refactor: remove fallback server names, require explicit queue group servers

Replace silent fallbacks with validation errors when queue groups have
empty server lists. Add missing @comment on forceTargetServer. Remove
redundant forced target-server inclusion in kickWhenDownServers.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: AlexProgrammerDE

shared/src/main/java/net/pistonmaster/pistonqueue/shared/config/Config.java

@@ -119,6 +119,7 @@ public final class Config {
   @Comment("Load balancing strategy for multiple queue servers: ROUND_ROBIN, LEAST_PLAYERS, RANDOM")
   private LoadBalancingStrategy queueLoadBalancing = LoadBalancingStrategy.LEAST_PLAYERS;
 
+  @Comment("Ignore the player's intended target server and always use the queue group's default target.")
   private boolean forceTargetServer = false;
 
   @Comment({
@@ -127,13 +128,6 @@ public final class Config {
   })
   private boolean enableSourceServer = false;
 
-  @Ignore
-  private String queueServer = "queue";
-  @Ignore
-  private String targetServer = "main";
-  @Ignore
-  private String sourceServer = "lobby";
-
   @Comment("Connecting to server message")
   private String joiningTargetServer = "&6Connecting to the server...";
 
@@ -621,12 +615,6 @@ private void rebuildKickWhenDownServers() {
         }
       }
     }
-    // Always include all target servers
-    for (String target : allTargetServers) {
-      if (!resolved.contains(target)) {
-        resolved.add(target);
-      }
-    }
     kickWhenDownServers = resolved;
   }
 
@@ -688,17 +676,17 @@ private void rebuildQueueGroups() {
 
       List<String> resolvedQueueServers = configuration.getQueueServers();
       if (resolvedQueueServers.isEmpty()) {
-        resolvedQueueServers = List.of(queueServer);
+        throw new IllegalStateException("Queue group \"" + name + "\" must specify at least one queue server");
       }
 
       List<String> targetServers = configuration.getTargetServers();
       if (targetServers.isEmpty()) {
-        targetServers = List.of(targetServer);
+        throw new IllegalStateException("Queue group \"" + name + "\" must specify at least one target server");
       }
 
       List<String> sourceServers = enableSourceServer ? configuration.getSourceServers() : List.of();
-      if (enableSourceServer && sourceServers.isEmpty() && sourceServer != null && !sourceServer.isBlank()) {
-        sourceServers = List.of(sourceServer);
+      if (enableSourceServer && sourceServers.isEmpty()) {
+        throw new IllegalStateException("Queue group \"" + name + "\" must specify at least one source server when enableSourceServer is true");
       }
 
       List<String> typeNames = configuration.getQueueTypes();
@@ -833,9 +821,9 @@ private Map<String, QueueTypeConfiguration> defaultQueueTypes() {
   private Map<String, QueueGroupConfiguration> defaultQueueGroups() {
     Map<String, QueueGroupConfiguration> defaults = new LinkedHashMap<>();
     QueueGroupConfiguration configuration = new QueueGroupConfiguration();
-    configuration.queueServers = new ArrayList<>(List.of(queueServer));
-    configuration.targetServers = new ArrayList<>(List.of(targetServer));
-    configuration.sourceServers = new ArrayList<>(List.of(sourceServer));
+    configuration.queueServers = new ArrayList<>(List.of("queue"));
+    configuration.targetServers = new ArrayList<>(List.of("main"));
+    configuration.sourceServers = new ArrayList<>(List.of("lobby"));
     configuration.queueTypes = new ArrayList<>(queueTypes.keySet());
     configuration.defaultGroup = true;
     defaults.put("default", configuration);

shared/src/test/java/net/pistonmaster/pistonqueue/shared/config/ConfigTest.java

@@ -235,7 +235,7 @@ void queueGroupReferencingUnknownTypeThrows() {
 
     Config.QueueGroupConfiguration groupConfig = new Config.QueueGroupConfiguration();
     groupConfig.setDefaultGroup(true);
-    groupConfig.setQueueServers(List.of());
+    groupConfig.setQueueServers(List.of("queue"));
     groupConfig.setTargetServers(List.of("main"));
     groupConfig.setSourceServers(List.of());
     groupConfig.setQueueTypes(List.of("NONEXISTENT_TYPE"));
@@ -290,7 +290,7 @@ private Config createConfigWithMultipleQueueTypes() {
 
