Added a hack to allow tiles to trigger client-side render updates on blocks without actually changing the block

Bedrock block entity updates don't directly trigger block rendering
updates. This is a problem when the block entity data affects the
block's appearance directly (e.g. cauldron water colour, flower pot
contents), because it means changing them won't directly result in a
client-side render update.

This hack allows tiles to spoof block updates without actually changing
the server-side block, keeping the internals and API clean of random
shitbox workarounds.

fixes #5174
fixes #4944

src/block/tile/Spawnable.php

@@ -23,7 +23,11 @@ declare(strict_types=1);
 
 namespace pocketmine\block\tile;
 
+use pocketmine\block\Block;
+use pocketmine\nbt\tag\ByteTag;
 use pocketmine\nbt\tag\CompoundTag;
+use pocketmine\nbt\tag\IntTag;
+use pocketmine\nbt\tag\StringTag;
 use pocketmine\network\mcpe\protocol\types\CacheableNbt;
 use function get_class;
 
@@ -49,6 +53,22 @@ abstract class Spawnable extends Tile{
 		$this->spawnCompoundCache = null;
 	}
 
+	/**
+	 * The Bedrock client won't re-render a block if the block's state properties didn't change. This is a problem when
+	 * the tile may affect the block's appearance. For example, a cauldron's liquid changes colour based on the dye
+	 * inside.
+	 *
+	 * This is worked around in vanilla by modifying one of the block's state properties to a different value, and then
+	 * changing it back again. Since we don't want to litter core implementation with hacks like this, we brush it under
+	 * the rug into Tile.
+	 *
+	 * @return ByteTag[]|IntTag[]|StringTag[]
+	 * @phpstan-return array<string, IntTag|StringTag|ByteTag>
+	 */
+	public function getRenderUpdateBugWorkaroundStateProperties(Block $block) : array{
+		return [];
+	}
+
 	/**
 	 * Returns encoded NBT (varint, little-endian) used to spawn this tile to clients. Uses cache where possible,
 	 * populates cache if it is null.