Add configuration option to prevent player names from being suggested

paper-api/src/main/java/org/bukkit/Bukkit.java

@@ -2412,6 +2412,16 @@ public final class Bukkit {
     public static boolean reloadCommandAliases() {
         return server.reloadCommandAliases();
     }
+
+    /**
+     * Checks if player names should be suggested when a command returns {@code null} as
+     * their tab completion result.
+     *
+     * @return true if player names should be suggested
+     */
+    public static boolean suggestPlayerNamesWhenNullTabCompletions() {
+        return server.suggestPlayerNamesWhenNullTabCompletions();
+    }
     // Paper end
 
     @NotNull

paper-api/src/main/java/org/bukkit/Server.java

@@ -2100,4 +2100,14 @@ public interface Server extends PluginMessageRecipient, net.kyori.adventure.audi
     void reloadPermissions(); // Paper
 
     boolean reloadCommandAliases(); // Paper
+
+    // Paper start - allow preventing player name suggestions by default
+    /**
+     * Checks if player names should be suggested when a command returns {@code null} as
+     * their tab completion result.
+     *
+     * @return true if player names should be suggested
+     */
+    boolean suggestPlayerNamesWhenNullTabCompletions();
+    // Paper end
 }

paper-api/src/main/java/org/bukkit/command/Command.java

@@ -107,7 +107,7 @@ public abstract class Command {
         Preconditions.checkArgument(args != null, "Arguments cannot be null");
         Preconditions.checkArgument(alias != null, "Alias cannot be null");
 
-        if (args.length == 0) {
+        if (args.length == 0 || !sender.getServer().suggestPlayerNamesWhenNullTabCompletions()) { // Paper - allow preventing player name suggestions by default) {
             return ImmutableList.of();
         }