Paper/paper-server/patches/sources/net/minecraft/world/item/BlockItem.java.patch

--- a/net/minecraft/world/item/BlockItem.java
+++ b/net/minecraft/world/item/BlockItem.java
@@ -57,6 +_,14 @@
                 return InteractionResult.FAIL;
             } else {
                 BlockState placementState = this.getPlacementState(blockPlaceContext);
+                // CraftBukkit start - special case for handling block placement with water lilies and snow buckets
+                org.bukkit.block.BlockState bukkitState = null;
+                if (this instanceof PlaceOnWaterBlockItem || this instanceof SolidBucketItem) {
+                    bukkitState = org.bukkit.craftbukkit.block.CraftBlockStates.getBlockState(blockPlaceContext.getLevel(), blockPlaceContext.getClickedPos());
+                }
+                final org.bukkit.block.BlockState oldBukkitState = bukkitState != null ? bukkitState : org.bukkit.craftbukkit.block.CraftBlockStates.getBlockState(blockPlaceContext.getLevel(), blockPlaceContext.getClickedPos()); // Paper - Reset placed block on exception
+                // CraftBukkit end
+
                 if (placementState == null) {
                     return InteractionResult.FAIL;
                 } else if (!this.placeBlock(blockPlaceContext, placementState)) {
@@ -69,15 +_,40 @@
                     BlockState blockState = level.getBlockState(clickedPos);
                     if (blockState.is(placementState.getBlock())) {
                         blockState = this.updateBlockStateFromTag(clickedPos, level, itemInHand, blockState);
+                        // Paper start - Reset placed block on exception
+                        try {
                         this.updateCustomBlockEntityTag(clickedPos, level, player, itemInHand, blockState);
                         updateBlockEntityComponents(level, clickedPos, itemInHand);
+                        } catch (Exception ex) {
+                            ((org.bukkit.craftbukkit.block.CraftBlockState) oldBukkitState).revertPlace();
+                            if (player instanceof ServerPlayer serverPlayer) {
+                                org.apache.logging.log4j.LogManager.getLogger().error("Player {} tried placing invalid block", player.getScoreboardName(), ex);
+                                serverPlayer.getBukkitEntity().kickPlayer("Packet processing error");
+                                return InteractionResult.FAIL;
+                            }
+                            throw ex; // Rethrow exception if not placed by a player
+                        }
+                        // Paper end - Reset placed block on exception
                         blockState.getBlock().setPlacedBy(level, clickedPos, blockState, player, itemInHand);
+                        // CraftBukkit start
+                        if (bukkitState != null) {
+                            org.bukkit.event.block.BlockPlaceEvent placeEvent = org.bukkit.craftbukkit.event.CraftEventFactory.callBlockPlaceEvent((net.minecraft.server.level.ServerLevel) level, player, blockPlaceContext.getHand(), bukkitState, clickedPos);
+                            if (placeEvent != null && (placeEvent.isCancelled() || !placeEvent.canBuild())) {
+                                ((org.bukkit.craftbukkit.block.CraftBlockState) bukkitState).revertPlace();
+
+                                // Paper - if the event is called here, the inventory should be updated
+                                player.containerMenu.sendAllDataToRemote(); // SPIGOT-4541
+                                return InteractionResult.FAIL;
+                            }
+                        }
+                        // CraftBukkit end
                         if (player instanceof ServerPlayer) {
                             CriteriaTriggers.PLACED_BLOCK.trigger((ServerPlayer)player, clickedPos, itemInHand);
                         }
                     }
 
                     SoundType soundType = blockState.getSoundType();
+                    if (player == null) // Paper - Fix block place logic; reintroduce this for the dispenser (i.e the shulker)
                     level.playSound(
                         player,
                         clickedPos,
@@ -137,8 +_,19 @@
 
     protected boolean canPlace(BlockPlaceContext context, BlockState state) {
         Player player = context.getPlayer();
-        return (!this.mustSurvive() || state.canSurvive(context.getLevel(), context.getClickedPos()))
-            && context.getLevel().isUnobstructed(state, context.getClickedPos(), CollisionContext.placementContext(player));
+        // CraftBukkit start
+        Level world = context.getLevel(); // Paper - Cancel hit for vanished players
+        boolean canBuild = (!this.mustSurvive() || state.canSurvive(world, context.getClickedPos())) && world.checkEntityCollision(state, player, CollisionContext.placementContext(player), context.getClickedPos(), true); // Paper - Cancel hit for vanished players
+        org.bukkit.entity.Player bukkitPlayer = (context.getPlayer() instanceof ServerPlayer) ? (org.bukkit.entity.Player) context.getPlayer().getBukkitEntity() : null;
+
+        org.bukkit.event.block.BlockCanBuildEvent event = new org.bukkit.event.block.BlockCanBuildEvent(
+            org.bukkit.craftbukkit.block.CraftBlock.at(world, context.getClickedPos()), bukkitPlayer,
+            org.bukkit.craftbukkit.block.data.CraftBlockData.fromData(state), canBuild, org.bukkit.craftbukkit.CraftEquipmentSlot.getHand(context.getHand())
+        );
+        world.getCraftServer().getPluginManager().callEvent(event);
+
+        return event.isBuildable();
+        // CraftBukkit end
     }
 
     protected boolean mustSurvive() {
@@ -167,7 +_,7 @@
                         return false;
                     }
 
-                    if (!type.onlyOpCanSetNbt() || player != null && player.canUseGameMasterBlocks()) {
+                    if (!type.onlyOpCanSetNbt() || player != null && (player.canUseGameMasterBlocks() || (player.getAbilities().instabuild && player.getBukkitEntity().hasPermission("minecraft.nbt.place")))) { // Spigot - add permission
                         return customData.loadInto(blockEntity, level.registryAccess());
                     }