Warn a ResourceWarning when AsyncClient hasn't been closed (encode#871)

httpx/_client.py

@@ -1,5 +1,6 @@
 import functools
 import typing
+import warnings
 from types import TracebackType
 
 import httpcore
@@ -1160,6 +1161,7 @@ def __init__(
             for key, proxy in proxy_map.items()
         }
         self._proxies = dict(sorted(self._proxies.items()))
+        self._is_closed = False
 
     def _init_transport(
         self,
@@ -1627,6 +1629,7 @@ async def aclose(self) -> None:
         for proxy in self._proxies.values():
             if proxy is not None:
                 await proxy.aclose()
+        self._is_closed = True
 
     async def __aenter__(self) -> "AsyncClient":
         return self
@@ -1639,6 +1642,10 @@ async def __aexit__(
     ) -> None:
         await self.aclose()
 
+    def __del__(self) -> None:
+        if not self._is_closed:
+            warnings.warn(f"Unclosed {self!r}", ResourceWarning)
+
 
 class StreamContextManager:
     def __init__(

tests/client/test_async_client.py

@@ -166,3 +166,25 @@ async def test_100_continue(server):
 
     assert response.status_code == 200
     assert response.content == data
+
+
+@pytest.mark.usefixtures("async_environment")
+async def test_unclosed_client_caused_warning():
+    with pytest.warns(ResourceWarning):
+        client = httpx.AsyncClient()
+        del client
+
+    with pytest.warns(None) as wb:
+
+        async with httpx.AsyncClient() as client:  # noqa: F841
+            pass
+
+        assert len(wb.list) == 0
+
+
+@pytest.mark.usefixtures("async_environment")
+async def test_that_client_is_closed_after_with_block():
+    async with httpx.AsyncClient() as client:
+        pass
+
+    assert client._is_closed