outgoing_http: Provide a convenient way to set default headers.

zerver/lib/outgoing_http.py

@@ -5,11 +5,13 @@ from urllib3 import HTTPResponse
 
 
 class OutgoingSession(requests.Session):
-    def __init__(self, role: str, timeout: int) -> None:
+    def __init__(self, role: str, timeout: int, headers: Optional[Dict[str, str]] = None) -> None:
         super().__init__()
         outgoing_adapter = OutgoingHTTPAdapter(role=role, timeout=timeout)
         self.mount("http://", outgoing_adapter)
         self.mount("https://", outgoing_adapter)
+        if headers:
+            self.headers.update(headers)
 
 
 class OutgoingHTTPAdapter(requests.adapters.HTTPAdapter):

zerver/lib/outgoing_webhook.py

@@ -36,11 +36,7 @@ class OutgoingWebhookServiceInterface(metaclass=abc.ABCMeta):
         self.session: requests.Session = OutgoingSession(
             role="webhook",
             timeout=10,
-        )
+            headers={"User-Agent": "ZulipOutgoingWebhook/" + ZULIP_VERSION},
-        self.session.headers.update(
-            {
-                "User-Agent": "ZulipOutgoingWebhook/" + ZULIP_VERSION,
-            }
         )
 
     @abc.abstractmethod

zerver/tests/test_outgoing_http.py

@@ -48,15 +48,35 @@ class RequestMockWithTimeoutAsHeader(responses.RequestsMock):
 
 
 class TestOutgoingHttp(ZulipTestCase):
+    def test_headers(self) -> None:
+        with RequestMockWithProxySupport() as mock_requests:
+            mock_requests.add(responses.GET, "http://example.com/")
+            OutgoingSession(role="testing", timeout=1, headers={"X-Foo": "bar"}).get(
+                "http://example.com/"
+            )
+            self.assertEqual(len(mock_requests.calls), 1)
+            headers = mock_requests.calls[0].request.headers
+            # We don't see a proxy header with no proxy set
+            self.assertFalse("X-Smokescreen-Role" in headers)
+            self.assertEqual(headers["X-Foo"], "bar")
+
     @mock.patch.dict(os.environ, {"http_proxy": "http://localhost:4242"})
     def test_proxy_headers(self) -> None:
         with RequestMockWithProxySupport() as mock_requests:
             mock_requests.add(responses.GET, "http://localhost:4242/")
-            OutgoingSession(role="testing", timeout=1).get("http://example.com/")
+            OutgoingSession(role="testing", timeout=1, headers={"X-Foo": "bar"}).get(
+                "http://example.com/"
+            )
             self.assertEqual(len(mock_requests.calls), 1)
             headers = mock_requests.calls[0].request.headers
             self.assertEqual(headers["X-Smokescreen-Role"], "testing")
 
+            # We don't see the request-level headers in the proxy
+            # request.  This isn't a _true_ test because we're
+            # fiddling the headers above, instead of urllib3 actually
+            # setting them.
+            self.assertFalse("X-Foo" in headers)
+
     def test_timeouts(self) -> None:
         with RequestMockWithTimeoutAsHeader() as mock_requests:
             mock_requests.add(responses.GET, "http://example.com/")