Warn when using SEO features without configuring baseUrl

[dargmuesli]

Environment

• Operating System: Linux
• Node Version: v18.18.0
• Nuxt Version: 3.11.2
• CLI Version: 3.11.1
• Nitro Version: 2.9.6
• Package Manager: npm@10.2.3
• Builder: -
• User Config: modules, devtools, i18n
• Runtime Modules: @nuxtjs/i18n@8.3.1
• Build Modules: -

Reproduction

https://stackblitz.com/edit/bobbiegoede-nuxt-i18n-starter-4wdrme?file=app.vue

Describe the bug

Starting with v8.3.1 some trailing slashes disappeared, which leads to these invalid headers when using useLocaleHead({ addSeoAttributes: true }):

Notice the empty hrefs, which should include / as they did before.

Additional context

No response

Logs

No response

[BobbieGoede]

After looking into this again, you actually need to set a baseUrl (see https://i18n.nuxtjs.org/docs/guide/seo) since relative URLs for alternate links are not considered valid (according to Google https://developers.google.com/search/docs/specialty/international/localized-versions#all-method-guidelines).

We should probably add warnings if baseUrl is unset when using addSeoAttributes and perhaps disable the tags altogether if unset (in v9, as that would be breaking)

[dargmuesli]

You're right! I was just setting baseUrl in the runtimeConfig for $production, which was a mistake by me. Thank you for looking into this! A warning sounds like a great idea. If you want, you can rename this issue to fit the idea of adding a warning, or close this and create a new issue of course.