css - How to span to the last column in an implicit grid?

Question

I want an item to start at the first column and end at the last column, no matter how many columns there are.

It should work like this:

item {
  grid-column-start: 1;
  grid-column-end: -1;
}

according to MDN:

Contributes the nth grid line to the grid item’s placement. If a negative integer is given, it instead counts in reverse, starting from the end edge of the explicit grid.

So this would only work on explicit grids? Why shouldn't it work on implicit grids?

Answer 1

Why shouldn't it work on implicit grids?

Because we can easily run on undefined cases¹ or a cyclic dependency. If it was the implicit grid, it means that we need to first place all the others element to identify the implicit grid then we place our element BUT if we place our element we will obtain another implicit grid so technically you cannot know the implicit grid without placing the element.

The idea behind the implicit grid is to place the element that doesn't have anything defined for their placement automatically after placing the ones with known places.

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You can overcome this by using some hacks either for row or column:

Stretch an element to the end of the automatically calculated grid, not just the explicit grid

Forcing a column to be empty in a responsive grid layout

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¹ A basic example:

.grid {
  display: grid;
  grid-template-columns: 50px;
  grid-gap: 5px;
  grid-auto-flow: column;
  grid-auto-columns:50px;
}

.grid>span {
  height: 50px;
  background: red;
}

.grid>span.place {
  grid-column: 1 / -1;
  background: blue;
}

<div class="grid">
  <span></span>
  <span class="place"></span>
</div>