MultiServer, customserver, CI, Test: Fix problems in room hosting and test/simulate it (#3464)

* Test: add hosting simulation test

* WebHost: add weak typing to get_app()

* MultiServer: add typing to auto_saver_thread

* MultiServer: don't cancel task, properly end it

* customserver: stop auto-save thread from saving after shutdown

and make sure it stops, another potential memory leak

* MultiServer, customserver: make datapackage small again

* customserver: collect/finish room tasks

Hopefully fixes the memory leak we are seeing

* CI: test hosting

* Test: hosting: verify autohoster saves on Ctrl+C

* customserver: save when stopping via Ctrl+C

test/hosting/__main__.py

@@ -0,0 +1,191 @@
+# A bunch of tests to verify MultiServer and custom webhost server work as expected.
+# This spawns processes and may modify your local AP, so this is not run as part of unit testing.
+# Run with `python test/hosting` instead,
+import logging
+import traceback
+from tempfile import TemporaryDirectory
+from time import sleep
+from typing import Any
+
+from test.hosting.client import Client
+from test.hosting.generate import generate_local
+from test.hosting.serve import ServeGame, LocalServeGame, WebHostServeGame
+from test.hosting.webhost import (create_room, get_app, get_multidata_for_room, set_multidata_for_room, start_room,
+                                  stop_autohost, upload_multidata)
+from test.hosting.world import copy as copy_world, delete as delete_world
+
+failure = False
+fail_fast = True
+
+
+def assert_true(condition: Any, msg: str = "") -> None:
+    global failure
+    if not condition:
+        failure = True
+        msg = f": {msg}" if msg else ""
+        raise AssertionError(f"Assertion failed{msg}")
+
+
+def assert_equal(first: Any, second: Any, msg: str = "") -> None:
+    global failure
+    if first != second:
+        failure = True
+        msg = f": {msg}" if msg else ""
+        raise AssertionError(f"Assertion failed: {first} == {second}{msg}")
+
+
+if fail_fast:
+    expect_true = assert_true
+    expect_equal = assert_equal
+else:
+    def expect_true(condition: Any, msg: str = "") -> None:
+        global failure
+        if not condition:
+            failure = True
+            tb = "".join(traceback.format_stack()[:-1])
+            msg = f": {msg}" if msg else ""
+            logging.error(f"Expectation failed{msg}\n{tb}")
+
+    def expect_equal(first: Any, second: Any, msg: str = "") -> None:
+        global failure
+        if first != second:
+            failure = True
+            tb = "".join(traceback.format_stack()[:-1])
+            msg = f": {msg}" if msg else ""
+            logging.error(f"Expectation failed {first} == {second}{msg}\n{tb}")
+
+
+if __name__ == "__main__":
+    import warnings
+    warnings.simplefilter("ignore", ResourceWarning)
+    warnings.simplefilter("ignore", UserWarning)
+
+    spacer = '=' * 80
+
+    with TemporaryDirectory() as tempdir:
+        multis = [["Clique"], ["Temp World"], ["Clique", "Temp World"]]
+        p1_games = []
+        data_paths = []
+        rooms = []
+
+        copy_world("Clique", "Temp World")
+        try:
+            for n, games in enumerate(multis, 1):
+                print(f"Generating [{n}] {', '.join(games)}")
+                multidata = generate_local(games, tempdir)
+                print(f"Generated [{n}] {', '.join(games)} as {multidata}\n")
+                p1_games.append(games[0])
+                data_paths.append(multidata)
+        finally:
+            delete_world("Temp World")
+
+        webapp = get_app(tempdir)
+        webhost_client = webapp.test_client()
+        for n, multidata in enumerate(data_paths, 1):
+            seed = upload_multidata(webhost_client, multidata)
+            room = create_room(webhost_client, seed)
+            print(f"Uploaded [{n}] {multidata} as {room}\n")
+            rooms.append(room)
+
+        print("Starting autohost")
+        from WebHostLib.autolauncher import autohost
+        try:
+            autohost(webapp.config)
+
+            host: ServeGame
+            for n, (multidata, room, game, multi_games) in enumerate(zip(data_paths, rooms, p1_games, multis), 1):
+                involved_games = {"Archipelago"} | set(multi_games)
+                for collected_items in range(3):
+                    print(f"\nTesting [{n}] {game} in {multidata} on MultiServer with {collected_items} items collected")
+                    with LocalServeGame(multidata) as host:
+                        with Client(host.address, game, "Player1") as client:
+                            local_data_packages = client.games_packages
+                            local_collected_items = len(client.checked_locations)
+                            if collected_items < 2:  # Clique only has 2 Locations
+                                client.collect_any()
+                            # TODO: Ctrl+C test here as well
+
+                    for game_name in sorted(involved_games):
+                        expect_true(game_name in local_data_packages,
