As currently implemented, if, in a moment of confusion, you pass in a variable directly instead of var=foo or msg=foo, the debug module's output is less than helpful.
For instance, if I run this against a host:
---
- hosts: all
tasks:
- debug: foo
...the debug module returns:
ok: [default] => {
"msg": "Hello world!"
}
Is that the intended behavior? It seems as if it would be more helpful to, instead of printing "Hello world!", to raise an exception with a message that the user needs to specify var= or msg=.
If this change would be desirable, I'll submit a pull request for it.
-Erik