From 593f7b0723d757dc312a1f778ae1925c19d75448 Mon Sep 17 00:00:00 2001
From: Claas Augner <495429+caugner@users.noreply.github.com>
Date: Wed, 10 Jul 2024 10:44:03 +0200
Subject: [PATCH] fix(cloud-function): avoid double slash where canonical url
 has trailing slash (#11441)

Avoids redirecting `curriculum/index.json` to `curriculum//index.json`.
---
 .../middlewares/redirect-non-canonicals.ts    | 20 ++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/cloud-function/src/middlewares/redirect-non-canonicals.ts b/cloud-function/src/middlewares/redirect-non-canonicals.ts
index a2abc9514822..0c8f1d3eb1b3 100644
--- a/cloud-function/src/middlewares/redirect-non-canonicals.ts
+++ b/cloud-function/src/middlewares/redirect-non-canonicals.ts
@@ -34,13 +34,23 @@ export async function redirectNonCanonicals(
       typeof REDIRECTS[source] == "string" &&
       REDIRECTS[source] !== originalSource
     ) {
-      const target = REDIRECTS[source] + suffix + parsedUrl.search;
-      return redirect(res, target, {
-        status: 301,
-        cacheControlSeconds: THIRTY_DAYS,
-      });
+      const target = joinPath(REDIRECTS[source], suffix) + parsedUrl.search;
+      if (pathname !== target) {
+        return redirect(res, target, {
+          status: 301,
+          cacheControlSeconds: THIRTY_DAYS,
+        });
+      }
     }
   }
 
   next();
 }
+
+function joinPath(a: string, b: string) {
+  if (a.endsWith("/") && b.startsWith("/")) {
+    return a + b.slice(1);
+  } else {
+    return a + b;
+  }
+}