Adds "//@Dart=2.9" on every .dart file inside /lib folder. Useful when migrating to null-safety.

add_dart_2_9.sh

# Adds "//@dart=2.9" on every .dart file inside /lib folder.
# Useful when migrating to null-safety.

addDart29ToFile() {
  echo "//@dart=2.9" > tmpfile
    cat "$1" >> tmpfile
    mv tmpfile "$1"
}

runFolderRecursively () {
  while [ "$1" ] ; do
    if [ -d "$1" ] ; then
      runFolderRecursively "$1"/*
    else
      if [[ "$1" == *.dart ]] ; then
        addDart29ToFile "$1"
      fi
    fi
    shift
  done
}

runFolderRecursively lib

@Mex978 thanks