Update legacy world name on world load

src/main/java/org/mvplugins/multiverse/core/world/LoadedMultiverseWorld.java

@@ -55,6 +55,7 @@ private void setupWorldConfig(World world) {
         worldConfig.load();
         worldConfig.setEnvironment(world.getEnvironment());
         worldConfig.setSeed(world.getSeed());
+        worldConfig.setLegacyWorldName(world.getName());
     }
 
     private void setupSpawnLocation(World world) {

src/main/java/org/mvplugins/multiverse/core/world/WorldConfigNodes.java

@@ -306,6 +306,8 @@ public Object serialize(EntitySpawnConfig object, Class<EntitySpawnConfig> type)
             .hidden());
 
     final ConfigNode<String> legacyWorldName = node(ConfigNode.builder("read-only.legacy-world-name", String.class)
+            .onLoadAndChange((oldValue, newValue) -> worldManager.getWorldStore().changeLegacyWorldName(
+                    oldValue, newValue, keyOrName.usableKey()))
             .hidden());
 
     final ConfigNode<Long> seed = node(ConfigNode.builder("read-only.seed", Long.class)

src/main/java/org/mvplugins/multiverse/core/world/WorldStore.java

@@ -120,6 +120,29 @@ void removeLoadedWorld(LoadedMultiverseWorld world) {
         unloadedList.add(unloadedMap.get(world.getKey().toString()));
     }
 
+    void changeLegacyWorldName(@Nullable String oldName, @Nullable String newName, @NotNull NamespacedKey worldKey) {
+        if (Objects.equals(oldName, newName)) {
+            return;
+        }
+        String key = worldKey.toString();
+        updateLegacyWorldName(loadedMap, oldName, newName, key);
+        updateLegacyWorldName(unloadedMap, oldName, newName, key);
+    }
+
+    private <T extends MultiverseWorld> void updateLegacyWorldName(
+            Map<String, T> map, @Nullable String oldName, @Nullable String newName, String key) {
+        T world = map.get(key);
+        if (world == null) {
+            return;
+        }
+        if (oldName != null && !key.equalsIgnoreCase(oldName)) {
+            map.remove(oldName, world);
+        }
+        if (newName != null) {
+            map.put(newName, world);
+        }
+    }
+
     void changeAlias(@Nullable String oldAlias, @Nullable String newAlias, @NotNull NamespacedKey worldKey) {
         if (Objects.equals(oldAlias, newAlias)) {
             // nothing changed, ignore

src/test/java/org/mvplugins/multiverse/core/world/WorldManagerTest.kt

@@ -49,6 +49,38 @@ class WorldManagerTest : TestWithMockBukkit() {
         assertNotNull(world2)
     }
 
+    @Test
+    fun `Legacy world name changes update loaded and unloaded lookups`() {
+        val worldKey = world.key.toString()
+        assertTrue(world.worldConfig.setLegacyWorldName("renamed_world").isSuccess)
+
+        assertFalse(worldManager.getWorld("world").isDefined)
+        assertSame(world, worldManager.getLoadedWorld("RENAMED_WORLD").get())
+        assertSame(world, worldManager.getLoadedWorld(worldKey).get())
+
+        assertTrue(worldManager.unloadWorld(UnloadWorldOptions.world(world)).isSuccess)
+        assertFalse(worldManager.getWorld("world").isDefined)
+        assertFalse(worldManager.getLoadedWorld("renamed_world").isDefined)
+        assertEquals(world.key, worldManager.getUnloadedWorld("RENAMED_WORLD").get().key)
+        assertEquals(world.key, worldManager.getUnloadedWorld(worldKey).get().key)
+    }
+
+    @Test
+    fun `Setting up loaded world config refreshes legacy world name lookups`() {
+        assertTrue(world.worldConfig.setLegacyWorldName("stale_name").isSuccess)
+        assertTrue(world.worldConfig.save().isSuccess)
+
+        world.setWorldConfig(world.worldConfig)
+
+        assertEquals("world", world.name)
+        assertSame(world, worldManager.getLoadedWorld("world").get())
+        assertFalse(worldManager.getWorld("stale_name").isDefined)
+
+        assertTrue(worldManager.unloadWorld(UnloadWorldOptions.world(world)).isSuccess)
+        assertTrue(worldManager.getUnloadedWorld("world").isDefined)
+        assertFalse(worldManager.getWorld("stale_name").isDefined)
+    }
+
     @Test
     fun `Create world with custom options`() {
         assertTrue(worldManager.createWorld(