bash: Cancelling the execution of 'trap handler DEBUG'

Question

I can get a function myHandler() to execute before a bash command by doing the following:

function myHandler() {
   ...
}
trap 'myHandler' DEBUG

However, I'd like to be able to proceed with or abort the execution of the impending BASH_COMMAND based on a runtime condition within myHandler as follows:

function myHandler() {
   if ! myCondition ; then
      abort the execution of BASH_COMMAND right here
   fi
   # Proceed with the execution of BASH_COMMAND
}

Is this possible?

Answer 1

You can, just enable extdebug and return a non-zero code (See the description of extdebug option) from myHandler:

$ function myHandler() {
  if [[ $SKIP = "true" ]]; then return 1; fi;
  echo 'myHandler execute'
}
$ trap 'myHandler' DEBUG
$ shopt -s extdebug
$ echo 1
myHandler execute
1
$ SKIP=true
myHandler execute
$ echo 1