How to easily test/experiment with jinja templating in ansible?

[Dario Bertini]

I've been bitten one too many times by the way that ansible interacts with jinja. I'd say its error handling is a little bit too lax, defaulting to return empty strings or similar things that then end up getting my playbooks to fail later down the line.

To prevent that, I know that I can have a better look at the available vars and facts gathered with the setup module

ansible -m setup

but often I'd like to see how I can use these with jinja: I'd like to have a REPL for it (or failing that, a shorter feedback loop)

debug tasks inside a playbook are not ideal also because I cannot use them to debug issues with templates used before tasks execution (e.g. to define a variable)

I was thinking of simply using

ansible -m debug -a "msg={{the_jinja_expression_I_want_to_test}}"

but I realized that the output is not quite what I'd expect:

ansible -m debug -a "msg={{hostvars[inventory_hostname]}}"

for example returns

kalivm | success >> {
    "msg": "{'ansible_ssh_host':"                                                                                                   
}

and

ansible -m debug -a "msg={{hostvars}}"

prints

kalivm | success >> {
    "msg": "{'kalivm':"                                                                                                             
}

It seems to be a truncated json string, probably because not all the variables have yet been made available there in a simple ansible module invocation (they'd probably be available in a full playbook run)

Is this known behavior? How do you usually handle these things?                                                                                                                              

Thanks

[Azul Inho]

I usually attach a debugger,
http://michaeldehaan.net/post/35403909347/tips-on-using-debuggers-with-ansible

or set a small template action to dump the contents of the dictionary/variable whatever to a local file on my box.
It's easier to inspect it that way,

[Marc Tamsky]

On Friday, December 19, 2014 at 7:50:09 AM UTC-8, Dario Bertini wrote:

I was thinking of simply using

ansible -m debug -a "msg={{the_jinja_expression_I_want_to_test}}"

but I realized that the output is not quite what I'd expect:

ansible -m debug -a "msg={{hostvars[inventory_hostname]}}"

ansible -m debug -a "msg={{hostvars}}"

I agree it's not totally obvious.

The answer at http://serverfault.com/a/695798 helped me figure out that it needed to be quoted.

quote your test expressions and you get the output you expected:

# ansible --version

ansible 1.9.6

  configured module search path = None

# ansible -m debug -a msg="'{{hostvars[inventory_hostname]}}'"

localhost | success >> {

    "msg": "{'inventory_hostname': '127.0.0.1', 'group_names': ['ungrouped'], 'inventory_hostname_short': '127'}"

}

[Azul]

and 2 years later ...

: )

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