Fix backpack IDs not incrementing (#4081)

src/main/java/io/github/thebusybiscuit/slimefun4/api/player/PlayerProfile.java

@@ -91,7 +91,10 @@ public class PlayerProfile {
      * Only intended for internal usage.
      * 
      * @return The {@link Config} associated with this {@link PlayerProfile}
+     *
+     * @deprecated Look at {@link PlayerProfile#getPlayerData()} instead for reading data.
      */
+    @Deprecated
     public @Nonnull Config getConfig() {
         return configFile;
     }
@@ -245,10 +248,9 @@ public class PlayerProfile {
     }
 
     public @Nonnull PlayerBackpack createBackpack(int size) {
-        IntStream stream = IntStream.iterate(0, i -> i + 1).filter(i -> !configFile.contains("backpacks." + i + ".size"));
+        int nextId = this.data.getBackpacks().size(); // Size is not 0 indexed so next ID can just be the current size
-        int id = stream.findFirst().getAsInt();
 
-        PlayerBackpack backpack = PlayerBackpack.newBackpack(this.ownerId, id, size);
+        PlayerBackpack backpack = PlayerBackpack.newBackpack(this.ownerId, nextId, size);
         this.data.addBackpack(backpack);
 
         markDirty();

src/test/java/io/github/thebusybiscuit/slimefun4/api/profiles/TestPlayerBackpacks.java

@@ -47,6 +47,21 @@ class TestPlayerBackpacks {
         Assertions.assertEquals(18, backpack.getInventory().getSize());
     }
 
+    @Test
+    @DisplayName("Test creating a new backpack will increment the id")
+    void testCreateBackpackIncrementsId() throws InterruptedException {
+        Player player = server.addPlayer();
+        PlayerProfile profile = TestUtilities.awaitProfile(player);
+
+        PlayerBackpack backpackOne = profile.createBackpack(18);
+        PlayerBackpack backpackTwo = profile.createBackpack(18);
+        PlayerBackpack backpackThree = profile.createBackpack(18);
+
+        Assertions.assertEquals(0, backpackOne.getId());
+        Assertions.assertEquals(1, backpackTwo.getId());
+        Assertions.assertEquals(2, backpackThree.getId());
+    }
+
     @Test
     @DisplayName("Test upgrading the backpack size")
     void testChangeSize() throws InterruptedException {