JCU/fix(ssr): serve a reloaded comcol search tab from the page it belongs to

Opening a community or collection moves the address bar to its /search tab, and #1424 put that
path in ssr.excludePathPatterns. Reloading there returned the 1113-byte CSR shell, so the visitor
got a white page for 0.6s on a fast desktop and up to 3.4s on a slow one.

Both URLs render ComcolSearchSectionComponent and the comcol page itself is server-rendered, so a
GET for the bare tab URL is redirected to it; the client puts /search back in the address bar as
it did before. A URL carrying a query is left alone, which is the point of the exclusion: what
saturated SSR on mendelu (#1402) is the Discovery facet parameter space, and those URLs all carry
f. parameters. The redirect turns itself off if the tab stops being excluded, or if the comcol
page ever becomes excluded.

Doing this in ComcolPageBrowseByComponent instead, by not redirecting to the default tab, looks
tidier and does not work: getSearchLink() returns currentPath(router) for an in-place search, so
every facet link would move to /collections/<uuid>?f. , which no pattern matches, and the trap
reopens.

Also fixes the robots.txt comment claiming the SSR-side rule is not configured, wrong since #1424.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: milanmajchrak

server.ts

@@ -221,10 +221,43 @@ export function app() {
   return server;
 }
 
+/**
+ * A community or collection moves the address bar to its /search tab as soon as the client boots,
+ * and that path is in ssr.excludePathPatterns, so a reload there returns the empty CSR shell. Both
+ * URLs render the same ComcolSearchSectionComponent, so a bare reload is sent back to the page
+ * itself, which is server-rendered; the client puts /search back in the address bar.
+ *
+ * Only for a URL with no query: /search?f.author=... keeps its query and stays excluded, which is
+ * what the exclusion is there for.
+ *
+ * @param req current request
+ * @returns the path to redirect to, or null to handle the request normally
+ */
+function comcolSearchTabRedirect(req): string {
+  if (!environment.ssr.enabled || req.method !== 'GET' || req.originalUrl.includes('?')) {
+    return null;
+  }
+  const match = /^(\/(?:collections|communities)\/[0-9a-f-]{36})\/search\/?$/i.exec(req.path);
+  if (match === null) {
+    return null;
+  }
+  const patterns = environment.ssr.excludePathPatterns;
+  // Nothing to gain when the tab is server-rendered anyway, or when the page itself is not.
+  if (!isExcludedFromSsr(req.path, patterns) || isExcludedFromSsr(match[1], patterns)) {
+    return null;
+  }
+  return req.baseUrl + match[1];
+}
+
 /*
  * The callback function to serve server side angular
  */
 function ngApp(req, res, next) {
+  const comcolPath = comcolSearchTabRedirect(req);
+  if (comcolPath !== null) {
+    res.redirect(302, comcolPath);
+    return;
+  }
   if (environment.ssr.enabled && req.method === 'GET' && (req.path === '/' || !isExcludedFromSsr(req.path, environment.ssr.excludePathPatterns))) {
     // Render the page to user via SSR (server side rendering)
     serverSideRender(req, res, next);

src/robots.txt.ejs

@@ -31,7 +31,7 @@ Disallow: /communities/*/search
 Disallow: /*?f.
 Disallow: /*&f.
 # NOTE: robots.txt is advisory only; it does not stop crawlers that ignore it.
-# The SSR-side enforcement (ssr.excludePathPatterns) is not configured here.
+# ssr.excludePathPatterns in config.yml enforces the facet part server-side, for any user agent.
 
 # Heavy Discovery facet queries on browse pages
 Disallow: /collections/*?f