Paper/Spigot-Server-Patches/0551-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 cbc19202465c128f22933df25661811cc9f99a8f..84e2d402cc749063cd83afb5ed2513d2168944bb 100644
--- a/src/main/java/net/minecraft/server/BlockMinecartDetector.java
+++ b/src/main/java/net/minecraft/server/BlockMinecartDetector.java
@@ -55,6 +55,7 @@ public class BlockMinecartDetector extends BlockMinecartTrackAbstract {
     }
 
     private void a(World world, BlockPosition blockposition, IBlockData iblockdata) {
+        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 18d60b85aa05bf5575ff65b202786f56deff5b51..4ad2e4932dcf60a90027e08ef037e9cca579dfc4 100644
--- a/src/main/java/net/minecraft/server/BlockMinecartTrackAbstract.java
+++ b/src/main/java/net/minecraft/server/BlockMinecartTrackAbstract.java
@@ -41,6 +41,7 @@ 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
             }
 
         }
diff --git a/src/main/java/net/minecraft/server/MinecartTrackLogic.java b/src/main/java/net/minecraft/server/MinecartTrackLogic.java
index 8f9eef8237932d78487e2a6c3c7302e1e233f3fd..f78321d4ff2f633d7291bc44c478068f384612ca 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
     }
 }