+                                    f"{game_name} missing from MultiServer datap ackage")
+                        expect_true("item_name_groups" not in local_data_packages.get(game_name, {}),
+                                    f"item_name_groups are not supposed to be in MultiServer data for {game_name}")
+                        expect_true("location_name_groups" not in local_data_packages.get(game_name, {}),
+                                    f"location_name_groups are not supposed to be in MultiServer data for {game_name}")
+                    for game_name in local_data_packages:
+                        expect_true(game_name in involved_games,
+                                    f"Received unexpected extra data package for {game_name} from MultiServer")
+                    assert_equal(local_collected_items, collected_items,
+                                 "MultiServer did not load or save correctly")
+
+                    print(f"\nTesting [{n}] {game} in {multidata} on customserver with {collected_items} items collected")
+                    prev_host_adr: str
+                    with WebHostServeGame(webhost_client, room) as host:
+                        prev_host_adr = host.address
+                        with Client(host.address, game, "Player1") as client:
+                            web_data_packages = client.games_packages
+                            web_collected_items = len(client.checked_locations)
+                            if collected_items < 2:  # Clique only has 2 Locations
+                                client.collect_any()
+                            if collected_items == 1:
+                                sleep(1)  # wait for the server to collect the item
+                                stop_autohost(True)  # simulate Ctrl+C
+                                sleep(3)
+                                autohost(webapp.config)  # this will spin the room right up again
+                                sleep(1)  # make log less annoying
+                                # if saving failed, the next iteration will fail below
+
+                    # verify server shut down
+                    try:
+                        with Client(prev_host_adr, game, "Player1") as client:
+                            assert_true(False, "Server did not shut down")
+                    except ConnectionError:
+                        pass
+
+                    for game_name in sorted(involved_games):
+                        expect_true(game_name in web_data_packages,
+                                    f"{game_name} missing from customserver data package")
+                        expect_true("item_name_groups" not in web_data_packages.get(game_name, {}),
+                                    f"item_name_groups are not supposed to be in customserver data for {game_name}")
+                        expect_true("location_name_groups" not in web_data_packages.get(game_name, {}),
+                                    f"location_name_groups are not supposed to be in customserver data for {game_name}")
+                    for game_name in web_data_packages:
+                        expect_true(game_name in involved_games,
+                                    f"Received unexpected extra data package for {game_name} from customserver")
+                    assert_equal(web_collected_items, collected_items,
+                                 "customserver did not load or save correctly during/after "
+                                 + ("Ctrl+C" if collected_items == 2 else "/exit"))
+
+                    # compare customserver to MultiServer
+                    expect_equal(local_data_packages, web_data_packages,
+                                 "customserver datapackage differs from MultiServer")
+
+            sleep(5.5)  # make sure all tasks actually stopped
+
+            # raise an exception in customserver and verify the save doesn't get destroyed
+            # local variables room is the last room's id here
+            old_data = get_multidata_for_room(webhost_client, room)
+            print(f"Destroying multidata for {room}")
+            set_multidata_for_room(webhost_client, room, bytes([0]))
+            try:
+                start_room(webhost_client, room, timeout=7)
+            except TimeoutError:
+                pass
+            else:
+                assert_true(False, "Room started with destroyed multidata")
+            print(f"Restoring multidata for {room}")
+            set_multidata_for_room(webhost_client, room, old_data)
+            with WebHostServeGame(webhost_client, room) as host:
+                with Client(host.address, game, "Player1") as client:
+                    assert_equal(len(client.checked_locations), 2,
+                                 "Save was destroyed during exception in customserver")
+                    print("Save file is not busted 🥳")
+
+        finally:
+            print("Stopping autohost")
+            stop_autohost(False)
+
+    if failure:
+        print("Some tests failed")
+        exit(1)
+    exit(0)

