Better handling for progress bar with max=0

[devoto13]

Bug description:

Currently progress bar with the max value of 0 fills for the width necessary for the label to display. This is not consistent behavior and it will be better to make max=0 a special case and always fill either 0% or 100%.

I think 100% will be a more sensible behavior because of cases like value=42 and max=0. In this case progress bar will trim value to 0, but 100% will make some sense in this situation unlike 0%.

Link to minimally-working StackBlitz that reproduces the issue:

https://stackblitz.com/edit/angular-mc1mw9

Versions of Angular, ng-bootstrap and Bootstrap:

Angular: 8.2.0

ng-bootstrap: 5.1.0

Bootstrap: 4.3.1

[maxokorokov]

Currently progress bar with the max value of 0 fills for the width necessary for the label to display

Well, from what I see style="width: ..." is not set at all when max === 0 → this looks like a bug and should be fixed. Works fine for negative values.

[devoto13]

The real question is what value should be displayed in this case.
It may be as well worth throwing the error when max=0 as a not intended usage of the component.

[maxokorokov]

I don't think it should fail with an error, it should just render the component correctly.

What's wrong with having max === 0? When max is 0, you just can't go beyond 0. Looks pretty consistent to me.

This issue from my point of view is that:

[value]="10" [max]="0" [showValue]="true"

Gives:

• NaN instead of 0
• doesn't apply style="width:..."

Let's discuss changing default behaviour in #3390

[maxokorokov]

Also should update the docs, saying that max SHOULD be a positive value

[maxokorokov]

Ok, on reflection and playing with standard <progress>, I think we should do same thing it does and fallback max to default value which is 100 in bootstrap.

Left a comment in the review: #3400 (review)