbstract.java
+++ b/src/main/java/net/minecraft/server/BlockMinecartTrackAbstract.java
@@ -46,6 +46,7 @@ public abstract class BlockMinecartTrackAbstract extends Block {
         iblockdata = this.a(world, blockposition, iblockdata, true);
         if (this.c) {
             iblockdata.doPhysics(world, blockposition, this, blockposition, flag);
+            iblockdata = world.getType(blockposition); // Paper - don't desync, update again
         }
 
         return iblockdata;
diff --git a/src/main/java/net/minecraft/server/MinecartTrackLogic.java b/src/main/java/net/minecraft/server/MinecartTrackLogic.java
index 10bc2165159514d484e73a3acd08ca5929be72f2..e0be3a425aae51e1aced8eb6d8a5e84fc9315e3a 100644
--- a/src/main/java/net/minecraft/server/MinecartTrackLogic.java
+++ b/src/main/java/net/minecraft/server/MinecartTrackLogic.java
@@ -7,13 +7,19 @@ import javax.annotation.Nullable;
 
 public class MinecartTrackLogic {
 
-    private final World a;
-    private final BlockPosition b;
+    private final World a; public final World getWorld() { return this.a; } // Paper - OBFHELPER
+    private final BlockPosition b; public final BlockPosition getPos() { return this.b; } // Paper - OBFHELPER
     private final BlockMinecartTrackAbstract c;
-    private IBlockData d;
+    private IBlockData d; public final IBlockData getRailState() { return this.d; } // Paper - OBFHELPER
     private final boolean e;
     private final List<BlockPosition> f = Lists.newArrayList();
 
+    // Paper start - prevent desync
+    public boolean isValid() {
+        return this.getWorld().getType(this.getPos()).getBlock() == this.getRailState().getBlock();
+    }
+    // Paper end - prevent desync
+
     public MinecartTrackLogic(World world, BlockPosition blockposition, IBlockData iblockdata) {
         this.a = world;
         this.b = blockposition;
@@ -148,6 +154,11 @@ public class MinecartTrackLogic {
     }
 
     private void c(MinecartTrackLogic minecarttracklogic) {
+        // Paper start - prevent desync
+        if (!this.isValid() || !minecarttracklogic.isValid()) {
+            return;
+        }
+        // Paper end - prevent desync
         this.f.add(minecarttracklogic.b);
         BlockPosition blockposition = this.b.north();
         BlockPosition blockposition1 = this.b.south();
@@ -342,11 +353,16 @@ public class MinecartTrackLogic {
         this.d = (IBlockData) this.d.set(this.c.d(), blockpropertytrackposition1);
         if (flag1 || this.a.getType(this.b) != this.d) {
             this.a.setTypeAndData(this.b, this.d, 3);
+            // Paper start - prevent desync
+            if (!this.isValid()) {
+                return this;
+            }
+            // Paper end - prevent desync
 
             for (int i = 0; i < this.f.size(); ++i) {
                 MinecartTrackLogic minecarttracklogic = this.b((BlockPosition) this.f.get(i));
 
-                if (minecarttracklogic != null) {
+                if (minecarttracklogic != null && minecarttracklogic.isValid()) { // Paper - prevent desync
                     minecarttracklogic.d();
                     if (minecarttracklogic.b(this)) {
                         minecarttracklogic.c(this);
@@ -359,6 +375,6 @@ public class MinecartTrackLogic {
     }
 
     public IBlockData c() {
-        return this.d;
+        return this.getWorld().getType(this.getPos()); // Paper - prevent desync
     }
 }