help: Add default page to display on /help when help server is off.

We've copied the button and error colors from portico_signin.css. We did
not want the new HTML file to depend on portico_signin.css since they
are unrelated. In addition, having those colors diverge over time might
not be an issue.

We make the raw mode work with /help and /help/ both.

See https://chat.zulip.org/#narrow/channel/19-documentation/topic/edits.20not.20appearing.20with.20vagrant/near/2257442

Co-authored-by: Alya Abbott <alya@zulip.com>

zerver/tests/test_docs.py

@@ -48,6 +48,7 @@ class DocPageTest(ZulipTestCase):
             "/devtools/",
             "/emails/",
             "/errors/",
+            "/help",
             "/integrations/",
         ]:
             if url.startswith(prefix):
@@ -70,6 +71,11 @@ class DocPageTest(ZulipTestCase):
         if url.startswith("/attribution/"):
             allow_robots = False
 
+        # When a raw MDX file is being fetched, the meta tag to
+        # disallow robots will be absent.
+        if url in ["/help/status-and-availability?raw", "/help/?raw", "/help?raw"]:
+            allow_robots = True
+
         result = self.get_doc(url, subdomain=subdomain)
         self.print_msg_if_error(url, result)
         self.assertEqual(result.status_code, 200)
@@ -243,6 +249,49 @@ class DocPageTest(ZulipTestCase):
         self._test("/devtools/", ["Useful development URLs"])
         self._test("/emails/", ["Manually generate most emails"])
 
+    def test_dev_help_default_page_endpoints(self) -> None:
+        # View on Zulip.com and View source URLs should be visible.
+        self._test(
+            "/help/status-and-availability",
+            [
+                'href="https://zulip.com/help/status-and-availability"',
+                'href="/help/status-and-availability?raw"',
+            ],
+        )
+
+        # Raw MDX file should be shown when `?raw` is present.
+        self._test(
+            "/help/status-and-availability?raw",
+            ["---", "title: Status and availability", "### Set a status"],
+        )
+
+        self._test(
+            "/help/nonexistent-page-that-does-not-exist",
+            ["This is not a valid help path and not a valid MDX file"],
+        )
+
+        # `?raw` should have no effect when the page does not exist
+        self._test(
+            "/help/nonexistent-page-that-does-not-exist?raw",
+            ["This is not a valid help path and not a valid MDX file"],
+        )
+
+        # Root /help and /help/ is a special case without subpath.
+        self._test("/help/?raw", ["---", "title: Zulip help center"])
+        self._test("/help?raw", ["---", "title: Zulip help center"])
+
+        with (
+            mock.patch("builtins.open", side_effect=OSError("File read error")),
+            self.assertLogs("django.request", level="ERROR") as m,
+        ):
+            result = self.client_get("/help/status-and-availability?raw")
+            self.assertEqual(result.status_code, 500)
+            self.assertIn("Error reading MDX file", result.content.decode())
+            self.assertEqual(
+                m.output,
+                ["ERROR:django.request:Internal Server Error: /help/status-and-availability"],
+            )
+
     def test_error_endpoints(self) -> None:
         self._test("/errors/404/", ["Page not found"])
         self._test("/errors/5xx/", ["Internal server error"])

zerver/views/development/help.py

@@ -0,0 +1,57 @@
+import os
+
+import werkzeug
+from django.conf import settings
+from django.http import HttpRequest, HttpResponse
+from django.shortcuts import render
+
+
+def help_dev_mode_view(request: HttpRequest, subpath: str = "") -> HttpResponse:
+    """
+    Dev only view that displays help information for setting up the
+    help center dev server in the default `run-dev` mode where the
+    help center server is not running. Also serves raw MDX content when
+    `raw` query param is passed is passed.
+    """
+
+    def read_mdx_file(filename: str) -> HttpResponse:
+        file_path = os.path.join(
+            settings.DEPLOY_ROOT, "starlight_help", "src", "content", "docs", f"{filename}.mdx"
+        )
+        try:
+            with open(file_path, encoding="utf-8") as f:
+                content = f.read()
+            return HttpResponse(content, content_type="text/plain")
+        except OSError:
+            return HttpResponse("Error reading MDX file", status=500)
+
+    mdx_file_exists = False
+    is_requesting_raw_file = request.GET.get("raw") == ""
+
+    if subpath:
+        subpath = werkzeug.utils.secure_filename(subpath)
+        raw_url = f"/help/{subpath}?raw"
+        mdx_path = os.path.join(
+            settings.DEPLOY_ROOT, "starlight_help", "src", "content", "docs", f"{subpath}.mdx"
+        )
+        mdx_file_exists = os.path.exists(mdx_path) and "/include/" not in mdx_path
+        if mdx_file_exists and is_requesting_raw_file:
+            return read_mdx_file(subpath)
+    else:
+        if request.path.endswith("/"):
+            raw_url = "/help/?raw"
+        else:
+            raw_url = "/help?raw"
+        mdx_file_exists = True
+        if is_requesting_raw_file:
+            return read_mdx_file("index")
+
+    return render(
+        request,
+        "zerver/development/dev_help.html",
+        {
+            "subpath": subpath,
+            "mdx_file_exists": mdx_file_exists,
+            "raw_url": raw_url,
+        },
+    )