catching exceptions in _queue_consumer meta task

setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = asyncio-taskpool
-version = 0.7.0
+version = 0.7.1
 author = Daniil Fajnberg
 author_email = mail@daniil.fajnberg.de
 description = Dynamically manage pools of asyncio tasks
@@ -9,7 +9,7 @@ long_description_content_type = text/markdown
 keywords = asyncio, concurrency, tasks, coroutines, asynchronous, server
 url = https://git.fajnberg.de/daniil/asyncio-taskpool
 project_urls =
-    Bug Tracker = https://git.fajnberg.de/daniil/asyncio-taskpool/issues
+    Bug Tracker = https://github.com/daniil-berg/asyncio-taskpool/issues
 classifiers =
     Development Status :: 3 - Alpha
     Programming Language :: Python :: 3

src/asyncio_taskpool/pool.py

@@ -775,8 +775,15 @@ class TaskPool(BaseTaskPool):
                 if next_arg is self._QUEUE_END_SENTINEL:
                     # The `_queue_producer()` either reached the last argument or was cancelled.
                     return
-                await self._start_task(star_function(func, next_arg, arg_stars=arg_stars), group_name=group_name,
+                try:
-                                       ignore_lock=True, end_callback=release_cb, cancel_callback=cancel_callback)
+                    await self._start_task(star_function(func, next_arg, arg_stars=arg_stars), group_name=group_name,
+                                           ignore_lock=True, end_callback=release_cb, cancel_callback=cancel_callback)
+                except Exception as e:
+                    # This means an exception occurred during task **creation**, meaning no task has been created.
+                    # It does not imply an error within the task itself.
+                    log.exception("%s occurred while trying to create task: %s(%s%s)",
+                                  str(e.__class__.__name__), func.__name__, '*' * arg_stars, str(next_arg))
+                    map_semaphore.release()
 
     async def _map(self, group_name: str, group_size: int, func: CoroutineFunc, arg_iter: ArgsT, arg_stars: int,
                    end_callback: EndCB = None, cancel_callback: CancelCB = None) -> None:

tests/test_pool.py

@@ -603,28 +603,34 @@ class TaskPoolTestCase(CommonTestCase):
 
     @patch.object(pool, 'star_function')
     @patch.object(pool.TaskPool, '_start_task')
-    @patch.object(pool, 'Semaphore')
     @patch.object(pool.TaskPool, '_get_map_end_callback')
-    async def test__queue_consumer(self, mock__get_map_end_callback: MagicMock, mock_semaphore_cls: MagicMock,
+    @patch.object(pool, 'Semaphore')
+    async def test__queue_consumer(self, mock_semaphore_cls: MagicMock, mock__get_map_end_callback: MagicMock,
                                    mock__start_task: AsyncMock, mock_star_function: MagicMock):
-        mock__get_map_end_callback.return_value = map_cb = MagicMock()
         mock_semaphore_cls.return_value = semaphore = Semaphore(3)
-        mock_star_function.return_value = awaitable = 'totally an awaitable'
+        mock__get_map_end_callback.return_value = map_cb = MagicMock()
-        arg1, arg2 = 123456789, 'function argument'
+        awaitable = 'totally an awaitable'
+        mock_star_function.side_effect = [awaitable, awaitable, Exception()]
+        arg1, arg2, bad = 123456789, 'function argument', None
         mock_q_maxsize = 3
-        mock_q = MagicMock(__aenter__=AsyncMock(side_effect=[arg1, arg2, pool.TaskPool._QUEUE_END_SENTINEL]),
+        mock_q = MagicMock(__aenter__=AsyncMock(side_effect=[arg1, arg2, bad, pool.TaskPool._QUEUE_END_SENTINEL]),
                            __aexit__=AsyncMock(), maxsize=mock_q_maxsize)
-        group_name, mock_func, stars = 'whatever', MagicMock(), 3
+        group_name, mock_func, stars = 'whatever', MagicMock(__name__="mock"), 3
         end_cb, cancel_cb = MagicMock(), MagicMock()
         self.assertIsNone(await self.task_pool._queue_consumer(mock_q, group_name, mock_func, stars, end_cb, cancel_cb))
+        # We expect the semaphore to be acquired 3 times, then be released once after the exception occurs, then
+        # acquired once more when the `_QUEUE_END_SENTINEL` is reached. Since we initialized it with a value of 3,
+        # at the end of the loop, we expect it be locked.
         self.assertTrue(semaphore.locked())
+        mock_semaphore_cls.assert_called_once_with(mock_q_maxsize)
         mock__get_map_end_callback.assert_called_once_with(semaphore, actual_end_callback=end_cb)
         mock__start_task.assert_has_awaits(2 * [
             call(awaitable, group_name=group_name, ignore_lock=True, end_callback=map_cb, cancel_callback=cancel_cb)
         ])
         mock_star_function.assert_has_calls([
             call(mock_func, arg1, arg_stars=stars),
-            call(mock_func, arg2, arg_stars=stars)
+            call(mock_func, arg2, arg_stars=stars),
+            call(mock_func, bad, arg_stars=stars)
         ])
 
     @patch.object(pool, 'create_task')