Font size issue between input group and form control size option
Created by: ysds
The font size of .form-control in .input-group-sm is different from a single .form-control-sm when customize $input-font-size-sm or $input-btn-font-size-sm. The same is true for lg and .btn.
$input-font-size-sm: .5rem;
$input-font-size-lg: 2rem;
Demo: https://codepen.io/anon/pen/PyMyKo
One cause is related to the following lines: