[1.16.5] Backport OnDatapackSyncEvent from 1.17.1 (#7985)

patches/minecraft/net/minecraft/server/management/PlayerList.java.patch

@@ -16,8 +16,11 @@
        GameRules gamerules = serverworld1.func_82736_K();
        boolean flag = gamerules.func_223586_b(GameRules.field_226683_z_);
        boolean flag1 = gamerules.func_223586_b(GameRules.field_223612_o);
-@@ -156,6 +_,7 @@
+@@ -154,8 +_,10 @@
+       serverplaynethandler.func_147359_a(new SServerDifficultyPacket(iworldinfo.func_176130_y(), iworldinfo.func_176123_z()));
+       serverplaynethandler.func_147359_a(new SPlayerAbilitiesPacket(p_72355_2_.field_71075_bZ));
        serverplaynethandler.func_147359_a(new SHeldItemChangePacket(p_72355_2_.field_71071_by.field_70461_c));
++      net.minecraftforge.common.MinecraftForge.EVENT_BUS.post(new net.minecraftforge.event.OnDatapackSyncEvent(this, p_72355_2_));
        serverplaynethandler.func_147359_a(new SUpdateRecipesPacket(this.field_72400_f.func_199529_aN().func_199510_b()));
        serverplaynethandler.func_147359_a(new STagsListPacket(this.field_72400_f.func_244266_aF()));
 +      net.minecraftforge.fml.network.NetworkHooks.syncCustomTagTypes(p_72355_2_, this.field_72400_f.func_244266_aF());
@@ -137,9 +140,11 @@
     }
  
     @Nullable
-@@ -804,6 +_,7 @@
+@@ -803,7 +_,9 @@
+          playeradvancements.func_240918_a_(this.field_72400_f.func_191949_aK());
        }
  
++      net.minecraftforge.common.MinecraftForge.EVENT_BUS.post(new net.minecraftforge.event.OnDatapackSyncEvent(this, null));
        this.func_148540_a(new STagsListPacket(this.field_72400_f.func_244266_aF()));
 +      net.minecraftforge.fml.network.NetworkHooks.syncCustomTagTypes(this.field_72400_f.func_244266_aF());
        SUpdateRecipesPacket supdaterecipespacket = new SUpdateRecipesPacket(this.field_72400_f.func_199529_aN().func_199510_b());

src/main/java/net/minecraftforge/event/OnDatapackSyncEvent.java

@@ -0,0 +1,43 @@
+package net.minecraftforge.event;
+
+import javax.annotation.Nullable;
+
+import net.minecraft.entity.player.ServerPlayerEntity;
+import net.minecraft.server.management.PlayerList;
+import net.minecraftforge.eventbus.api.Event;
+
+/**
+ * Fires when a player joins the server or when the reload command is ran,
+ * before tags and crafting recipes are sent to the client. Send datapack data
+ * to clients when this event fires.
+ */
+public class OnDatapackSyncEvent extends Event
+{
+    private final PlayerList playerList;
+    @Nullable
+    private final ServerPlayerEntity player;
+
+    public OnDatapackSyncEvent(PlayerList playerList, @Nullable ServerPlayerEntity player)
+    {
+        this.playerList = playerList;
+        this.player = player;
+    }
+
+    /**
+     * @return The server's player list to get a view of all players.
+     */
+    public PlayerList getPlayerList()
+    {
+        return this.playerList;
+    }
+
+    /**
+     * @return The player to sync datapacks to. Null when syncing for all players,
+     *         such as when the reload command runs.
+     */
+    @Nullable
+    public ServerPlayerEntity getPlayer()
+    {
+        return this.player;
+    }
+}

src/test/java/net/minecraftforge/debug/misc/OnDatapackSynctEventTest.java

@@ -0,0 +1,32 @@
+package net.minecraftforge.debug.misc;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import net.minecraft.entity.player.ServerPlayerEntity;
+import net.minecraftforge.event.OnDatapackSyncEvent;
+import net.minecraftforge.eventbus.api.SubscribeEvent;
+import net.minecraftforge.fml.common.Mod;
+
+@Mod("send_datapacks_to_client")
+@Mod.EventBusSubscriber
+public class OnDatapackSynctEventTest
+{
+    private static final Logger LOGGER = LogManager.getLogger();
+
+    @SubscribeEvent
+    protected static void onSendDataToClient(final OnDatapackSyncEvent event)
+    {
+        // Fire for a specific player on login
+        if (event.getPlayer() != null)
+            syncData(event.getPlayer());
+        // Fire for all players on /reload
+        else
+            event.getPlayerList().getPlayers().forEach(OnDatapackSynctEventTest::syncData);
+    }
+
+    private static void syncData(ServerPlayerEntity player)
+    {
+        LOGGER.info("Sending modded datapack data to {}", player.getName().getString());
+    }
+}

src/test/resources/META-INF/mods.toml

@@ -138,3 +138,7 @@ license="LGPL v2.1"
     modId="dimension_settings_test"
 [[mods]]
     modId="player_attack_knockback_test"
+[[mods]]
+    modId="send_datapacks_to_client"
+
+# ADD ABOVE THIS LINE