Puppet

It appears to me that undef isn’t really a real type in puppet. If I pass something that is undef to a custom function and ask Ruby for its class, it says it is a String. It almost seems like undef is just an alias for “”. It would be nice if it was a distinct type.

More importantly (see farther below), nil bubbled up from Ruby code ought to be evaluated correctly within puppet.

Let’s look at the type mappings:

define test {

$type1 = vmw_type("") # this func returns foo.class.to_s
notice("string is $type1")

$array = ["a", "b"]
$type2 = vmw_type($array)
notice("array is $type2")

$dict = { "key" => "value" }
$type3 = vmw_type($dict)
notice("dict is $type3")

$bool = true
$type5 = vmw_type($bool)
notice("true is $type5")

$undef = undef
$type4 = vmw_type($undef)
notice("undef is $type4")

}

test { “foo”: }

[rich@rich-fedora tests]$ puppet —modulepath=/Perforce /main/machines/puppet/puppetmaster/modules/ tests/vmw_type.pp notice: Scope(Test[foo]): string is String notice: Scope(Test[foo]): array is Array notice: Scope(Test[foo]): dict is Hash notice: Scope(Test[foo]): true is TrueClass notice: Scope(Test[foo]): undef is String

So either undef is really a string, or it was evaluated to a string before being passed to the custom function.

Related, when a custom function returns a nil, puppet doesn’t know what to do with it at all, and I think that nil ought to be mapped to this undef type:

[rich@rich-fedora tests]$ puppet —modulepath=/Perforce/main/machines/puppet/puppetmaster/modules/ vmw_json_parse.pp

[…]

$foo3 = vmw_json_parse("bad|,'':") # this just calls the PSON parse, returns nil if fails to parse.

$type = vmw_type($foo3)
notice("type=$type")

if $foo3 == "" { notice("foo3 is ''") }
if $foo3 == undef { notice("foo3 is undef") }
if !$foo3 { notice("foo3 is not true") }
if $foo3 { notice("foo3 is true") }

[…]

The output below shows that NilClass is not an empty string, or is it undef, but is in fact true.

notice: Scope(Test[a]): type=NilClass notice: Scope(Test[a]): foo3 is true

Now, we could have puppet walk dictionaries, arrays, and scalars returned from custom functions and transform nil scalars into “” (or undef), but it would seem smarter to change the internal guts of puppet to treat NilClass as undef (is there really any such thing as undef in the internal code? Or is it really just an alias for “”?)

So, in summary:

(a) Puppet should handle nils returned from custom functions (b) Would this be a good time to also map undef to a ruby data type, like nil?