Add test case

httpcore/_async/connection_pool.py

@@ -205,7 +205,7 @@ async def handle_async_request(self, request: Request) -> Response:
                 else:
                     break  # pragma: nocover
 
-        except BaseException as exc:
+        except BaseException:
             with self._optional_thread_lock:
                 # For any exception or cancellation we remove the request from
                 # the queue, and then re-assign requests to connections.
@@ -362,7 +362,7 @@ async def __aiter__(self) -> AsyncIterator[bytes]:
         try:
             async for part in self._stream:
                 yield part
-        except BaseException as exc:
+        except BaseException:
             await self.aclose()
             raise
 

httpcore/_sync/connection_pool.py

@@ -205,7 +205,7 @@ def handle_request(self, request: Request) -> Response:
                 else:
                     break  # pragma: nocover
 
-        except BaseException as exc:
+        except BaseException:
             with self._optional_thread_lock:
                 # For any exception or cancellation we remove the request from
                 # the queue, and then re-assign requests to connections.
@@ -362,7 +362,7 @@ def __iter__(self) -> Iterator[bytes]:
         try:
             for part in self._stream:
                 yield part
-        except BaseException as exc:
+        except BaseException:
             self.close()
             raise
 

tests/_async/test_connection_pool.py

@@ -410,6 +410,8 @@ async def test_connection_pool_with_connect_exception():
     be returned to the connection pool.
     """
 
+    cause_exception = Exception("cause")
+
     class FailedConnectBackend(httpcore.AsyncMockBackend):
         async def connect_tcp(
             self,
@@ -421,7 +423,7 @@ async def connect_tcp(
                 typing.Iterable[httpcore.SOCKET_OPTION]
             ] = None,
         ) -> httpcore.AsyncNetworkStream:
-            raise httpcore.ConnectError("Could not connect")
+            raise httpcore.ConnectError("Could not connect") from cause_exception
 
     network_backend = FailedConnectBackend([])
 
@@ -432,11 +434,13 @@ async def trace(name, kwargs):
 
     async with httpcore.AsyncConnectionPool(network_backend=network_backend) as pool:
         # Sending an initial request, which once complete will not return to the pool.
-        with pytest.raises(Exception):
+        with pytest.raises(Exception) as exc_info:
             await pool.request(
                 "GET", "https://example.com/", extensions={"trace": trace}
             )
 
+        assert exc_info.value.__cause__ is cause_exception
+
         info = [repr(c) for c in pool.connections]
         assert info == []
 

tests/_sync/test_connection_pool.py

@@ -410,6 +410,8 @@ def test_connection_pool_with_connect_exception():
     be returned to the connection pool.
     """
 
+    cause_exception = Exception("cause")
+
     class FailedConnectBackend(httpcore.MockBackend):
         def connect_tcp(
             self,
@@ -421,7 +423,7 @@ def connect_tcp(
                 typing.Iterable[httpcore.SOCKET_OPTION]
             ] = None,
         ) -> httpcore.NetworkStream:
-            raise httpcore.ConnectError("Could not connect")
+            raise httpcore.ConnectError("Could not connect") from cause_exception
 
     network_backend = FailedConnectBackend([])
 
@@ -432,11 +434,13 @@ def trace(name, kwargs):
 
     with httpcore.ConnectionPool(network_backend=network_backend) as pool:
         # Sending an initial request, which once complete will not return to the pool.
-        with pytest.raises(Exception):
+        with pytest.raises(Exception) as exc_info:
             pool.request(
                 "GET", "https://example.com/", extensions={"trace": trace}
             )
 
+        assert exc_info.value.__cause__ is cause_exception
+
         info = [repr(c) for c in pool.connections]
         assert info == []