Save stacktraces in context manager and print on error

PFERD/utils.py

@@ -2,6 +2,7 @@ import asyncio
 import getpass
 import sys
 import threading
+import traceback
 from abc import ABC, abstractmethod
 from collections.abc import Callable
 from contextlib import AsyncExitStack
@@ -114,13 +115,23 @@ class ReusableAsyncContextManager(ABC, Generic[T]):
     def __init__(self) -> None:
         self._active = False
         self._stack = AsyncExitStack()
+        self._create_stacktrace = traceback.format_stack()
+        self._enter_stacktraces = []
 
     @abstractmethod
     async def _on_aenter(self) -> T:
         pass
 
     async def __aenter__(self) -> T:
+        self._enter_stacktraces.append(traceback.format_stack())
+
         if self._active:
+            print("Context manager was already active. Created at:")
+            print("".join(self._create_stacktrace))
+            print("\n== Previous __aenter__ calls")
+            for i, stacktrace in enumerate(self._enter_stacktraces, start=1):
+                print(f"\n-- __aenter__ call #{i} at:")
+                print("".join(stacktrace))
             raise RuntimeError("Nested or otherwise concurrent usage is not allowed")
 
         self._active = True
@@ -144,6 +155,8 @@ class ReusableAsyncContextManager(ABC, Generic[T]):
         if not self._active:
             raise RuntimeError("__aexit__ called too many times")
 
+        self._enter_stacktraces.pop()
+
         result = await self._stack.__aexit__(exc_type, exc_value, traceback)
         self._active = False
         return result