What I want to achieve:
Using CSS Grid Layout, to have a page with a right column which size is derived from its content, but only up to 20% of the window width.
How I thought it would work:
div {
  border-style: solid;
}
#container {
  width: 300px;
  height: 300px;
  display: grid;
  grid-template-columns: 1fr minmax(auto, 20%);
}<div id="container">
  <div>
    some content
  </div>
  <div>
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec cursus eu leo ac ultrices. Vivamus ornare, orci sed pretium sollicitudin
  </div>
</div>It looks good, but then when I remove the content of the second div, the left column does not collapse:
div {
  border-style: solid;
}
#container {
  width: 300px;
  height: 300px;
  display: grid;
  grid-template-columns: 1fr minmax(auto, 20%);
}<div id="container">
  <div>
    some content
  </div>
  <div></div>
</div>My question:
I was under the impression that since minmax() 
(...) defines a size range greater than or equal to min and less than or equal to max.
it would mean that in my case the width is set from auto (= 0 when the div is empty) to 20%. It however stays at 20%. Why is it so?
 
     
     
     
    