apps: Fix redirect from /apps -> https://zulip.com/apps/.

When this code was moved from being in zerver in 21a2fd482e, it kept
the `if ZILENCER_ENABLED` blocks.  Since ZILENCER and CORPORATE are
generally either both on or both off, the if statement became
mostly-unnecessary.

However, because tests cannot easily remove elements from
INSTALLED_APPS and re-determine URL resolution, we switch to checking
`if CORPORATE_ENABLED` as a guard, and leave these in-place.

The other side effect of this is that with e54ded49c4, most Zulip
deployments started to 404 requests for `/apps` instead of redirecting
them to `https://zulip.com/apps/` since they no longer had any path
configured for `/apps`.  Unfortunately, this URL is in widespread use
in the app (e.g. in links from the Welcome Bot), so we should ensure
that it does successfully redirect.

Add the `/apps` path to `zerver`, but only if not CORPORATE_ENABLED,
so the URLs do not overlap.

corporate/views/portico.py

@@ -23,12 +23,20 @@ from zerver.models import Realm
 
 @add_google_analytics
 def apps_view(request: HttpRequest, platform: Optional[str] = None) -> HttpResponse:
-    if settings.ZILENCER_ENABLED:
+    if not settings.CORPORATE_ENABLED:
+        # This seems impossible (CORPORATE_ENABLED set to false when
+        # rendering a "corporate" view) -- but we add it to make
+        # testing possible.  Tests default to running with the
+        # "corporate" app installed, and unsetting that is difficult,
+        # as one cannot easily reload the URL resolution -- so we add
+        # a redirect here, equivalent to the one zerver would have
+        # installed when "corporate" is not enabled, to make the
+        # behaviour testable with CORPORATE_ENABLED set to false.
+        return HttpResponseRedirect("https://zulip.com/apps/", status=301)
     return TemplateResponse(
         request,
         "corporate/apps.html",
     )
-    return HttpResponseRedirect("https://zulip.com/apps/", status=301)
 
 
 def app_download_link_redirect(request: HttpRequest, platform: str) -> HttpResponse:

zerver/context_processors.py

@@ -76,7 +76,7 @@ def get_valid_realm_from_request(request: HttpRequest) -> Realm:
 
 
 def get_apps_page_url() -> str:
-    if settings.ZILENCER_ENABLED:
+    if settings.CORPORATE_ENABLED:
         return "/apps/"
     return "https://zulip.com/apps/"
 

zerver/tests/test_docs.py

@@ -176,7 +176,6 @@ class DocPageTest(ZulipTestCase):
         self._test("/errors/5xx/", "Internal server error", landing_page=False)
 
     def test_corporate_portico_endpoints(self) -> None:
-        if settings.ZILENCER_ENABLED:
         self._test("/team/", "industry veterans")
         self._test("/apps/", "Apps for every platform.")
 
@@ -524,30 +523,38 @@ class PlansPageTest(ZulipTestCase):
 
 class AppsPageTest(ZulipTestCase):
     def test_get_apps_page_url(self) -> None:
-        with self.settings(ZILENCER_ENABLED=False):
+        with self.settings(CORPORATE_ENABLED=False):
             apps_page_url = get_apps_page_url()
         self.assertEqual(apps_page_url, "https://zulip.com/apps/")
 
-        with self.settings(ZILENCER_ENABLED=True):
+        with self.settings(CORPORATE_ENABLED=True):
             apps_page_url = get_apps_page_url()
         self.assertEqual(apps_page_url, "/apps/")
 
     def test_apps_view(self) -> None:
+        with self.settings(CORPORATE_ENABLED=False):
+            # Note that because this cannot actually uninstall the
+            # "corporate" app and trigger updates to URL resolution,
+            # this does not test the "apps/" path installed in
+            # zproject.urls, but rather the special-case for testing
+            # in corporate.views.portico
             result = self.client_get("/apps")
             self.assertEqual(result.status_code, 301)
             self.assertTrue(result["Location"].endswith("/apps/"))
 
-        with self.settings(ZILENCER_ENABLED=False):
             result = self.client_get("/apps/")
             self.assertEqual(result.status_code, 301)
             self.assertTrue(result["Location"] == "https://zulip.com/apps/")
 
-        with self.settings(ZILENCER_ENABLED=False):
             result = self.client_get("/apps/linux")
             self.assertEqual(result.status_code, 301)
             self.assertTrue(result["Location"] == "https://zulip.com/apps/")
 
-        with self.settings(ZILENCER_ENABLED=True):
+        with self.settings(CORPORATE_ENABLED=True):
+            result = self.client_get("/apps")
+            self.assertEqual(result.status_code, 301)
+            self.assertTrue(result["Location"].endswith("/apps/"))
+
             result = self.client_get("/apps/")
             self.assertEqual(result.status_code, 200)
             html = result.content.decode()

zproject/urls.py

@@ -798,6 +798,14 @@ urls += [
     path("policies/<slug:article>", policy_documentation_view),
 ]
 
+if not settings.CORPORATE_ENABLED:
+    # This conditional behavior cannot be tested directly, since
+    # urls.py is not readily reloaded in Django tests. See the block
+    # comment inside apps_view for details.
+    urls += [
+        path("apps/", RedirectView.as_view(url="https://zulip.com/apps/", permanent=True)),
+    ]
+
 # Two-factor URLs
 if settings.TWO_FACTOR_AUTHENTICATION_ENABLED:
     urls += [path("", include(tf_urls)), path("", include(tf_twilio_urls))]