Consult nested mocks innermost-first on the httpx backend

newsfragments/3544.change

@@ -0,0 +1 @@
+Fix nested ``MockVWS`` instances on the ``httpx`` backend: an inner mock is now the only one which answers while it is running, matching the ``requests`` and ``httpx2`` backends. Previously the outer mock kept answering and requests to the inner mock's URL were refused.

src/mock_vws/_respx_mock_server/decorators.py

@@ -7,6 +7,7 @@
 
 import httpx
 import respx
+from respx.mocks import Mocker
 
 from mock_vws._mock_common import RequestData, Route
 
@@ -183,4 +184,20 @@ def start_respx_router(
         router.route().mock(side_effect=_block_unmatched)
 
     router.start()
+
+    # ``respx`` keeps every started router in a single process-wide list and
+    # tries them in the order they were started, so an outer mock would
+    # answer requests which an inner, more recently started, mock was created
+    # for. The catch-all route above means the outer mock always answers, so
+    # the inner one would never be consulted at all.
+    #
+    # Moving the newest router to the front of that list makes nested mocks
+    # resolve innermost-first, matching the ``requests`` and ``httpx2``
+    # backends, whose patches form a LIFO stack. ``respx.Router.start``
+    # looks its mocker up by name, and this router is created with the
+    # default name, so the lookup cannot fail.
+    mocker = Mocker.registry[router.using or ""]
+    mocker.routers.remove(router)
+    mocker.routers.insert(0, router)
+
     return router

tests/mock_vws/test_respx_mock_usage.py

@@ -124,6 +124,31 @@ def test_add_get_and_delete_target(
             with pytest.raises(expected_exception=UnknownTargetError):
                 client.get_target_record(target_id=target_id)
 
+    @staticmethod
+    def test_nested_mocks() -> None:
+        """A mock inside another mock leaves the outer one working.
+
+        The innermost mock is the only one which answers while it is
+        running, which is what the ``requests`` and ``httpx2`` backends do
+        too, and the outer mock answers again once the inner one has
+        stopped.
+        """
+        outer_url = "https://vws.vuforia.com/summary"
+        inner_url = "https://vuforia.vws.example.com/summary"
+
+        with MockVWS():
+            with MockVWS(base_vws_url="https://vuforia.vws.example.com"):
+                inner_response = httpx.get(url=inner_url, timeout=30)
+                with pytest.raises(expected_exception=httpx.ConnectError):
+                    httpx.get(url=outer_url, timeout=30)
+            outer_response = httpx.get(url=outer_url, timeout=30)
+
+            with pytest.raises(expected_exception=httpx.ConnectError):
+                httpx.get(url=inner_url, timeout=30)
+
+        assert inner_response.status_code == HTTPStatus.UNAUTHORIZED
+        assert outer_response.status_code == HTTPStatus.UNAUTHORIZED
+
 
 class TestCloudRecoService:
     """Synchronous cloud query usage through the mock via ``httpx``."""