Changed the scheduler API to require an explicit start call

1 files changed, 24 insertions, 11 deletions

diff --git a/src/apscheduler/schedulers/sync.py b/src/apscheduler/schedulers/sync.py
index c821a6a..d98161a 100644
--- a/src/apscheduler/schedulers/sync.py
+++ b/src/apscheduler/schedulers/sync.py
@@ -4,6 +4,7 @@ import atexit
 import os
 import platform
 import random
+import sys
 import threading
 from concurrent.futures import Future
 from contextlib import ExitStack
@@ -38,6 +39,11 @@ from ..eventbrokers.local import LocalEventBroker
 from ..marshalling import callable_to_ref
 from ..workers.sync import Worker
 
+if sys.version_info >= (3, 11):
+    from typing import Self
+else:
+    from typing_extensions import Self
+
 _microsecond_delta = timedelta(microseconds=1)
 _zero_timedelta = timedelta()
 
@@ -57,15 +63,16 @@ class Scheduler:
     _wakeup_event: threading.Event = attrs.field(init=False, factory=threading.Event)
     _wakeup_deadline: datetime | None = attrs.field(init=False, default=None)
     _services_initialized: bool = attrs.field(init=False, default=False)
-    _exit_stack: ExitStack = attrs.field(init=False, factory=ExitStack)
+    _exit_stack: ExitStack | None = attrs.field(init=False, default=None)
     _lock: threading.RLock = attrs.field(init=False, factory=threading.RLock)
 
     def __attrs_post_init__(self) -> None:
         if not self.identity:
             self.identity = f"{platform.node()}-{os.getpid()}-{id(self)}"
 
-    def __enter__(self) -> Scheduler:
-        self.start_in_background()
+    def __enter__(self: Self) -> Self:
+        self._exit_stack = ExitStack()
+        self._ensure_services_ready(self._exit_stack)
         return self
 
     def __exit__(
@@ -75,16 +82,24 @@ class Scheduler:
         exc_tb: TracebackType,
     ) -> None:
         self.stop()
-        self._join_thread()
+        self._exit_stack.__exit__(exc_type, exc_val, exc_tb)
 
     def _ensure_services_ready(self, exit_stack: ExitStack | None = None) -> None:
         """Ensure that the data store and event broker have been initialized."""
-        stack = exit_stack or self._exit_stack
         with self._lock:
             if not self._services_initialized:
+                if exit_stack is None:
+                    if self._exit_stack is None:
+                        self._exit_stack = exit_stack = ExitStack()
+                        atexit.register(self._exit_stack.close)
+                    else:
+                        exit_stack = self._exit_stack
+
                 self._services_initialized = True
+                exit_stack.callback(setattr, self, "_services_initialized", False)
+
                 self.event_broker.start()
-                stack.push(
+                exit_stack.push(
                     lambda *exc_info: self.event_broker.stop(
                         force=exc_info[0] is not None
                     )
@@ -92,13 +107,11 @@ class Scheduler:
 
                 # Initialize the data store
                 self.data_store.start(self.event_broker)
-                stack.push(
+                exit_stack.push(
                     lambda *exc_info: self.data_store.stop(
                         force=exc_info[0] is not None
                     )
                 )
-                if not exit_stack:
-                    atexit.register(self._exit_stack.close)
 
     def _schedule_added_or_modified(self, event: Event) -> None:
         event_ = cast("ScheduleAdded | ScheduleUpdated", event)
@@ -377,8 +390,8 @@ class Scheduler:
             self._thread = None
             raise
 
-        atexit.register(self._join_thread)
-        atexit.register(self.stop)
+        self._exit_stack.callback(self._join_thread)
+        self._exit_stack.callback(self.stop)
 
     def stop(self) -> None:
         """