test/hosting/client.py

@@ -0,0 +1,110 @@
+import json
+import sys
+from typing import Any, Collection, Dict, Iterable, Optional
+from websockets import ConnectionClosed
+from websockets.sync.client import connect, ClientConnection
+from threading import Thread
+
+
+__all__ = [
+    "Client"
+]
+
+
+class Client:
+    """Incomplete, minimalistic sync test client for AP network protocol"""
+
+    recv_timeout = 1.0
+
+    host: str
+    game: str
+    slot: str
+    password: Optional[str]
+
+    _ws: Optional[ClientConnection]
+
+    games: Iterable[str]
+    data_package_checksums: Dict[str, Any]
+    games_packages: Dict[str, Any]
+    missing_locations: Collection[int]
+    checked_locations: Collection[int]
+
+    def __init__(self, host: str, game: str, slot: str, password: Optional[str] = None) -> None:
+        self.host = host
+        self.game = game
+        self.slot = slot
+        self.password = password
+        self._ws = None
+        self.games = []
+        self.data_package_checksums = {}
+        self.games_packages = {}
+        self.missing_locations = []
+        self.checked_locations = []
+
+    def __enter__(self) -> "Client":
+        try:
+            self.connect()
+        except BaseException:
+            self.__exit__(*sys.exc_info())
+            raise
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb) -> None:  # type: ignore
+        self.close()
+
+    def _poll(self) -> None:
+        assert self._ws
+        try:
+            while True:
+                self._ws.recv()
+        except (TimeoutError, ConnectionClosed, KeyboardInterrupt, SystemExit):
+            pass
+
+    def connect(self) -> None:
+        self._ws = connect(f"ws://{self.host}")
+        room_info = json.loads(self._ws.recv(self.recv_timeout))[0]
+        self.games = sorted(room_info["games"])
+        self.data_package_checksums = room_info["datapackage_checksums"]
+        self._ws.send(json.dumps([{
+            "cmd": "GetDataPackage",
+            "games": list(self.games),
+        }]))
+        data_package_msg = json.loads(self._ws.recv(self.recv_timeout))[0]
+        self.games_packages = data_package_msg["data"]["games"]
+        self._ws.send(json.dumps([{
+            "cmd": "Connect",
+            "game": self.game,
+            "name": self.slot,
+            "password": self.password,
+            "uuid": "",
+            "version": {
+                "class": "Version",
+                "major": 0,
+                "minor": 4,
+                "build": 6,
+            },
+            "items_handling": 0,
+            "tags": [],
+            "slot_data": False,
+        }]))
+        connect_result_msg = json.loads(self._ws.recv(self.recv_timeout))[0]
+        if connect_result_msg["cmd"] != "Connected":
+            raise ConnectionError(", ".join(connect_result_msg.get("errors", [connect_result_msg["cmd"]])))
+        self.missing_locations = connect_result_msg["missing_locations"]
+        self.checked_locations = connect_result_msg["checked_locations"]
+
+    def close(self) -> None:
+        if self._ws:
+            Thread(target=self._poll).start()
+            self._ws.close()
+
+    def collect(self, locations: Iterable[int]) -> None:
+        if not self._ws:
+            raise ValueError("Not connected")
+        self._ws.send(json.dumps([{
+            "cmd": "LocationChecks",
+            "locations": locations,
+        }]))
+
+    def collect_any(self) -> None:
+        self.collect([next(iter(self.missing_locations))])

