Fix cross-region block access and replaced block checks

worldguard-bukkit/src/main/java/com/sk89q/worldguard/bukkit/cause/Cause.java

@@ -176,11 +176,17 @@ public Entity getFirstNonPlayerEntity() {
         return null;
     }
 
+    /**
+     * Get the first causing block if it is accessible from the current thread.
+     * On Folia, the block may belong to a different region or world.
+     *
+     * @return the block, or null if there is no block or its region is not owned by the current thread
+     */
     @Nullable
     public Block getFirstBlock() {
         for (Object object : causes) {
             if (object instanceof Block b) {
-                return b;
+                return WorldGuardPlugin.inst().isFolia() && !Bukkit.isOwnedByCurrentRegion(b.getLocation()) ? null : b;
             }
         }
 

worldguard-bukkit/src/main/java/com/sk89q/worldguard/bukkit/listener/EventAbstractionListener.java

@@ -246,7 +246,7 @@ public void onBlockPlace(BlockPlaceEvent event) {
         BlockState previousState = event.getBlockReplacedState();
 
         // Some blocks, like tall grass and fire, get replaced
-        if (previousState.getType() != Material.AIR && previousState.getType() != event.getBlockReplacedState().getType()) {
+        if (previousState.getType() != Material.AIR && previousState.getType() != event.getBlockPlaced().getType()) {
             Events.fireToCancel(event, new BreakBlockEvent(event, create(event.getPlayer()), previousState.getLocation(), previousState.getType()));
         }
 

worldguard-bukkit/src/main/java/com/sk89q/worldguard/bukkit/listener/RegionFlagsListener.java

@@ -62,11 +62,9 @@ public void onPlaceBlock(final PlaceBlockEvent event) {
 
         RegionQuery query = WorldGuard.getInstance().getPlatform().getRegionContainer().createQuery();
 
-        Block block;
-        if ((block = event.getCause().getFirstBlock()) != null) {
-            if (Materials.isPistonBlock(block.getType())) {
-                event.filter(testState(query, Flags.PISTONS), false);
-            }
+        Block causeBlock = event.getCause().getFirstBlock();
+        if (causeBlock != null && Materials.isPistonBlock(causeBlock.getType())) {
+            event.filter(testState(query, Flags.PISTONS), false);
         }
 
         if (event.getCause().find(EntityType.SNOW_GOLEM) != null) {
@@ -85,11 +83,9 @@ public void onBreakBlock(final BreakBlockEvent event) {
         WorldConfiguration config = getWorldConfig(event.getWorld());
         RegionQuery query = WorldGuard.getInstance().getPlatform().getRegionContainer().createQuery();
 
-        Block block;
-        if ((block = event.getCause().getFirstBlock()) != null) {
-            if (Materials.isPistonBlock(block.getType())) {
-                event.filter(testState(query, Flags.PISTONS), false);
-            }
+        Block causeBlock = event.getCause().getFirstBlock();
+        if (causeBlock != null && Materials.isPistonBlock(causeBlock.getType())) {
+            event.filter(testState(query, Flags.PISTONS), false);
         }
 
         if (event.getCause().find(EntityType.CREEPER) != null) { // Creeper

worldguard-bukkit/src/main/java/com/sk89q/worldguard/bukkit/listener/RegionProtectionListener.java

@@ -177,9 +177,10 @@ public void onPlaceBlock(final PlaceBlockEvent event) {
 
             /* Flint and steel, fire charge, etc. */
             if (Materials.isFire(type)) {
-                Block block = event.getCause().getFirstBlock();
-                boolean fire = block != null && Materials.isFire(block.getType());
-                boolean lava = block != null && Materials.isLava(block.getType());
+                Block causeBlock = event.getCause().getFirstBlock();
+                Material causeType = causeBlock != null ? causeBlock.getType() : null;
+                boolean fire = causeType != null && Materials.isFire(causeType);
+                boolean lava = causeType != null && Materials.isLava(causeType);
                 List<StateFlag> flags = new ArrayList<>();
                 flags.add(Flags.BLOCK_PLACE);
                 flags.add(Flags.LIGHTER);