Restore World.loadChunkAsync API - but load chunks sync

We are still missing Async Chunk Loading, but plugins may be
depending on this API, so it missing blocks upgrading.

Spigot-API-Patches/0125-Add-async-chunk-load-API.patch

@@ -0,0 +1,92 @@
+From 50fe6b99320148740160eec04f499d03b57987dc Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Mon, 29 Feb 2016 17:43:33 -0600
+Subject: [PATCH] Add async chunk load API
+
+
+diff --git a/src/main/java/org/bukkit/World.java b/src/main/java/org/bukkit/World.java
+index 550c26be..121033e9 100644
+--- a/src/main/java/org/bukkit/World.java
++++ b/src/main/java/org/bukkit/World.java
+@@ -137,6 +137,78 @@ public interface World extends PluginMessageRecipient, Metadatable {
+      */
+     public Chunk getChunkAt(Block block);
+ 
++    /**
++     * Used by {@link World#getChunkAtAsync(Location,ChunkLoadCallback)} methods
++     * to request a {@link Chunk} to be loaded, with this callback receiving
++     * the chunk when it is finished.
++     *
++     * This callback will be executed on synchronously on the main thread.
++     *
++     * Timing and order this callback is fired is intentionally not defined and
++     * and subject to change.
++     */
++    public static interface ChunkLoadCallback {
++        public void onLoad(Chunk chunk);
++    }
++
++    /**
++     * Requests a {@link Chunk} to be loaded at the given coordinates
++     *
++     * This method makes no guarantee on how fast the chunk will load,
++     * and will return the chunk to the callback at a later time.
++     *
++     * You should use this method if you need a chunk but do not need it
++     * immediately, and you wish to let the server control the speed
++     * of chunk loads, keeping performance in mind.
++     *
++     * The {@link ChunkLoadCallback} will always be executed synchronously
++     * on the main Server Thread.
++     *
++     * @param x Chunk X-coordinate of the chunk - (world coordinate / 16)
++     * @param z Chunk Z-coordinate of the chunk - (world coordinate / 16)
++     * @param cb Callback to receive the chunk when it is loaded.
++     *           will be executed synchronously
++     */
++    public void getChunkAtAsync(int x, int z, ChunkLoadCallback cb);
++
++    /**
++     * Requests a {@link Chunk} to be loaded at the given {@link Location}
++     *
++     * This method makes no guarantee on how fast the chunk will load,
++     * and will return the chunk to the callback at a later time.
++     *
++     * You should use this method if you need a chunk but do not need it
++     * immediately, and you wish to let the server control the speed
++     * of chunk loads, keeping performance in mind.
++     *
++     * The {@link ChunkLoadCallback} will always be executed synchronously
++     * on the main Server Thread.
++     *
++     * @param location Location of the chunk
++     * @param cb Callback to receive the chunk when it is loaded.
++     *           will be executed synchronously
++     */
++    public void getChunkAtAsync(Location location, ChunkLoadCallback cb);
++
++    /**
++     * Requests {@link Chunk} to be loaded that contains the given {@link Block}
++     *
++     * This method makes no guarantee on how fast the chunk will load,
++     * and will return the chunk to the callback at a later time.
++     *
++     * You should use this method if you need a chunk but do not need it
++     * immediately, and you wish to let the server control the speed
++     * of chunk loads, keeping performance in mind.
++     *
++     * The {@link ChunkLoadCallback} will always be executed synchronously
++     * on the main Server Thread.
++     *
++     * @param block Block to get the containing chunk from
++     * @param cb Callback to receive the chunk when it is loaded.
++     *           will be executed synchronously
++     */
++    public void getChunkAtAsync(Block block, ChunkLoadCallback cb);
++
+     /**
+      * Checks if the specified {@link Chunk} is loaded
+      *
+-- 
+2.18.0
+

Spigot-Server-Patches/0302-Add-async-chunk-load-API.patch

@@ -0,0 +1,41 @@
+From 589d50e9902c7adfcd9837768bbcddbfdd809ebd Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Sat, 21 Jul 2018 16:55:04 -0400
+Subject: [PATCH] Add async chunk load API
+
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+index 0f4a894eb..995e02f1d 100644
+--- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
++++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+@@ -156,6 +156,27 @@ public class CraftWorld implements World {
+         }
+     }
+ 
++    // Paper start - Async chunk load API
++    public void getChunkAtAsync(final int x, final int z, final ChunkLoadCallback callback) {
++        final ChunkProviderServer cps = this.world.getChunkProviderServer();
++        callback.onLoad(cps.getChunkAt(x, z).bukkitChunk); // TODO: Add back async variant
++        /*cps.getChunkAt(x, z, new Runnable() {
++            @Override
++            public void run() {
++                callback.onLoad(cps.getChunkAt(x, z).bukkitChunk);
++            }
++        });*/
++    }
++
++    public void getChunkAtAsync(Block block, ChunkLoadCallback callback) {
++        getChunkAtAsync(block.getX() >> 4, block.getZ() >> 4, callback);
++    }
++
++    public void getChunkAtAsync(Location location, ChunkLoadCallback callback) {
++        getChunkAtAsync(location.getBlockX() >> 4, location.getBlockZ() >> 4, callback);
++    }
++    // Paper end
++
+     public Chunk getChunkAt(int x, int z) {
+         return this.world.getChunkProviderServer().getChunkAt(x, z).bukkitChunk;
+     }
+-- 
+2.18.0
+