findDOMNode is deprecated in StrictMode.

findDOMNode is deprecated in StrictMode but trigger still uses it.
react version: 16.9.0.

Using findDOMNode will cause below Warning:

Warning: findDOMNode is deprecated in StrictMode. findDOMNode was passed an instance of Wave which is inside StrictMode. Instead, add a ref directly to the element you want to reference. Learn more about using refs safely here: https://fb.me/react-strict-mode-find-node
    in button (created by Button)
    in Wave (created by Button)
    in Button (created by Trigger)
    in Trigger (created by ForwardRef(Tooltip))
    in ForwardRef(Tooltip) (created by Tooltip)
    in Tooltip (created by Popover)
   ...

まず、警告に示されている Trigger、Tooltip、Button、Wave のパスをたどって、findDOMNode が使われている場所を特定します。次に、React 16.9.0 と StrictMode で警告を再現し、その後、trigger の動作が変わらないまま警告が消えていることを確認します。