On Tue, Aug 5, 2014 at 8:18 AM, Erik Dalén <erik.gustav.da...@gmail.com>
wrote:
> On 5 August 2014 16:25, Reid Vandewiele <r...@puppetlabs.com> wrote:
>
>> On Mon, Aug 4, 2014 at 3:18 PM, Henrik Lindberg <
>> henrik.lindb...@cloudsmith.com> wrote:
>>
>>>
>>> So, to summarize: The use of * => as an operator is not liked but the
>>> concept of being able to set attributes from a hash is. Unfortunately, it
>>> is not possible to directly allow an expression at the position in
>>> question, there must be a syntactical marker.
>>>
>>> As pointed out earlier, the * => was thought to read as "any_attribute
>>> => from_these_values", but I totally grok if people have an allergic
>>> reaction.
>>>
>>> We can do this though:
>>>
>>> file { default: ($hash) }
>>>
>>> This works because it is impossible to have an attribute name in
>>> parentheses.
>>>
>>> In use:
>>>
>>> file (
>>> default : ($my_file_defaults + { mode => '0666' });
>>> '/tmp/foo': ;
>>> '/tmp/bar': ;
>>> }
>>>
>>> Is that better? No new operator, but you have to use parentheses around
>>> the expression.
>>>
>>> We can naturally also revert the functionality, but it seems it is liked
>>> conceptually.
>>>
>>>
>>> - henrik
>>>
>>
>>
>> I think the parenthesis are far preferable over *=>. That isn't to say I
>> like them - I don't particularly. But the functionality is desirable, and
>> if it's a matter of a technical limitation then parenthesis are a Good
>> Enough (TM) compromise from the more ideal direct use of a hash.
>>
>
> I really prefer the use of * => over the parenthesis. Especially if you
> need to merge things into the hash. For example look at this example:
>
> # using parenthesis hash style
> class foo (
> $servername = $::fqdn,
>
> $port = 80,
>
> $ssl = false,
> $extra_opts={},
> ) {
> apache::vhost { $servername: ($extra_opts + {
> port => $port,
>
> ssl => $ssl,
> })
> }
> }
>
>
> # using * =>
> class foo (
> $servername = $::fqdn,
>
> $port = 80,
>
> $ssl = false,
> $extra_opts={},
> ) {
> apache::vhost { $servername:
> port => $port,
>
> ssl => $ssl,
> * => $extra_opts,
> }
>
> }
>
>
The behavior that we worked out doesn't allow having the splat along with
the other parameters, the reason being that it isn't clear what is meant by
that. You had in your head that port and ssl are overridden by extra_opts
(possibly because they come first?), but another, completely reasonable
interpretation is that it is the other way around (port and ssl override
extra_opts because they are explicitly given. In order to remove any of
that confusion the current specification and implementation doesn't allow
mixing. That can, I think, be changed.
In the current implementation this would need to be:
apache::vhost { $servername:
* => $extra_opts + { port => $port, ssl => $ssl }
}
> IMO the *=> is way more readable (as gist here if formatting is screwed up
> for you: https://gist.github.com/dalen/57b37b80a9ba1879b78c). This is
> quite similar to what I linked earlier that I am doing in
> https://github.com/spotify/puppet-puppetexplorer/blob/master/manifests/init.pp#L89-L97
> So it is not just a contrived example.
>
>
My argument against using parenthesis is that parenthesis, are often read
as "seldom necessary grouping". I believe that most programmers read them
as usually only needed for fixing precedence problems, which is really what
is happening here but it doesn't look like it. Based on that I can imagine
that a common, and frustrating mistake would be:
apache::vhost { $servername: $opts }
And then confusion and anger and bug reports.
> --
> Erik Dalén
>
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