test/hosting/generate.py

@@ -0,0 +1,75 @@
+import json
+import sys
+import warnings
+from pathlib import Path
+from typing import Iterable, Union, TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from multiprocessing.managers import ListProxy  # noqa
+
+__all__ = [
+    "generate_local",
+]
+
+
+def _generate_local_inner(games: Iterable[str],
+                          dest: Union[Path, str],
+                          results: "ListProxy[Union[Path, BaseException]]") -> None:
+    original_argv = sys.argv
+    warnings.simplefilter("ignore")
+    try:
+        from tempfile import TemporaryDirectory
+
+        if not isinstance(dest, Path):
+            dest = Path(dest)
+
+        with TemporaryDirectory() as players_dir:
+            with TemporaryDirectory() as output_dir:
+                import Generate
+
+                for n, game in enumerate(games, 1):
+                    player_path = Path(players_dir) / f"{n}.yaml"
+                    with open(player_path, "w", encoding="utf-8") as f:
+                        f.write(json.dumps({
+                            "name": f"Player{n}",
+                            "game": game,
+                            game: {"hard_mode": "true"},
+                            "description": f"generate_local slot {n} ('Player{n}'): {game}",
+                        }))
+
+                # this is basically copied from test/programs/test_generate.py
+                # uses a reproducible seed that is different for each set of games
+                sys.argv = [sys.argv[0], "--seed", str(hash(tuple(games))),
+                            "--player_files_path", players_dir,
+                            "--outputpath", output_dir]
+                Generate.main()
+                output_files = list(Path(output_dir).glob('*.zip'))
+                assert len(output_files) == 1
+                final_file = dest / output_files[0].name
+                output_files[0].rename(final_file)
+                results.append(final_file)
+    except BaseException as e:
+        results.append(e)
+        raise e
+    finally:
+        sys.argv = original_argv
+
+
+def generate_local(games: Iterable[str], dest: Union[Path, str]) -> Path:
+    from multiprocessing import Manager, Process, set_start_method
+
+    try:
+        set_start_method("spawn")
+    except RuntimeError:
+        pass
+
+    manager = Manager()
+    results: "ListProxy[Union[Path, Exception]]" = manager.list()
+
+    p = Process(target=_generate_local_inner, args=(games, dest, results))
+    p.start()
+    p.join()
+    result = results[0]
+    if isinstance(result, BaseException):
+        raise Exception("Could not generate multiworld") from result
+    return result

test/hosting/serve.py

@@ -0,0 +1,115 @@
+import sys
+from pathlib import Path
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from threading import Event
+    from werkzeug.test import Client as FlaskClient
+
+__all__ = [
+    "ServeGame",
+    "LocalServeGame",
+    "WebHostServeGame",
+]
+
+
+class ServeGame:
+    address: str
+
+
+def _launch_multiserver(multidata: Path, ready: "Event", stop: "Event") -> None:
+    import os
+    import warnings
+
+    original_argv = sys.argv
+    original_stdin = sys.stdin
+    warnings.simplefilter("ignore")
+    try:
+        import asyncio
+        from MultiServer import main, parse_args
+
+        sys.argv = [sys.argv[0], str(multidata), "--host", "127.0.0.1"]
+        r, w = os.pipe()
+        sys.stdin = os.fdopen(r, "r")
+
+        async def set_ready() -> None:
+            await asyncio.sleep(.01)  # switch back to other task once more
+            ready.set()  # server should be up, set ready state
+
+        async def wait_stop() -> None:
+            await asyncio.get_event_loop().run_in_executor(None, stop.wait)
+            os.fdopen(w, "w").write("/exit")
+
+        async def run() -> None:
+            # this will run main() until first await, then switch to set_ready()
+            await asyncio.gather(
+                main(parse_args()),
+                set_ready(),
+                wait_stop(),
+            )
+
+        asyncio.run(run())
+    finally:
+        sys.argv = original_argv
+        sys.stdin = original_stdin
+
+
+class LocalServeGame(ServeGame):
+    from multiprocessing import Process
+
+    _multidata: Path
+    _proc: Process
+    _stop: "Event"
+
+    def __init__(self, multidata: Path) -> None:
+        self.address = ""
+        self._multidata = multidata
+
+    def __enter__(self) -> "LocalServeGame":
+        from multiprocessing import Manager, Process, set_start_method
+
+        try:
+            set_start_method("spawn")
+        except RuntimeError:
+            pass
+
+        manager = Manager()
+        ready: "Event" = manager.Event()
+        self._stop = manager.Event()
+
+        self._proc = Process(target=_launch_multiserver, args=(self._multidata, ready, self._stop))
+        try:
+            self._proc.start()
+            ready.wait(30)
+            self.address = "localhost:38281"
+            return self
+        except BaseException:
+            self.__exit__(*sys.exc_info())
+            raise
+
+    def __exit__(self, exc_type, exc_val, exc_tb) -> None:  # type: ignore
+        try:
+            self._stop.set()
+            self._proc.join(30)
+        except TimeoutError:
+            self._proc.terminate()
+            self._proc.join()
+
+
+class WebHostServeGame(ServeGame):
+    _client: "FlaskClient"
+    _room: str
+
+    def __init__(self, app_client: "FlaskClient", room: str) -> None:
+        self.address = ""
+        self._client = app_client
+        self._room = room
+
+    def __enter__(self) -> "WebHostServeGame":
+        from .webhost import start_room
+        self.address = start_room(self._client, self._room)
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb) -> None:  # type: ignore
+        from .webhost import stop_room
+        stop_room(self._client, self._room, timeout=30)

