How to fit p-dropdown inside of a table cell?

You can add min-width:100% to p-dropdown element :

<p-dropdown [style]="{'width':'100%','min-width':'100%'}" *ngSwitchCase="'invoice_status'" [options]="statuses" [autoWidth]="true"></p-dropdown>

inside the p-dropdown component there is a class .ui-dropdown this set the min-width to fixed values 12.5em; so if you set the min-width to 0 or initial will solve the problem

style.scss

.base-table { 
  p-dropdown {
    .ui-dropdown {
      min-width:0;
    }
  }
}

or like this will reset the min-width for p-dropdown component in the all project

 p-dropdown {
    .ui-dropdown {
      min-width:0; // auto , initial 😀
    }
  }

demo 🔥🔥