_vueI18n can be undefined and throw error in __DEV__

[m0ksem]

Module versions (please complete the following information):

• vue: 3.0.5
• vue-i18n: 9.1.6

Reproduction Link
https://github.com/m0ksem/vue-i18n-render-error

Look at List.vue component. It renders the Separator component from the slot, where $i18n = undefined for some reason.

Probably you need to add a simple undefined check.

Screenshots
Current behavior

Probably you should just check for undefined.

const _vueI18n: VueI18nInternal<
          Messages,
          DateTimeFormats,
          NumberFormats
        > = this.$i18n
        if (_vueI18n) {
          _vueI18n.__disableEmitter && _vueI18n.__disableEmitter()
        }
        
        delete this.$el.__VUE_I18N__
      }

in packages/vue-i18n/src/mixin.ts:133

[kazupon]

related #412
I think that issue is same!

[m0ksem]

Yes. The error message looks different, but it is the same issue.

I still get this issue. I upgraded Vue to 3.0.11 in the reproduction repo. So #412 should be reopened.

[kazupon]

I checked your repro codes and debugged your code.

I think this is bug of Vue
I have confirmed that the beforeUnmount occurs twice in your code as well.

I hope You should send an issue to vue-next along with your code.