webhooks: Eliminate the usage of a headers.py file.

For storing HTTP headers as a function of fixture name, previously
we required that the fixture_to_headers method should reside in a
separate module called headers.py.

However, as in many cases, this method will only take a few lines,
we decided to move this function into the view.py file of the
integration instead of requiring a whole new file called headers.py

This commit introduces the small change in the system architecture,
migrates the GitHub integration, and updates the docs accordingly.

templates/zerver/api/incoming-webhooks-walkthrough.md

@@ -52,16 +52,18 @@ put key details like the event type in a separate HTTP header
 test Zulip's handling of that integration, you will need to record
 which HTTP headers are used with each fixture you capture.
 
-Since this integration-dependent, Zulip offers a simple API for doing
-this, which is probably best explained by looking at the example for
-GitHub: `zerver/webhooks/github/headers.py`; basically, as part of
-writing your integration, you'll write a special function at that path
-that maps the filename of the fixture to the set of HTTP headers to
-use. Most such functions will use the same strategy as the GitHub
-integration: encoding the third party variable header data (usually
-just an event type) in the fixture filename, in such a case, you
-won't need to explicitly write such a special function and can instead
-just use the same helper method that the GitHub integration uses.
+Since this is integration-dependent, Zulip offers a simple API for
+doing this, which is probably best explained by looking at the example
+for GitHub: `zerver/webhooks/github/view.py`; basically, as part of
+writing your integration, you'll write a special function in your
+view.py file that maps the filename of the fixture to the set of HTTP
+headers to use. This function must be named "fixture_to_headers". Most
+integrations will use the same strategy as the GitHub integration:
+encoding the third party variable header data (usually just an event
+type) in the fixture filename, in such a case, you won't need to
+explicitly write the logic for such a special function again,
+instead you can just use the same helper method that the GitHub
+integration uses.
 
 ## Step 1: Initialize your webhook python package
 

zerver/lib/webhooks/common.py

@@ -146,26 +146,16 @@ def get_fixture_http_headers(integration_name: str,
     function from the target integration module to determine what set
     of HTTP headers goes with the given test fixture.
     """
-
-    headers_module_name = "zerver.webhooks.{integration_name}.headers".format(
-        integration_name=integration_name)
+    view_module_name = "zerver.webhooks.{integration_name}.view".format(
+        integration_name=integration_name
+    )
     try:
-        # Try to import the headers.py file. If it does not exist,
-        # then that means that the integration does not have any
-        # special http headers registered.
-        #
         # TODO: We may want to migrate to a more explicit registration
         # strategy for this behavior rather than a try/except import.
-        headers_module = importlib.import_module(headers_module_name)
-    except ImportError:
+        view_module = importlib.import_module(view_module_name)
+        fixture_to_headers = view_module.fixture_to_headers  # type: ignore # we do extra exception handling in case it does not exist below.
+    except (ImportError, AttributeError):
         return {}
-    try:
-        fixture_to_headers = headers_module.fixture_to_headers  # type: ignore # we do extra exception handling in case it does not exist below.
-    except AttributeError as e:
-        msg = ". The {module_name} module must contain a fixture_to_headers method.".format(
-            module_name=headers_module_name
-        )
-        raise AttributeError(str(e) + msg)
     return fixture_to_headers(fixture_name)
 
 

zerver/tests/test_webhooks_common.py

@@ -109,12 +109,18 @@ class WebhooksCommonTestCase(ZulipTestCase):
         self.assertEqual(headers, {})
 
     @patch("zerver.lib.webhooks.common.importlib.import_module")
-    def test_get_fixture_http_headers_for_error_handling(self, import_module_mock: MagicMock) -> None:
+    def test_get_fixture_http_headers_with_no_fixtures_to_headers_function(
+        self,
+        import_module_mock: MagicMock
+    ) -> None:
+
         fake_module = SimpleNamespace()
         import_module_mock.return_value = fake_module
 
-        with self.assertRaises(AttributeError):
-            get_fixture_http_headers("some_integration", "simple_fixture")
+        self.assertEqual(
+            get_fixture_http_headers("some_integration", "simple_fixture"),
+            {}
+        )
 
     def test_standardize_headers(self) -> None:
         self.assertEqual(standardize_headers({}), {})

zerver/webhooks/github/headers.py

@@ -1,4 +0,0 @@
-from zerver.lib.webhooks.common import get_http_headers_from_filename
-
-key = "HTTP_X_GITHUB_EVENT"
-fixture_to_headers = get_http_headers_from_filename(key)

zerver/webhooks/github/view.py

@@ -16,6 +16,10 @@ from zerver.lib.webhooks.git import CONTENT_MESSAGE_TEMPLATE, \
     get_pull_request_event_message, get_push_commits_event_message, \
     get_push_tag_event_message, get_setup_webhook_message
 from zerver.models import UserProfile
+from zerver.lib.webhooks.common import \
+    get_http_headers_from_filename
+
+fixture_to_headers = get_http_headers_from_filename("HTTP_X_GITHUB_EVENT")
 
 class UnknownEventType(Exception):
     pass