Arrayformula get value of cell above if condition meets

I need to get the value of the cell above if a condition is met in an arrayformula as I need it to expand automatically when a new row is added

In excel I would use a table with a function looking something like:

In B2: =IF(A2="",A1,A2)

In google sheets I do not know how to achieve this:

In B2: =ARRAYFORMULA(IF(Row(A:A)="","",ROW(A:A)-1))

I thought that ROW(A:A)-1 would subtract 1 from the current row number and give me the result. But that did not work.

Thank you in advance for any suggestions.