JSFiddle - React, Tailwind, and code Playground

HTML

<div class="row">
    <div class="col">input auto 100% of the free width space</div>
    <button type="submit">button<br> auto of the<br> inner content</button>
</div>

CSS

.row {
    display: table;
    /* table-layout: fixed; */
    /* width: 100%; */
}

.col,
button {
    display: table-cell;
    padding: 8px 12px;
    outline: 1px dashed red;
}