Puppet users - Jan 2013 - Extending a standard type

I''m trying to extend the standard ''user'' type to add
maintenance of some of
the contents of a user''s home directory, and I''m trying to
avoid creating
an entirely new custom type if I can.  The approach I''m taking is to
create
a site::user defined type which in turns calls the standard user type. 
I''m
having a problem figuring out how to manage the optional parameters.  

The most likely path seems to be something like this (simplified for 
example):

define site::user (
        $comment,
        $ensure,
        $home,
        $name = $title,
        $password,
    ) {

    user { "$title":
        comment => $comment,
        ensure => $ensure,
        home => $home,
        name => $name,
        password => $password,
    }
}

The problem with this, of course, is that the parameters to site::user 
aren''t optional, and I''d like them to be.  I''ve tried
setting their
defaults to null strings, but I get errors about reassigning variables if I 
do that.  

Of course, this would be even better.. but doesn''t appear to be a valid
syntax in puppet:

define site::user ( $**args ) {
   user { "$title":
      $args
   }
}

This seems to me to be the sort of thing that''d be in a puppet
cookbook,
but google hasn''t shown me any useful docs or examples for what
I''m trying
to do.  Does this approach even make sense, or is there a better way?

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On Saturday, January 26, 2013 6:55:57 PM UTC-6, Matthew Pounsett
wrote:
>
> I''m trying to extend the standard ''user'' type to
add maintenance of some
> of the contents of a user''s home directory, and I''m
trying to avoid
> creating an entirely new custom type if I can.  The approach I''m
taking is
> to create a site::user defined type which in turns calls the standard user 
> type.


That''s a good and widely-used approach.

 
>  I''m having a problem figuring out how to manage the optional
parameters.
>
> The most likely path seems to be something like this (simplified for 
> example):
>
> define site::user (
>         $comment,
>         $ensure,
>         $home,
>         $name = $title,
>

Don''t do that ($name = $title).  Puppet provides it automatically (both
the
parameter and the default).

Moreover, I am uncertain whether it is safe anyway to use $title as a 
resource default.  It certainly *isn''t* safe to use explicit resource 
properties, regardless of the order in which they are listed.

 
>         $password,
>     ) {
>
>     user { "$title":
>         comment => $comment,
>         ensure => $ensure,
>         home => $home,
>         name => $name,
>         password => $password,
>     }
> }
>
> The problem with this, of course, is that the parameters to site::user 
> aren''t optional, and I''d like them to be.  I''ve
tried setting their
> defaults to null strings, but I get errors about reassigning variables if I
> do that.
>

The usual paradigm is this:

define mymodule::foo ( $param1 = ''NOTSET'' ) {
  $real_param1 = $param1 ? {
    ''NOTSET'' => <some-appropriate-value-maybe-undef>,
    default => $param1
  }
  sometype { $name:
    param => $real_param1
  }
}

Yes, it''s a bit clunky, but it works.
 

> Of course, this would be even better.. but doesn''t appear to be a
valid
> syntax in puppet:
>
> define site::user ( $**args ) {
>    user { "$title":
>       $args
>    }
> }
>
>
No, Puppet doesn''t have anything like that.  The closest would probably
be
the create_resources() function, which you can read about in the docs.

 
> This seems to me to be the sort of thing that''d be in a puppet
cookbook,
> but google hasn''t shown me any useful docs or examples for what
I''m trying
> to do.  Does this approach even make sense, or is there a better way?
>

I''m surprised you didn''t find an example like the one above. 
It appears
all over the place, not least in the archives of this group.

Also, have you read the official Puppet DSL docs (at 
http://docs.puppetlabs.com/puppet/3/reference/)?  They don''t answer
your
particular question, but they would have told you about $name, and they 
have a lot of other useful information.


John

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On Monday, 28 January 2013 11:14:59 UTC-5, jcbollinger wrote:
 
> define site::user (
>>         $comment,
>>         $ensure,
>>         $home,
>>         $name = $title,
>>
>
>
> Don''t do that ($name = $title).  Puppet provides it automatically
(both
> the parameter and the default).
>
In this case, $name is the login name of the user being created .. it''s
a
valid parameter of the ''user'' resource type.  I''m not
sure how I''m supposed
to do not use it.  I have read the Puppet reference manual.. but not for 
puppet 3, since I''m not using that.  

