Revert "Turn scope["client"] to None on TestClient (#2377)"

This reverts commit 483849a.

starlette/testclient.py

@@ -298,7 +298,7 @@ def handle_request(self, request: httpx.Request) -> httpx.Response:
                 "scheme": scheme,
                 "query_string": query.encode(),
                 "headers": headers,
-                "client": None,
+                "client": ["testclient", 50000],
                 "server": [host, port],
                 "subprotocols": subprotocols,
                 "state": self.app_state.copy(),
@@ -317,7 +317,7 @@ def handle_request(self, request: httpx.Request) -> httpx.Response:
             "scheme": scheme,
             "query_string": query.encode(),
             "headers": headers,
-            "client": None,
+            "client": ["testclient", 50000],
             "server": [host, port],
             "extensions": {"http.response.debug": {}},
             "state": self.app_state.copy(),

tests/test_testclient.py

@@ -274,6 +274,20 @@ async def asgi(receive: Receive, send: Send) -> None:
     assert websocket.should_close.is_set()
 
 
+
+def test_client(test_client_factory):
+    async def app(scope, receive, send):
+        client = scope.get("client")
+        assert client is not None
+        host, port = client
+        response = JSONResponse({"host": host, "port": port})
+        await response(scope, receive, send)
+
+    client = test_client_factory(app)
+    response = client.get("/")
+    assert response.json() == {"host": "testclient", "port": 50000}
+
+
 @pytest.mark.parametrize("param", ("2020-07-14T00:00:00+00:00", "España", "voilà"))
 def test_query_params(test_client_factory: TestClientFactory, param: str) -> None:
     def homepage(request: Request) -> Response: