Clicking the cleared autocomplete input field should show the dropdown list.
After clearing the autocomplete field using a clear button that sets the input value to null or '', clicking the cleared input field will not show the dropdown list. The dropdown list will show if the user clicks the label above the input field, clicks very close to the top side of the input line, or clicks away from the input then back into the input field.
https://stackblitz.com/edit/angular-srhd19?embed=1&file=app/autocomplete-simple-example.html

Angular6, Material 6.4.7 and 7.2.0, Windows 7 and Linux, Firefox 60.5.2, Chrome 72.0.3626.121
The user can enter a character or select up or down arrows to force the dropdown list to open after input has been cleared.
It works if $event.stopPropagation() is added after the variable is set to null
https://angular-material-autocomplete-clear.stackblitz.io
@lnu
Thanks, using $event.stopPropagation() worked for me.
(click)="inputProcess = null ; $event.stopPropagation() "
Most helpful comment
It works if
$event.stopPropagation()is added after the variable is set to nullhttps://angular-material-autocomplete-clear.stackblitz.io