Paper/Remapped-Spigot-Server-Patches/0536-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/world/level/block/BaseRailBlock.java b/src/main/java/net/minecraft/world/level/block/BaseRailBlock.java
index 1a44c8b41928a83a22b53d1b6f45ce39b4caf2b2..7cef6d1fc2045c62d4e96a0fd0a311d089cb1406 100644
--- a/src/main/java/net/minecraft/world/level/block/BaseRailBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/BaseRailBlock.java
@@ -62,6 +62,7 @@ public abstract class BaseRailBlock extends Block {
         state = this.updateDir(world, pos, state, true);
         if (this.isStraight) {
             state.neighborChanged(world, pos, this, pos, notify);
+            state = world.getBlockState(pos); // Paper - don't desync, update again
         }
 
         return state;
diff --git a/src/main/java/net/minecraft/world/level/block/DetectorRailBlock.java b/src/main/java/net/minecraft/world/level/block/DetectorRailBlock.java
index 0ab1e15d8575c3e90a10b80b94030e15a01faac9..1854809e045300e84a713dc7c3a8264f53ec6c0f 100644
--- a/src/main/java/net/minecraft/world/level/block/DetectorRailBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/DetectorRailBlock.java
@@ -70,6 +70,7 @@ public class DetectorRailBlock extends BaseRailBlock {
 
     private void checkPressed(Level world, BlockPos pos, BlockState state) {
         if (this.canSurvive(state, world, pos)) {
+            if (state.getBlock() != this) { return; } // Paper - not our block, don't do anything
             boolean flag = (Boolean) state.getValue(DetectorRailBlock.POWERED);
             boolean flag1 = false;
             List<AbstractMinecart> list = this.getInteractingMinecartOfType(world, pos, AbstractMinecart.class, (Predicate) null);
diff --git a/src/main/java/net/minecraft/world/level/block/RailState.java b/src/main/java/net/minecraft/world/level/block/RailState.java
index 0d824ab98dcdd6ea9dac025c37970fb4ec464131..4c17bec369fb19f47760e30b391b2128cee6b276 100644
--- a/src/main/java/net/minecraft/world/level/block/RailState.java
+++ b/src/main/java/net/minecraft/world/level/block/RailState.java
@@ -12,13 +12,19 @@ import net.minecraft.world.level.block.state.properties.RailShape;
 
 public class RailState {
 
-    private final Level level;
-    private final BlockPos pos;
+    private final Level level; public final Level getWorld() { return this.level; } // Paper - OBFHELPER
+    private final BlockPos pos; public final BlockPos getPos() { return this.pos; } // Paper - OBFHELPER
     private final BaseRailBlock block;
-    private BlockState state;
+    private BlockState state; public final BlockState getRailState() { return this.state; } // Paper - OBFHELPER
     private final boolean isStraight;
     private final List<BlockPos> connections = Lists.newArrayList();
 
+    // Paper start - prevent desync
+    public boolean isValid() {
+        return this.getWorld().getBlockState(this.getPos()).getBlock() == this.getRailState().getBlock();
+    }
+    // Paper end - prevent desync
+
     public RailState(Level world, BlockPos pos, BlockState state) {
         this.level = world;
         this.pos = pos;
@@ -153,6 +159,11 @@ public class RailState {
     }
 
     private void connectTo(RailState placementHelper) {
+        // Paper start - prevent desync
+        if (!this.isValid() || !placementHelper.isValid()) {
+            return;
+        }
+        // Paper end - prevent desync
         this.connections.add(placementHelper.pos);
         BlockPos blockposition = this.pos.north();
         BlockPos blockposition1 = this.pos.south();
@@ -347,11 +358,16 @@ public class RailState {
         this.state = (BlockState) this.state.setValue(this.block.getShapeProperty(), blockpropertytrackposition1);
         if (forceUpdate || this.level.getBlockState(this.pos) != this.state) {
             this.level.setBlock(this.pos, this.state, 3);
+            // Paper start - prevent desync
+            if (!this.isValid()) {
+                return this;
+            }
+            // Paper end - prevent desync
 
             for (int i = 0; i < this.connections.size(); ++i) {
                 RailState minecarttracklogic = this.getRail((BlockPos) this.connections.get(i));
 
-                if (minecarttracklogic != null) {
+                if (minecarttracklogic != null && minecarttracklogic.isValid()) { // Paper - prevent desync
                     minecarttracklogic.removeSoftConnections();
                     if (minecarttracklogic.canConnectTo(this)) {
                         minecarttracklogic.connectTo(this);
@@ -364,6 +380,6 @@ public class RailState {
     }
 
     public BlockState getState() {
-        return this.state;
+        return this.getWorld().getBlockState(this.getPos()); // Paper - prevent desync
     }
 }