WorldArgument fails java.lang.NoClassDefFoundError: org/bukkit/generator/WorldInfo in Minecraft 1.16.5

[JorelAli]

CommandAPI version

8.7.2

Minecraft version

1.16.5

Are you shading the CommandAPI?

Yes

What I did

Instantiate a WorldArgument in your onEnable() method and run this on a 1.16.5 server:

new WorldArgument();

What actually happened

Fails due to WorldInfo class not existing

[13:34:14 ERROR]: Error occurred while enabling CommandAPI v9.0.0-SNAPSHOT (Is it up to date?)
java.lang.NoClassDefFoundError: org/bukkit/generator/WorldInfo
        at dev.jorel.commandapi.CommandAPIMain.onEnable(CommandAPIMain.java:136) ~[?:?]
        at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:263) ~[patched_1.16.5.jar:git-Paper-794]
        at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:370) ~[patched_1.16.5.jar:git-Paper-794]
        at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:500) ~[patched_1.16.5.jar:git-Paper-794]
        at org.bukkit.craftbukkit.v1_16_R3.CraftServer.enablePlugin(CraftServer.java:518) ~[patched_1.16.5.jar:git-Paper-794]
        at org.bukkit.craftbukkit.v1_16_R3.CraftServer.enablePlugins(CraftServer.java:432) ~[patched_1.16.5.jar:git-Paper-794]
        at net.minecraft.server.v1_16_R3.MinecraftServer.loadWorld(MinecraftServer.java:599) ~[patched_1.16.5.jar:git-Paper-794]
        at net.minecraft.server.v1_16_R3.DedicatedServer.init(DedicatedServer.java:298) ~[patched_1.16.5.jar:git-Paper-794]
        at net.minecraft.server.v1_16_R3.MinecraftServer.w(MinecraftServer.java:1074) ~[patched_1.16.5.jar:git-Paper-794]
        at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$a$0(MinecraftServer.java:291) ~[patched_1.16.5.jar:git-Paper-794]
        at java.lang.Thread.run(Thread.java:833) [?:?]
Caused by: java.lang.ClassNotFoundException: org.bukkit.generator.WorldInfo
        at org.bukkit.plugin.java.PluginClassLoader.loadClass0(PluginClassLoader.java:155) ~[patched_1.16.5.jar:git-Paper-794]
        at org.bukkit.plugin.java.PluginClassLoader.loadClass(PluginClassLoader.java:114) ~[patched_1.16.5.jar:git-Paper-794]
        at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?]
        ... 11 more

What should have happened

Loads normally

Server logs and CommandAPI config

No response

Other

This issue is caused by the method reference lambda in the WorldArgument constructor to convert a World to a String:

((Function<World, String>) World::getName).andThen(String::toLowerCase)

The generated source code:

SourceFile: "WorldArgument.java"
Signature: #88                          // Ldev/jorel/commandapi/arguments/SafeOverrideableArgument<Lorg/bukkit/World;Lorg/bukkit/World;>;
BootstrapMethods:
  0: #96 REF_invokeStatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
    Method arguments:
      #98 (Ljava/lang/Object;)Ljava/lang/Object;
      #105 REF_invokeInterface org/bukkit/generator/WorldInfo.getName:()Ljava/lang/String;
      #107 (Lorg/bukkit/World;)Ljava/lang/String;
  1: #96 REF_invokeStatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
    Method arguments:
      #108 (Ljava/lang/Object;)Ljava/lang/Object;
      #114 REF_invokeVirtual java/lang/String.toLowerCase:()Ljava/lang/String;
      #116 (Ljava/lang/String;)Ljava/lang/String;
InnerClasses:
  public static final #122= #118 of #120; // Lookup=class java/lang/invoke/MethodHandles$Lookup of class java/lang/invoke/MethodHandles

The generated source code of just using a lambda directly:

world -> world.getName().toLowerCase()

  private static java.lang.String lambda$0(org.bukkit.World);
    descriptor: (Lorg/bukkit/World;)Ljava/lang/String;
    flags: (0x100a) ACC_PRIVATE, ACC_STATIC, ACC_SYNTHETIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokeinterface #81,  1           // InterfaceMethod org/bukkit/World.getName:()Ljava/lang/String;
         6: invokevirtual #85                 // Method java/lang/String.toLowerCase:()Ljava/lang/String;
         9: areturn
      LineNumberTable:
        line 42: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0      10     0 world   Lorg/bukkit/World;
}
SourceFile: "WorldArgument.java"
Signature: #94                          // Ldev/jorel/commandapi/arguments/SafeOverrideableArgument<Lorg/bukkit/World;Lorg/bukkit/World;>;
BootstrapMethods:
  0: #102 REF_invokeStatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
    Method arguments:
      #104 (Ljava/lang/Object;)Ljava/lang/Object;
      #107 REF_invokeStatic dev/jorel/commandapi/arguments/WorldArgument.lambda$0:(Lorg/bukkit/World;)Ljava/lang/String;
      #108 (Lorg/bukkit/World;)Ljava/lang/String;
InnerClasses:
  public static final #114= #110 of #112; // Lookup=class java/lang/invoke/MethodHandles$Lookup of class java/lang/invoke/MethodHandles

As you can see, with the method reference it references the WorldInfo class which the World class extends in 1.19.2, but does not extend (or exist) in 1.16.5.