doc/starlight: add route middleware to fix edit link

doc/starlight/astro.config.mjs

@@ -177,6 +177,7 @@ export default defineConfig({
         replacesTitle: true,
       },
       plugins: [starlightImageZoom()],
+      routeMiddleware: "./src/routeData.ts",
       editLink: {
         baseUrl: "https://github.com/RIOT-OS/RIOT/tree/master/doc/guides",
       },

doc/starlight/src/routeData.ts

@@ -0,0 +1,23 @@
+import { defineRouteMiddleware } from "@astrojs/starlight/route-data";
+
+/**
+ * Since we currently use a symlink to comply with the (broken)
+ * docs folder scanning of starlight, this will break the edit
+ * link since, while technically correct, our symlink will be
+ * shown as github.com/RIOT-OS/RIOT/doc/guides/src/content/docs/foobar
+ * Since github can't parse symlinks, we need to modify the editUrl
+ * through a route middleware in order for the edit link to still function
+ *
+ * As soon as base directory changes get fixed, this should be removed
+ * again! See: https://github.com/withastro/starlight/pull/3332
+ */
+export const onRequest = defineRouteMiddleware((context) => {
+  const { starlightRoute } = context.locals;
+
+  if (starlightRoute.editUrl) {
+    starlightRoute.editUrl = new URL(
+      starlightRoute.editUrl.href.replace("src/content/docs/", ""),
+      starlightRoute.editUrl,
+    );
+  }
+});