After clicking "Delete World", hardcore world still runs in background

Can confirm.

EDIT: Apparently, after the world is "Deleted", the area that you died in said world shows up in various menus.

Confirmed for 16w05b.

Confirmed 16w07a.

@unknown, since you're the reporter of this ticket, you can update the affected versions list by yourself (and you don't need to leave a comment "Confirmed XXYY")

Thanks for pointing that out, Kumasasa. I'm kinda slow. But I've updated it to show 1.9-pre1 now.

I accidentally made a dupe of this in MC-98939. It appears that the world is still loaded in memory and running and so you can't completely delete it until you exit out of minecraft.

Confirmed for 1.13.1.

I seem to have found the source of the issue.

To sum it up, inside of GuiGameOver.java when the game checks if the world was in hardcore, it only changes the GuiScreen to the Main Menu without sending the normal disconnect packet.

Specifically in the actionPreformed function of GuiGameOver.java the if statement

if (this.mc.world.getWorldInfo().isHardcoreModeEnabled()) {
    this.mc.displayGuiScreen(new GuiMainMenu());
}

should more closely mirror the functionality of the confirmClicked function (where result is a boolean that is true if the player clicked "Title Screen" after dying).

if (result) {
    if (this.mc.world != null) {
        this.mc.world.sendQuittingDisconnectingPacket();
    }

    this.mc.loadWorld((WorldClient)null);
    this.mc.displayGuiScreen(new GuiMainMenu());
}

The fixed code is the following (for actionPerformed in GuiGameOver.java ~line 75)

if (this.mc.world.getWorldInfo().isHardcoreModeEnabled()) {
    //Changed
    if (this.mc.world != null) {
        this.mc.world.sendQuittingDisconnectingPacket();
    }

    this.mc.loadWorld((WorldClient)null);
    //
    this.mc.displayGuiScreen(new GuiMainMenu());
}

This issue can have severe consequence when trying to rejoin the world in the background after hitting "delete world", it will freeze the game.

When "Delete World" is pressed, you are sent to the menu which has a white screen (white-menu-background.png) [MC-148865]. If you try and Edit the world's options, it will overlay the in-game events (edit-world-options.png). If you try to join the Hardcore world you just left the screen will go black and the game will be completely unresponsive (rejoin-hardcore-world.png).

Being unable to delete world 1.14.3 pre 4 confirmed. Can't delete it from the saves menu or windows explorer either. And you don't have to die to be unable to delete hardcore worlds.

Still confirmed for 1.14.4 release

Issue is still existing in 1.14.4

Screen is from me trying enter that type of world 😛
Game is still running 

Fix to this issue in 1.14.4 is simple:

Tested on custom MCP 1.14.4

In `confirmCallback` after sending packet of disconnecting

SaveFormat saveformat = this.minecraft.getSaveLoader();
for (WorldSummary worldSummary : WorldSelectionList.field_212331_y) {
    if (this.minecraft.player.world.getWorldInfo().getWorldName() == worldSummary.getDisplayName()) {
        saveformat.deleteWorldDirectory(worldSummary.getFileName());
    }
}

and in button action add code below before function displaying main menu

this.confirmCallback(true);

@edit
forgot to mention about changeing access for

private List<WorldSummary> field_212331_y;

from `private` to `public static`

Yeah that happened to me once too. Also, did anyone else who got this bug have a tough time ending the Minecraft Java Program? I had a tough time stopping the game.

Was fixed in 19w35a, see MC-30646 for details.