Lazily track plugin scoreboards by default

On servers with plugins that constantly churn through scoreboards, there is a risk of
degraded GC performance due to the number of scoreboards held on by weak references.
Most plugins don't even need the (vanilla) functionality that requires all plugin
scoreboards to be tracked by the server. Instead, only track scoreboards when an
objective is added with a non-dummy criteria.

This is a breaking change, however the change is a much more sensible default. In case
this breaks your workflow you can always force all scoreboards to be tracked with
settings.track-plugin-scoreboards in paper.yml.

paper-server/src/main/java/org/bukkit/craftbukkit/scoreboard/CraftScoreboard.java

@@ -20,6 +20,7 @@ import org.bukkit.scoreboard.Team;
 
 public final class CraftScoreboard implements org.bukkit.scoreboard.Scoreboard {
     final Scoreboard board;
+    boolean registeredGlobally = false; // Paper - Lazily track plugin scoreboards by default
 
     CraftScoreboard(Scoreboard board) {
         this.board = board;
@@ -52,6 +53,12 @@ public final class CraftScoreboard implements org.bukkit.scoreboard.Scoreboard {
         Preconditions.checkArgument(renderType != null, "RenderType cannot be null");
         Preconditions.checkArgument(name.length() <= Short.MAX_VALUE, "The name '%s' is longer than the limit of 32767 characters (%s)", name, name.length());
         Preconditions.checkArgument(this.board.getObjective(name) == null, "An objective of name '%s' already exists", name);
+        // Paper start - lazily track plugin scoreboards
+        if (((CraftCriteria) criteria).criteria != net.minecraft.world.scores.criteria.ObjectiveCriteria.DUMMY && !this.registeredGlobally) {
+            net.minecraft.server.MinecraftServer.getServer().server.getScoreboardManager().registerScoreboardForVanilla(this);
+            this.registeredGlobally = true;
+        }
+        // Paper end - lazily track plugin scoreboards
         net.minecraft.world.scores.Objective objective = this.board.addObjective(name, ((CraftCriteria) criteria).criteria, io.papermc.paper.adventure.PaperAdventure.asVanilla(displayName), CraftScoreboardTranslations.fromBukkitRender(renderType), true, null);
         return new CraftObjective(this, objective);
     }

paper-server/src/main/java/org/bukkit/craftbukkit/scoreboard/CraftScoreboardManager.java

@@ -30,6 +30,7 @@ public final class CraftScoreboardManager implements ScoreboardManager {
 
     public CraftScoreboardManager(MinecraftServer minecraftserver, net.minecraft.world.scores.Scoreboard scoreboardServer) {
         this.mainScoreboard = new CraftScoreboard(scoreboardServer);
+        mainScoreboard.registeredGlobally = true; // Paper
         this.server = minecraftserver;
         this.scoreboards.add(this.mainScoreboard);
     }
@@ -43,10 +44,22 @@ public final class CraftScoreboardManager implements ScoreboardManager {
     public CraftScoreboard getNewScoreboard() {
         org.spigotmc.AsyncCatcher.catchOp("scoreboard creation"); // Spigot
         CraftScoreboard scoreboard = new CraftScoreboard(new ServerScoreboard(this.server));
-        this.scoreboards.add(scoreboard);
+        // Paper start
+        if (io.papermc.paper.configuration.GlobalConfiguration.get().scoreboards.trackPluginScoreboards) {
+            scoreboard.registeredGlobally = true;
+            scoreboards.add(scoreboard);
+        }
+        // Paper end
         return scoreboard;
     }
 
+    // Paper start
+    public void registerScoreboardForVanilla(CraftScoreboard scoreboard) {
+        org.spigotmc.AsyncCatcher.catchOp("scoreboard registration");
+        scoreboards.add(scoreboard);
+    }
+    // Paper end
+
     // CraftBukkit method
     public CraftScoreboard getPlayerBoard(CraftPlayer player) {
         CraftScoreboard board = this.playerBoards.get(player);