`packer console` fails to evaluate functions

command packer console fails to evaluate functions, it just echo inputs back.

[root@ip-10-1-2-37 packer_tutorial]# packer console

regex_replace(timestamp(), “[- TZ:]”, “”)
regex_replace(timestamp(), “[- TZ:]”, “”)
^c

But if we append a template to the command, then it works as expected, why?

[root@ip-10-1-2-37 packer_tutorial]# packer console ./aws-ubuntu.pkr.hcl

regex_replace(timestamp(), “[- TZ:]”, “”)
20221021002816
^C
[root@ip-10-1-2-37 packer_tutorial]#