Dynamic table columns are not reactive

[GMartigny]

Overview of the problem

Buefy version: v0.9.20
Vuejs version: v2.6.14
OS/Browser: any

Description

When I build a table with dynamic columns, changing the columns count don't refresh the view. What I mean by "dynamic columns" is having columns as an array and looping over b-table-column with a v-for.

Steps to reproduce

1. Have a b-table
2. Set an array in a computed
3. Define b-table-column that loop over the array
4. Change the array length
5. Observe that the number of columns hasn't change

Expected behavior

It should be reactive and refresh accordingly. It might be due to the way cells are keyed.

Actual behavior

The columns are updated, but not the column count.

Playground

[jtommy]

I think to understand the problem