test/hosting/webhost.py

@@ -0,0 +1,201 @@
+import re
+from pathlib import Path
+from typing import TYPE_CHECKING, Optional, cast
+
+if TYPE_CHECKING:
+    from flask import Flask
+    from werkzeug.test import Client as FlaskClient
+
+__all__ = [
+    "get_app",
+    "upload_multidata",
+    "create_room",
+    "start_room",
+    "stop_room",
+    "set_room_timeout",
+    "get_multidata_for_room",
+    "set_multidata_for_room",
+    "stop_autohost",
+]
+
+
+def get_app(tempdir: str) -> "Flask":
+    from WebHostLib import app as raw_app
+    from WebHost import get_app
+    raw_app.config["PONY"] = {
+        "provider": "sqlite",
+        "filename": str(Path(tempdir) / "host.db"),
+        "create_db": True,
+    }
+    raw_app.config.update({
+        "TESTING": True,
+        "HOST_ADDRESS": "localhost",
+        "HOSTERS": 1,
+    })
+    return get_app()
+
+
+def upload_multidata(app_client: "FlaskClient", multidata: Path) -> str:
+    response = app_client.post("/uploads", data={
+        "file": multidata.open("rb"),
+    })
+    assert response.status_code < 400, f"Upload of {multidata} failed: status {response.status_code}"
+    assert "Location" in response.headers, f"Upload of {multidata} failed: no redirect"
+    location = response.headers["Location"]
+    assert isinstance(location, str)
+    assert location.startswith("/seed/"), f"Upload of {multidata} failed: unexpected redirect"
+    return location[6:]
+
+
+def create_room(app_client: "FlaskClient", seed: str, auto_start: bool = False) -> str:
+    response = app_client.get(f"/new_room/{seed}")
+    assert response.status_code < 400, f"Creating room for {seed} failed: status {response.status_code}"
+    assert "Location" in response.headers, f"Creating room for {seed} failed: no redirect"
+    location = response.headers["Location"]
+    assert isinstance(location, str)
+    assert location.startswith("/room/"), f"Creating room for {seed} failed: unexpected redirect"
+    room_id = location[6:]
+
+    if not auto_start:
+        # by default, creating a room will auto-start it, so we update last activity here
+        stop_room(app_client, room_id, simulate_idle=False)
+
+    return room_id
+
+
+def start_room(app_client: "FlaskClient", room_id: str, timeout: float = 30) -> str:
+    from time import sleep
+
+    poll_interval = .2
+
+    print(f"Starting room {room_id}")
+    no_timeout = timeout <= 0
+    while no_timeout or timeout > 0:
+        response = app_client.get(f"/room/{room_id}")
+        assert response.status_code == 200, f"Starting room for {room_id} failed: status {response.status_code}"
+        match = re.search(r"/connect ([\w:.\-]+)", response.text)
+        if match:
+            return match[1]
+        timeout -= poll_interval
+        sleep(poll_interval)
+    raise TimeoutError("Room did not start")
+
+
+def stop_room(app_client: "FlaskClient",
+              room_id: str,
+              timeout: Optional[float] = None,
+              simulate_idle: bool = True) -> None:
+    from datetime import datetime, timedelta
+    from time import sleep
+
+    from pony.orm import db_session
+
+    from WebHostLib.models import Command, Room
+    from WebHostLib import app
+
+    poll_interval = 2
+
+    print(f"Stopping room {room_id}")
+    room_uuid = app.url_map.converters["suuid"].to_python(None, room_id)  # type: ignore[arg-type]
+
+    if timeout is not None:
+        sleep(.1)  # should not be required, but other things might use threading
+
+    with db_session:
+        room: Room = Room.get(id=room_uuid)
+        if simulate_idle:
+            new_last_activity = datetime.utcnow() - timedelta(seconds=room.timeout + 5)
+        else:
+            new_last_activity = datetime.utcnow() - timedelta(days=3)
+        room.last_activity = new_last_activity
+        address = f"localhost:{room.last_port}" if room.last_port > 0 else None
+        if address:
+            original_timeout = room.timeout
+            room.timeout = 1  # avoid spinning it up again
+            Command(room=room, commandtext="/exit")
+
+    try:
+        if address and timeout is not None:
+            print("waiting for shutdown")
+            import socket
+            host_str, port_str = tuple(address.split(":"))
+            address_tuple = host_str, int(port_str)
+
+            no_timeout = timeout <= 0
+            while no_timeout or timeout > 0:
+                s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+                try:
+                    s.connect(address_tuple)
+                    s.close()
+                except ConnectionRefusedError:
+                    return
+                sleep(poll_interval)
+                timeout -= poll_interval
+
+            raise TimeoutError("Room did not stop")
+    finally:
+        with db_session:
+            room = Room.get(id=room_uuid)
+            room.last_port = 0  # easier to detect when the host is up this way
+            if address:
+                room.timeout = original_timeout
+                room.last_activity = new_last_activity
+                print("timeout restored")
+
+
+def set_room_timeout(room_id: str, timeout: float) -> None:
+    from pony.orm import db_session
+
+    from WebHostLib.models import Room
+    from WebHostLib import app
+
+    room_uuid = app.url_map.converters["suuid"].to_python(None, room_id)  # type: ignore[arg-type]
+    with db_session:
+        room: Room = Room.get(id=room_uuid)
+        room.timeout = timeout
+
+
+def get_multidata_for_room(webhost_client: "FlaskClient", room_id: str) -> bytes:
+    from pony.orm import db_session
+
+    from WebHostLib.models import Room
+    from WebHostLib import app
+
+    room_uuid = app.url_map.converters["suuid"].to_python(None, room_id)  # type: ignore[arg-type]
+    with db_session:
+        room: Room = Room.get(id=room_uuid)
+        return cast(bytes, room.seed.multidata)
+
+
+def set_multidata_for_room(webhost_client: "FlaskClient", room_id: str, data: bytes) -> None:
+    from pony.orm import db_session
+
+    from WebHostLib.models import Room
+    from WebHostLib import app
+
+    room_uuid = app.url_map.converters["suuid"].to_python(None, room_id)  # type: ignore[arg-type]
+    with db_session:
+        room: Room = Room.get(id=room_uuid)
+        room.seed.multidata = data
+
+
+def stop_autohost(graceful: bool = True) -> None:
+    import os
+    import signal
+
+    import multiprocessing
+
+    from WebHostLib.autolauncher import stop
+
+    stop()
+    proc: multiprocessing.process.BaseProcess
+    for proc in filter(lambda child: child.name.startswith("MultiHoster"), multiprocessing.active_children()):
+        if graceful and proc.pid:
+            os.kill(proc.pid, getattr(signal, "CTRL_C_EVENT", signal.SIGINT))
+        else:
+            proc.kill()
+        try:
+            proc.join(30)
+        except TimeoutError:
+            proc.kill()
+            proc.join()