 
> Moreover, I am uncertain whether it is safe anyway to use $title as a 
> resource default.  It certainly *isn''t* safe to use explicit
resource
> properties, regardless of the order in which they are listed.

I''n not sure what you mean by that.  Using $title as a default is
widely
used (see namevar) .. I''m not sure what you mean about explicit
resource
properties.

> The usual paradigm is this:
> define mymodule::foo ( $param1 = ''NOTSET'' ) {
>   $real_param1 = $param1 ? {
>     ''NOTSET'' =>
<some-appropriate-value-maybe-undef>,
>     default => $param1
>   }
>   sometype { $name:
>     param => $real_param1
>   }
> }
> Yes, it''s a bit clunky, but it works.
 

This is great if I want to set my own defaults, but I don''t.  The
''user''
resource already has its own way of handling unspecified parameters, and I 
don''t want to override those unless absolutely necessary.   I think the
above would require me to re-implement a bunch of its defaults logic, which 
would be especially problematic for things like ''gid''.  

 
> No, Puppet doesn''t have anything like that.  The closest would
probably be
> the create_resources() function, which you can read about in the docs.

I''ll have a look.. maybe there''s some way I can make use of
it.
 
> I''m surprised you didn''t find an example like the one
above.  It appears
> all over the place, not least in the archives of this group.
>
Also, have you read the official Puppet DSL docs (at 
> http://docs.puppetlabs.com/puppet/3/reference/)?  They don''t
answer your
> particular question, but they would have told you about $name, and they 
> have a lot of other useful information.

The only occurrence of the string "name" in the DSL doc at that
location is
as a placeholder... and it applies to ruby, not puppet manifests.  I
don''t
see anything there about use of $name inside a puppet class.


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You can set the default values to undef and then the standard user type
will use its defaults (if any).  It usually makes sense to default the
ensure parameter to ''present'' though because if it is undef
then nothing
will happen:

define site::user (
        $ensure     = ''present'',
        $comment = undef,
        $home       = undef,
        $password = undef,
    ) {
    user { $title:
        ensure     => $ensure,
        comment => $comment,
        home       => $home,
        password => $password,
    }
    ...
}

Note that $name and $title are the same thing so you probably shouldn''t
specify a value for $name.

  - Keith


On 27 January 2013 00:55, Matthew Pounsett <matt.pounsett@gmail.com>
wrote:
> I''m trying to extend the standard ''user'' type to
add maintenance of some
> of the contents of a user''s home directory, and I''m
trying to avoid
> creating an entirely new custom type if I can.  The approach I''m
taking is
> to create a site::user defined type which in turns calls the standard user
> type.  I''m having a problem figuring out how to manage the
optional
> parameters.
>
> The most likely path seems to be something like this (simplified for
> example):
>
> define site::user (
>         $comment,
>         $ensure,
>         $home,
>         $name = $title,
>         $password,
>     ) {
>
>     user { "$title":
>         comment => $comment,
>         ensure => $ensure,
>         home => $home,
>         name => $name,
>         password => $password,
>     }
> }
>
> The problem with this, of course, is that the parameters to site::user
> aren''t optional, and I''d like them to be.  I''ve
tried setting their
> defaults to null strings, but I get errors about reassigning variables if I
> do that.
>
> Of course, this would be even better.. but doesn''t appear to be a
valid
> syntax in puppet:
>
> define site::user ( $**args ) {
>    user { "$title":
>       $args
>    }
> }
>
> This seems to me to be the sort of thing that''d be in a puppet
cookbook,
> but google hasn''t shown me any useful docs or examples for what
I''m trying
> to do.  Does this approach even make sense, or is there a better way?
>
> --
> You received this message because you are subscribed to the Google Groups
> "Puppet Users" group.
> To post to this group, send email to puppet-users@googlegroups.com.
> To unsubscribe from this group, send email to
> puppet-users+unsubscribe@googlegroups.com.
> Visit this group at http://groups.google.com/group/puppet-users?hl=en.
> For more options, visit https://groups.google.com/groups/opt_out.
>
>
>
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On Monday, January 28, 2013 11:07:51 AM UTC-6, Matthew Pounsett
wrote:
>
>
>
> On Monday, 28 January 2013 11:14:59 UTC-5, jcbollinger wrote:
>  
>
>> define site::user (
>>>         $comment,
>>>         $ensure,
>>>         $home,
>>>         $name = $title,
>>>
>>
>>
>> Don''t do that ($name = $title).  Puppet provides it
automatically (both
>> the parameter and the default).
>>
>
> In this case, $name is the login name of the user being created ..
it''s a
> valid parameter of the ''user'' resource type. 
I''m not sure how I''m supposed
> to do not use it.  I have read the Puppet reference manual.. but not for 
> puppet 3, since I''m not using that.  
>

