Ensure all WSGITransport environs have a SERVER_PROTOCOL (#2708)

httpx/_transports/wsgi.py

@@ -102,6 +102,7 @@ def handle_request(self, request: Request) -> Response:
             "QUERY_STRING": request.url.query.decode("ascii"),
             "SERVER_NAME": request.url.host,
             "SERVER_PORT": str(port),
+            "SERVER_PROTOCOL": "HTTP/1.1",
             "REMOTE_ADDR": self.remote_addr,
         }
         for header_key, header_value in request.headers.raw:

tests/test_wsgi.py

@@ -173,3 +173,20 @@ def app(environ, start_response):
     assert response.status_code == 200
     assert response.text == "Hello, World!"
     assert server_port == expected_server_port
+
+
+def test_wsgi_server_protocol():
+    server_protocol = None
+
+    def app(environ, start_response):
+        nonlocal server_protocol
+        server_protocol = environ["SERVER_PROTOCOL"]
+        start_response("200 OK", [("Content-Type", "text/plain")])
+        return [b"success"]
+
+    with httpx.Client(app=app, base_url="http://testserver") as client:
+        response = client.get("/")
+
+    assert response.status_code == 200
+    assert response.text == "success"
+    assert server_protocol == "HTTP/1.1"