bug: inconsistent redirects and locale detection

[tafelnl]

Environment

• Node Version: v16.14.2
• Nuxt Version: 3.2.0
• Nitro Version: 2.2.1
• Builder: vite
• User Config: ssr, modules, i18n, typescript
• Runtime Modules: @nuxtjs/[email protected]
• Build Modules: -

Reproduction

https://stackblitz.com/edit/github-8hn8cb

Describe the bug

I think there's quite some inconsistencies/unclarity in this plugin regarding redirection and locale detection.

---

For the rest of this issue, suppose we have the following base config set:

  i18n: {
    locales: [
      {
        code: 'en',
        name: 'English',
        iso: 'en-GB',
      },
      {
        code: 'nl',
        name: 'Nederlands',
        iso: 'nl-NL',
      },
    ],
    defaultLocale: 'en',
  },

---

A few examples:

---

1.

with the following settings:

  i18n: {
    // ... base config ...
    strategy: 'prefix',
  },

If your browser locale is set to nl and you navigate to /, the following will happen:

• the logs will detect nl is your browser locale
• not redirected anywhere (stays on /) [1]
• ends with a 302 Found status code [2]
• locale wrongly set to en instead of nl [3]
• cookie wrongly set to en instead of nl [4]

[1] although from the docs I understand the prefix strategy should redirect to the correct locale.
[2] which is not good for SEO and just in general unexpected I guess
[3] I don't know why this would happen
[4] I don't understand when a cookie will be or will not be set (see example 2. also)

---

2.

with the following settings:

  i18n: {
    // ... base config ...
    detectBrowserLanguage: {
      alwaysRedirect: true,
    },
    strategy: 'prefix',
  },

If your browser locale is set to nl and you navigate to /, the following will happen:

• the logs will detect nl is your browser locale
• not redirected anywhere (stays on /) [1]
• ends with a 302 Found status code [2]
• locale correctly set to nl
• no cookie will be set [5]

[5] Weird because in the previous example, it was set (incorrectly, but that doesn't matter here for now). So I think it's unexpected to not set it here.

---

3.

with the following settings:

  i18n: {
    // ... base config ...
    detectBrowserLanguage: {
      alwaysRedirect: true,
      redirectOn: 'no prefix',
    },
    strategy: 'prefix',
  },

If your browser locale is set to nl and you navigate to /foobar, the following will happen:

• the logs will detect nl is your browser locale
• not redirected anywhere (stays on /foobar) [1]
• ends with a 302 Found status code [2]
• locale wrongly set to en instead of nl [6]
• cookie wrongly set to en instead of nl [4]

[6] Which is weird, because as we saw in the previous example, for the root it was correctly set to nl

Additional context

Maybe these examples should have been split up into separate issues. But I'm not sure if they are or are not related to each other.

Logs

No response

[Suniron]

Same error with nuxt bridge

[ashour]

I've encountered similar behaviour