web: Fix inconsistent alternate URLs on root

Author: schneefux

web/composables/compat.ts

@@ -241,9 +241,22 @@ export function useSelfOrigin() {
 
 /** replace locale in path */
 export function getPathWithLocale(fullPath: string, locale: Locale, fallbackLocale: Locale) {
-  const urlPaths = fullPath.split('/')
+  const urlPaths = fullPath == '/' ? [''] : fullPath.split('/')
   const firstPath = urlPaths[1] as LocaleCode
   const validCodes = locales.map(l => l.code)
-  const urlWithoutLocale = validCodes.includes(firstPath) ? '/' + urlPaths.slice(2).join('/') : fullPath
-  return `${locale.iso == fallbackLocale.iso ? '' : '/' + locale.code}` + urlWithoutLocale
+  if (validCodes.includes(firstPath)) {
+    // on non-en locale
+    if (locale.iso == fallbackLocale.iso) {
+      // go to en, so remove
+      urlPaths.splice(1, 1)
+    } else {
+      // go to other, so replace
+      urlPaths[1] = locale.code
+    }
+  } else if (locale.iso != fallbackLocale.iso) {
+    // on en locale
+    // go to other, so insert
+    urlPaths.splice(1, 0, locale.code)
+  }
+  return urlPaths.join('/')
 }

web/renderer/router.ts

@@ -23,7 +23,7 @@ function createRouter(i18n: AppI18n, pageContext: PageContext, head: VueHeadClie
       link: [
         {
           rel: 'canonical',
-          href: origin + to.path, // without queries and hash
+          href: origin + (to.path == '/' ? '' : to.path), // without queries and hash
         },
         {
           rel: 'alternate',