This is essentially the behavior of stdlib pick function.
$required_var = pick(hiera("var_a"), hiera("var_b"))
Which could be improved to allow a custom error message:
https://github.com/puppetlabs/puppetlabs-stdlib/blob/master/lib/puppet/parser/functions/pick.rb#L24
Nan
On Wed, Oct 16, 2013 at 10:48 AM, Spencer Krum <[email protected]>wrote:
> I've developed the following pattern. Please don't hate.
>
> [nibz@pdxudev01 sandbox]$ cat testpuppetfailtemplate.sh
>
> $bar = 'lies'
>
> $derp=inline_template("<%= @bar || scope.function_fail(['die']) %>")
> notify { $derp: }
>
> Which produces:
>
> [nibz@pdxudev01 sandbox]$ puppet apply testpuppetfailtemplate.sh
> Notice: lies
> Notice: /Stage[main]//Notify[lies]/message: defined 'message' as 'lies'
> Notice: Finished catalog run in 0.09 seconds
>
> Then commenting out $bar
>
> [nibz@pdxudev01 sandbox]$ puppet apply testpuppetfailtemplate.sh
> Error: Failed to parse inline template: die at
> /home/nibz/sandbox/testpuppetfailtemplate.sh:4 on node
> pdxudev01.devtst.go2uti.com
> Error: Failed to parse inline template: die at
> /home/nibz/sandbox/testpuppetfailtemplate.sh:4 on node
> pdxudev01.devtst.go2uti.com
>
> :)
>
>
>
> On Wednesday, July 17, 2013 8:29:07 AM UTC-7, jcbollinger wrote:
>>
>>
>>
>> On Monday, July 15, 2013 11:25:50 AM UTC-5, Brano Zarnovican wrote:
>>>
>>> Hi,
>>>
>>> I have the following code snippet
>>>
>>> node default {
>>> # $var_a .. is undefined
>>> $var_b = hiera("var_b", undef)
>>> $var_c = undef
>>>
>>> file { "/var/tmp/foo.txt": content => inline_template("
>>>
>>> <% if @var_a %>
>>> var_b = <%= @var_a %>
>>> <% else %>
>>> <% info(\"var_a is undefined\") %>
>>> <% end -%>
>>>
>>> <% if @var_b %>
>>> var_b = <%= @var_b %>
>>> <% else %>
>>> <% info(\"var_b is undefined\") %>
>>> <% end -%>
>>>
>>> <% if @var_c %>
>>> var_c = <%= @var_c %>
>>> <% else %>
>>> <% info(\"var_c is undefined\") %>
>>> <% end -%>
>>>
>>> "
>>> ), }
>>> }
>>>
>>> Applying it, will generate these two info messages.
>>>
>>> Info: template[inline]: var_a is undefined
>>> Info: template[inline]: var_c is undefined
>>> var_b =
>>>
>>> What I would like puppet to do is to fail if template is referencing a
>>> variable which is not defined, without having to wrap it with
>>> if-else-fail()-end.
>>>
>>> Another strange thing I've noticed that "undef" behaves differently if
>>> it is a default value for hiera lookup (see var_b vs var_c).
>>>
>>> Actually, my code looks more like..
>>>
>>> $var_a = hiera("var_a")
>>> $var_b = hiera("var_b")
>>> $var_c = hiera("var_c")
>>> file {"..": content => template(hiera("tmpl_name")) }
>>>
>>> That will fail if any variable a,b,c is undefined in hiera, no matter if
>>> it is used in template or not. I can rewrite it to
>>>
>>> $var_a = hiera("var_a", undef)
>>> $var_b = hiera("var_b", undef)
>>> $var_c = hiera("var_c", undef)
>>> file {"..": content => template(hiera("tmpl_name")) }
>>>
>>> This will not fail even if variable used by the template is undefined.
>>> The value is quietly replaced by empty string.
>>>
>>> In other words, I would like to delay the failure from hiera() lookup to
>>> the time when it is actually used in template. Can it be done without
>>> explicitly testing it with "if" inside template ?
>>>
>>> Thanks,
>>>
>>> BranoZ
>>>
>>> PS: we are (or soon be) on puppet 3.2.
>>>
>>>
>>
>> You have a couple of separate issues here, but first a little background
>> to make sure we're on the same page: templates are evaluated by the master,
>> not by agents, so the only form of failure a template can exhibit is to
>> interrupt catalog compilation with a synthetic parse error. It cannot
>> cause application of the associated resource to fail on the agent.
>>
>> With that said, a template can call Puppet function via the 'scope'
>> object available to it. In particular, if you want a template evaluation
>> to fail as I describe, then it can invoke the fail() function:
>>
>> <% scope.function_fail('variable foo is not set') %>
>>
>>
>> Now, as a separate matter, you are correct that hiera will translate the
>> default value 'undef' to an empty string. It will never return an undef
>> value (I'm not sure that even makes sense). A common approach is to
>> instead choose a default value that you are confident will not appear as a
>> valid value in your data. One conventional choice is 'NOTSET'. Your code
>> then tests for that special value instead of (or in addition to) testing
>> whether the variable is defined.
>>
>>
>> John
>>
>> --
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