Raise exception from sub-task group

src/asphalt/core/_concurrent.py

@@ -24,6 +24,9 @@
 else:
     from typing_extensions import TypeAlias
 
+if sys.version_info < (3, 11):
+    from exceptiongroup import ExceptionGroup
+
 T_Retval = TypeVar("T_Retval")
 TeardownAction: TypeAlias = Union[Callable[[], Any], Literal["cancel"], None]
 ExceptionHandler: TypeAlias = Callable[[Exception], bool]
@@ -179,10 +182,13 @@ async def wait_all_tasks_finished(self) -> None:
     async def _run(
         self, ctx: Context, resource_name: str, *, task_status: TaskStatus[None]
     ) -> None:
-        async with create_task_group() as self._task_group:
-            ctx.add_resource(self, resource_name)
-            task_status.started()
-            await self._start()
+        try:
+            async with create_task_group() as self._task_group:
+                ctx.add_resource(self, resource_name)
+                task_status.started()
+                await self._start()
+        except ExceptionGroup as excgrp:
+            raise excgrp.exceptions[0]
 
     async def _start(
         self, *, task_status: TaskStatus[None] = TASK_STATUS_IGNORED

tests/test_concurrent.py

@@ -108,13 +108,9 @@ async def taskfunc() -> NoReturn:
 
         assert len(excinfo.value.exceptions) == 1
         assert isinstance(excinfo.value.exceptions[0], ExceptionGroup)
-        excgrp0 = excinfo.value.exceptions[0]
-        assert len(excgrp0.exceptions) == 1
-        assert isinstance(excgrp0, ExceptionGroup)
-        excgrp1 = excgrp0.exceptions[0]
-        assert isinstance(excgrp1, ExceptionGroup)
-        assert len(excgrp1.exceptions) == 1
-        assert str(excgrp1.exceptions[0]) == "foo"
+        excgrp = excinfo.value.exceptions[0]
+        assert len(excgrp.exceptions) == 1
+        assert str(excgrp.exceptions[0]) == "foo"
 
     async def test_start_exception_handled(self) -> None:
         handled_exception: Exception | None = None