Bug in Carousel for external Previous/Next buttons

[smichelotti]

Bug description:

Steps to reproduce:

1. Click "Next" button - observe nothing happens.
2. Move your mouse into the image - observe the Carousel advance on mouseenter.

Other Notes:

• If you click the Next button twice, then mouseenter the image, it will advance 2 images (corresponding exactly to number of clicks). It's correctly keeping track of active slide, but not advancing until mouse enter.
• Same behavior (in reverse) for Previous button.

Link to minimally-working StackBlitz that reproduces the issue:

StackBlitz sample that reproduces issue: https://stackblitz.com/edit/ng-bootstrap-carousel-bug

Versions of Angular, ng-bootstrap and Bootstrap:

Angular: 6.1.0

ng-bootstrap: 3.3.0

Bootstrap:

[pkozlowski-opensource]

The issue is here:

ng-bootstrap/src/carousel/carousel.ts

Line 148 in 011b488

map(() => this.interval), filter(interval => interval > 0 && this.slides.length > 0),

probably a regression introduced in e0c0050#diff-ffce1c981a98a34d71e247f67d00f7cd

[maxokorokov]

Yep it's a regression after moving carousel to OnPush, there were no tests for API calls like prev(), next() and select().

It isn't related to interval 0, same issue with any interval value → calling API methods in question wasn't switching slides immediately.