Hi, there's an issue that came up recently in the 3.0RCs -- Big thanks to Erik
Dalén for reporting it in #16221 -- that involves a behaviour change to part of
the DSL. In a nutshell, this code:
define foobar ($param='Hello world') {
notice($param)
}
foobar { 'test': param => undef }
in 2.7, causes 'Hello world' in the notice. In 3.x, it's nothing. As I said in
the bug, this seems more correct to me -- I've overriden the default with an
explicit 'undef', taking off the default. The same thing goes for invoking
parameterised classes with undef arguments, which is perhaps more ambiguous
(example from matthaus):
class toplevel (
$maybe = false,
$optional = undef ) {
if ($maybe) {
class { toplevel::secondlevel: optional => undef }
}
}
In order to make use of the default for the `optional` parameter in
toplevel::secondlevel, you'd now need to either test in `toplevel` whether
`$optional` was passed into it, or have toplevel::secondlevel use an
`$optional_real` value inside it, similar to what's commonly done to append to
defaults that are array values.
The closest thing to documentation around this suggests the new behaviour is
what's intended
<http://docs.puppetlabs.com/puppet/2.7/reference/lang_classes.html#overriding-resource-attributes>:
You can remove an attribute’s previous value without setting a new one by
overriding it with the special value undef:
class base::freebsd inherits base::unix {
File['/etc/passwd'] {
group => undef,
}
}
So, I'm trying to determine whether this is a widespread pattern or an
edge-case. Do you expect 'param=>undef' to be the same as not specifying param
at all, or for the receiver to "see" the undef?
Eric Sorenson - eric.soren...@puppetlabs.com
PuppetConf'12 - 27-28 Sep in SF - http://bit.ly/pcsig12
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