test/hosting/world.py

@@ -0,0 +1,42 @@
+import re
+import shutil
+from pathlib import Path
+from typing import Dict
+
+
+__all__ = ["copy", "delete"]
+
+
+_new_worlds: Dict[str, str] = {}
+
+
+def copy(src: str, dst: str) -> None:
+    from Utils import get_file_safe_name
+    from worlds import AutoWorldRegister
+
+    assert dst not in _new_worlds, "World already created"
+    if '"' in dst or "\\" in dst:  # easier to reject than to escape
+        raise ValueError(f"Unsupported symbols in {dst}")
+    dst_folder_name = get_file_safe_name(dst.lower())
+    src_cls = AutoWorldRegister.world_types[src]
+    src_folder = Path(src_cls.__file__).parent
+    worlds_folder = src_folder.parent
+    if (not src_cls.__file__.endswith("__init__.py") or not src_folder.is_dir()
+            or not (worlds_folder / "generic").is_dir()):
+        raise ValueError(f"Unsupported layout for copy_world from {src}")
+    dst_folder = worlds_folder / dst_folder_name
+    if dst_folder.is_dir():
+        raise ValueError(f"Destination {dst_folder} already exists")
+    shutil.copytree(src_folder, dst_folder)
+    _new_worlds[dst] = str(dst_folder)
+    with open(dst_folder / "__init__.py", "r", encoding="utf-8-sig") as f:
+        contents = f.read()
+    contents = re.sub(r'game\s*=\s*[\'"]' + re.escape(src) + r'[\'"]', f'game = "{dst}"', contents)
+    with open(dst_folder / "__init__.py", "w", encoding="utf-8") as f:
+        f.write(contents)
+
+
+def delete(name: str) -> None:
+    assert name in _new_worlds, "World not created by this script"
+    shutil.rmtree(_new_worlds[name])
+    del _new_worlds[name]