Popover2 backdrop animated appearance doesn't work

[sashaglobenko]

Environment

• 3.47.0
• mac os
• Chrome 92.0.4515.131

Code Sandbox

https://codesandbox.io/s/blueprint-sandbox-forked-w6qej?file=/src/Popover2Example.tsx

Steps to reproduce

1. Click button

Actual behavior

Backdrop appears without any animation like when open Dialog.

Expected behavior

Backdrop appears with fade animation

[adidahiya]

Are you trying to add a custom popover backdrop CSS transition?

1. Why?
2. This should be doable, but you'll need to get a little more specific / in the weeds with the TransitionGroup classes... you probably need to attach a custom class to your backdrop and then target it with .my-popover-backdrop.bp3-popover2-enter { ... } (see CSSTransition docs)