Multi-site: Selected site in Vuex store is undefined

[aerni]

Bug Description

When creating/editing an entry, I need to know the currently active site to compute a value in a custom fieldtype.

I found the selected site's handle to be stored in this.$store.state.publish.base.site. The value, however, is only set when editing an existing entry. It is undefined when creating a new entry.

Maybe there's another way to get the currently selected site, that I didn't figure out yet?

How to Reproduce

1. Create a new entry and check Vuex store at state.publish.base.site. The value will be undefined.
2. Save the entry and check the value again. It will be the currently selected site.

Extra Detail

Creating a new entry:

Editing an existing entry:

Environment

Statamic version: 3.0.0-beta.43

PHP version: 7.4.6

Install method: Fresh install from statamic/statamic