     Config.QueueGroupConfiguration groupConfig = new Config.QueueGroupConfiguration();
     groupConfig.setDefaultGroup(true);
-    groupConfig.setQueueServers(List.of());
+    groupConfig.setQueueServers(List.of("queue"));
     groupConfig.setTargetServers(List.of("main"));
     groupConfig.setSourceServers(List.of());
     groupConfig.setQueueTypes(List.of("VETERAN", "PRIORITY", "REGULAR"));
@@ -313,7 +313,7 @@ private Config createConfigWithNoDefaultType() {
 
     Config.QueueGroupConfiguration groupConfig = new Config.QueueGroupConfiguration();
     groupConfig.setDefaultGroup(true);
-    groupConfig.setQueueServers(List.of());
+    groupConfig.setQueueServers(List.of("queue"));
     groupConfig.setTargetServers(List.of("main"));
     groupConfig.setSourceServers(List.of());
     groupConfig.setQueueTypes(List.of("VIP", "PREMIUM"));

shared/src/test/java/net/pistonmaster/pistonqueue/shared/queue/logic/QueuePlacementCoordinatorTest.java

@@ -164,8 +164,6 @@ void disconnectsWhenRequiredServerDown() {
   @Test
   void skipsQueueWhenSourceServerUnsupported() {
     Config config = QueueTestUtils.createConfigWithSingleQueueType(1);
-    String targetServer = QueueTestUtils.defaultTargetServer(config);
-    config.setEnableSourceServer(true);
 
     // Rebuild groups with source server
     Config.QueueGroupConfiguration groupConfig = new Config.QueueGroupConfiguration();
@@ -175,6 +173,8 @@ void skipsQueueWhenSourceServerUnsupported() {
     groupConfig.setSourceServers(List.of("lobby"));
     groupConfig.setQueueTypes(List.of("DEFAULT"));
     config.setQueueGroupDefinitions(java.util.Map.of("default", groupConfig));
+    config.setEnableSourceServer(true);
+    String targetServer = QueueTestUtils.defaultTargetServer(config);
 
     QueueType type = config.getAllQueueTypes().getFirst();
     type.getPlayersWithTypeInTarget().set(1);
@@ -191,8 +191,6 @@ void skipsQueueWhenSourceServerUnsupported() {
   @Test
   void queuesWhenSourceMatchesRequirement() {
     Config config = QueueTestUtils.createConfigWithSingleQueueType(1);
-    String targetServer = QueueTestUtils.defaultTargetServer(config);
-    config.setEnableSourceServer(true);
 
     // Rebuild groups with source server
     Config.QueueGroupConfiguration groupConfig = new Config.QueueGroupConfiguration();
@@ -202,6 +200,8 @@ void queuesWhenSourceMatchesRequirement() {
     groupConfig.setSourceServers(List.of("lobby"));
     groupConfig.setQueueTypes(List.of("DEFAULT"));
     config.setQueueGroupDefinitions(java.util.Map.of("default", groupConfig));
+    config.setEnableSourceServer(true);
+    String targetServer = QueueTestUtils.defaultTargetServer(config);
 
     QueueType type = config.getAllQueueTypes().getFirst();
     type.getPlayersWithTypeInTarget().set(1);

shared/src/test/java/net/pistonmaster/pistonqueue/shared/queue/logic/QueueTestUtils.java

@@ -94,8 +94,8 @@ static Config createConfigWithSingleQueueType(int slots) {
 
     Config.QueueGroupConfiguration groupConfiguration = new Config.QueueGroupConfiguration();
     groupConfiguration.setDefaultGroup(true);
-    groupConfiguration.setQueueServers(List.of());
-    groupConfiguration.setTargetServers(List.of());
+    groupConfiguration.setQueueServers(List.of("queue"));
+    groupConfiguration.setTargetServers(List.of("target"));
     groupConfiguration.setSourceServers(List.of());
     groupConfiguration.setQueueTypes(List.of("DEFAULT"));