You are missing the point: Puppet automatically endows every defined type 
with a $name parameter, and automatically defaults its value to the 
$title.  See 
http://docs.puppetlabs.com/puppet/3/reference/lang_defined_types.html#title-and-name.
Though Puppet might not complain, it is at best poor form to declare the 
same thing explicitly.

 
>
>  
>
>> Moreover, I am uncertain whether it is safe anyway to use $title as a 
>> resource default.  It certainly *isn''t* safe to use explicit
resource
>> properties, regardless of the order in which they are listed.
>
>
> I''n not sure what you mean by that.  Using $title as a default is
widely
> used (see namevar) .. I''m not sure what you mean about explicit
resource
> properties.
>

I answer my own question: the automatic $title and $name parameters are 
documented safe to use as parameter defaults (but I''m not sure whether 
$name remains safe if you (re)declare it explicitly).  No (other) 
parameters you explicitly define are safe for use as default values of 
other parameters.  That is, you must not do this:

site::user ( $uid, $gid = $uid ) {
# ...
}

 
>
>
>> The usual paradigm is this:
>> define mymodule::foo ( $param1 = ''NOTSET'' ) {
>>   $real_param1 = $param1 ? {
>>     ''NOTSET'' =>
<some-appropriate-value-maybe-undef>,
>>     default => $param1
>>   }
>>   sometype { $name:
>>     param => $real_param1
>>   }
>> }
>> Yes, it''s a bit clunky, but it works.
>
>  
>
> This is great if I want to set my own defaults, but I don''t.  The
''user''
> resource already has its own way of handling unspecified parameters, and I 
> don''t want to override those unless absolutely necessary.   I
think the
> above would require me to re-implement a bunch of its defaults logic, which
> would be especially problematic for things like ''gid''.  
>

Note the "maybe-undef" in <some-appropriate-value-maybe-undef>. 
I''m
referring there to the literal keyword ''undef'', which should
serve your
needs.  In this case you can also use ''undef'' directly as the
default, as
Keith suggested, but that does not allow you to distinguish between the 
case where the user doesn''t set a parameter and the one where he
explicitly
sets it to undef.  You may not need that distinction now, but if you 
continue writing Puppet manifests then one day you will.

 
>
>  
>
>> No, Puppet doesn''t have anything like that.  The closest would
probably
>> be the create_resources() function, which you can read about in the
docs.
>
>
> I''ll have a look.. maybe there''s some way I can make use
of it.
>  
>
>> I''m surprised you didn''t find an example like the one
above.  It appears
>> all over the place, not least in the archives of this group.
>>
> Also, have you read the official Puppet DSL docs (at 
>> http://docs.puppetlabs.com/puppet/3/reference/)?  They don''t
answer your
>> particular question, but they would have told you about $name, and they
>> have a lot of other useful information.
>
>
> The only occurrence of the string "name" in the DSL doc at that
location
> is as a placeholder... and it applies to ruby, not puppet manifests.  I 
> don''t see anything there about use of $name inside a puppet class.
>
>
You''re not talking about a class, you''re talking about a
definition.  The
distinction is important.  Anyway, I gave a direct link above to the docs 
for $name and $title in defined types.


John

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On Tuesday, 29 January 2013 00:29:43 UTC-5, Keith Burdis
wrote:
>
> You can set the default values to undef and then the standard user type 
> will use its defaults (if any).  It usually makes sense to default the 
> ensure parameter to ''present'' though because if it is
undef then nothing
> will happen:
>
Ah, I see... I''d tried using empty strings, but for some reason undef
never
occurred to me.  Thanks, it looks like this will work perfectly.

>
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