From 94f81980726aa85a1183d1d2b42b92ed31b3f1bc Mon Sep 17 00:00:00 2001
From: Shubham Padia <shubham@zulip.com>
Date: Tue, 23 Sep 2025 14:23:06 +0000
Subject: [PATCH] help: Redirect web app URLs to web app proxy port.

Help center dev server always runs on a port different than the web
app. We have relative URLs pointing to the web app in the help
center, but they are not on the port help center is running on. We
redirect instead to our web app proxy port.
---
 starlight_help/astro.config.mjs | 19 +++++++++++++++++--
 tools/run-dev                   |  4 ++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/starlight_help/astro.config.mjs b/starlight_help/astro.config.mjs
index d19f6b1b25..2dbe98744d 100644
--- a/starlight_help/astro.config.mjs
+++ b/starlight_help/astro.config.mjs
@@ -11,6 +11,7 @@ import Icons from "unplugin-icons/vite";
  * @returns {import("vite").PluginOption}
  */
 function createRedirectPlugin() {
+    const proxyPort = process.env.ZULIP_WEB_APP_PROXY_PORT || "9991";
     // Astro and starlight middlewares run after astro's vite middleware,
     // which gives error before our logic here could run, so the only option
     // left with us was to use a vite plugin.
@@ -33,10 +34,10 @@ function createRedirectPlugin() {
                     route: "",
                     /**
                      * @param {import("http").IncomingMessage} req
-                     * @param {import("http").ServerResponse} _res
+                     * @param {import("http").ServerResponse} res
                      * @param {Function} next
                      */
-                    handle(req, _res, next) {
+                    handle(req, res, next) {
                         // Canonical URL for the root of the help center is /help/,
                         // but for all other help URLs, there should be no trailingSlash.
                         // We have set trailingSlash to never in astro. Setting it to ignore
@@ -46,6 +47,20 @@ function createRedirectPlugin() {
                         if (req.url === "/help/") {
                             req.url = "/help";
                         }
+
+                        // Help center dev server always runs on a port different than
+                        // the web app. We have relative URLs pointing to the web app
+                        // in the help center, but they are not on the port help center
+                        // is running on. We redirect here to our web app proxy port.
+                        if (req.url && !req.url.startsWith("/help")) {
+                            const host = req.headers.host || "localhost";
+                            const redirectUrl = new URL(req.url, `http://${host}`);
+                            redirectUrl.port = proxyPort;
+                            res.writeHead(302, {Location: redirectUrl.toString()});
+                            res.end();
+                            return;
+                        }
+
                         next();
                     },
                 });
diff --git a/tools/run-dev b/tools/run-dev
index 44a472024e..934fd77791 100755
--- a/tools/run-dev
+++ b/tools/run-dev
@@ -306,6 +306,9 @@ async def forward(upstream_port: int, request: web.Request) -> web.StreamRespons
 def run_help_center_dev_server(
     external_host: str, port: int = help_center_port
 ) -> "subprocess.Popen[bytes]":
+    env = os.environ.copy()
+    env["ZULIP_WEB_APP_PROXY_PORT"] = str(proxy_port)
+
     return subprocess.Popen(
         [
             "/usr/local/bin/corepack",
@@ -316,6 +319,7 @@ def run_help_center_dev_server(
             f"--allowed-hosts={urlsplit(external_host).hostname}",
         ],
         cwd="starlight_help",
+        env=env,
     )