Puppet users - Aug 2012 - The rewritten Puppet 2.7 language reference is live

Hi all,

I''ve finished the all new Puppet 2.7 language reference. EXCITING!
Well,
exciting to me, at least. Table of contents:

http://docs.puppetlabs.com/puppet/2.7/reference/

Visual index (for when you know what you''re looking for but you
don''t know
what it''s called):

http://docs.puppetlabs.com/puppet/2.7/reference/lang_visual_index.html

And of course, use the navigation in the left sidebar to jump between 
pages. 

Our goal here is to nail down every detail of how the Puppet language 
works, then cut new versions along with major Puppet releases. We''ll 
eventually be expanding this versioned document with non-language details 
-- we''ve been referring to this plan as the "Puppet reference
manual." Its
purpose isn''t to replace any of the guides or how-tos, but to lay down
a
"just the facts" baseline that lets you get in and out fast. 

Anyway, we hope you find it useful. Thanks for using Puppet. 

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it''s very useful,i think it''s better than puppet guide,

2012/8/22 Nick Fagerlund <nick.fagerlund@puppetlabs.com>
> Hi all,
>
> I''ve finished the all new Puppet 2.7 language reference. EXCITING!
Well,
> exciting to me, at least. Table of contents:
>
> http://docs.puppetlabs.com/puppet/2.7/reference/
>
> Visual index (for when you know what you''re looking for but you
don''t know
> what it''s called):
>
> http://docs.puppetlabs.com/puppet/2.7/reference/lang_visual_index.html
>
> And of course, use the navigation in the left sidebar to jump between
> pages.
>
> Our goal here is to nail down every detail of how the Puppet language
> works, then cut new versions along with major Puppet releases.
We''ll
> eventually be expanding this versioned document with non-language details
> -- we''ve been referring to this plan as the "Puppet reference
manual." Its
> purpose isn''t to replace any of the guides or how-tos, but to lay
down a
> "just the facts" baseline that lets you get in and out fast.
>
> Anyway, we hope you find it useful. Thanks for using Puppet.
>
>  --
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Very nice!

But I''m wondering about the section on "Reserved Variable
Names" that
says that reusing fact names as variables in a local scope may cause
malfunctions. This is something I''ve done quite a lot without any
problem, is it considered unsupported and might break in future
versions?
The only issue is of course that you hide the fact in the local scope
so you get for example $::ipaddress and $ipaddress with different
values.

But with a defined type that has a ipaddress parameter it doesn''t
really make much sense to name it anything else. And besides you can
never know what facts a system might have installed.

On 21 August 2012 22:40, Nick Fagerlund <nick.fagerlund@puppetlabs.com>
wrote:
> Hi all,
>
> I''ve finished the all new Puppet 2.7 language reference. EXCITING!
Well,
> exciting to me, at least. Table of contents:
>
> http://docs.puppetlabs.com/puppet/2.7/reference/
>
> Visual index (for when you know what you''re looking for but you
don''t know
> what it''s called):
>
> http://docs.puppetlabs.com/puppet/2.7/reference/lang_visual_index.html
>
> And of course, use the navigation in the left sidebar to jump between
pages.
>
> Our goal here is to nail down every detail of how the Puppet language
works,
> then cut new versions along with major Puppet releases. We''ll
eventually be
> expanding this versioned document with non-language details --
we''ve been
> referring to this plan as the "Puppet reference manual." Its
purpose isn''t
> to replace any of the guides or how-tos, but to lay down a "just the
facts"
> baseline that lets you get in and out fast.
>
> Anyway, we hope you find it useful. Thanks for using Puppet.
>
> --
> You received this message because you are subscribed to the Google Groups
> "Puppet Users" group.
> To view this discussion on the web visit
> https://groups.google.com/d/msg/puppet-users/-/bDBvT082CjQJ.
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-- 
Erik Dalén

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On Thursday, August 23, 2012 1:55:15 AM UTC-7, Erik Dalén wrote:
> But I''m wondering about the section on "Reserved Variable
Names" that
> says that reusing fact names as variables in a local scope may cause 
> malfunctions. This is something I''ve done quite a lot without any 
> problem, is it considered unsupported and might break in future 
> versions? 
>
No no -- it''s just that if you''re declaring a class from
someone else''s
module and they didn''t use the $::fact idiom, overriding a fact might 
change the class''s environment enough to break it. If you know
what''s going
on in your classes you''re fine, and if you''re overriding a
fact in a scope
that doesn''t beget any other scopes you''re fine. I should
rewrite that to
be more clear!

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Hi Nick, I have a suggestion.  In
http://docs.puppetlabs.com/puppet/2.7/reference/lang_datatypes.html#hashes
it would be helpful to have a hash example that contains multiple keys
each with multiple subkeys.  The way the commas are distributed in
that scenario is different from how commas are handled in resources
and properties  which can be confusing.  After reading the hash
section I ended up having to google for a more complete example and
I''m sure I''m not the only one.

Thanks again for your work, I really like the new layout.

-Aaron

On Tue, Aug 21, 2012 at 1:40 PM, Nick Fagerlund
<nick.fagerlund@puppetlabs.com> wrote:
> Hi all,
>
> I''ve finished the all new Puppet 2.7 language reference. EXCITING!
Well,
> exciting to me, at least. Table of contents:
>
> http://docs.puppetlabs.com/puppet/2.7/reference/
>
> Visual index (for when you know what you''re looking for but you
don''t know
> what it''s called):
>
> http://docs.puppetlabs.com/puppet/2.7/reference/lang_visual_index.html
>
> And of course, use the navigation in the left sidebar to jump between
pages.
>
> Our goal here is to nail down every detail of how the Puppet language
works,
> then cut new versions along with major Puppet releases. We''ll
eventually be
> expanding this versioned document with non-language details --
we''ve been
> referring to this plan as the "Puppet reference manual." Its
purpose isn''t
> to replace any of the guides or how-tos, but to lay down a "just the
facts"
> baseline that lets you get in and out fast.
>
> Anyway, we hope you find it useful. Thanks for using Puppet.
>
> --
> You received this message because you are subscribed to the Google Groups
> "Puppet Users" group.
> To view this discussion on the web visit
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On Thursday, August 23, 2012 12:47:16 PM UTC-7, Aaron Grewell
wrote:
>
> In 
> http://docs.puppetlabs.com/puppet/2.7/reference/lang_datatypes.html#hashes 
> it would be helpful to have a hash example that contains multiple keys 
> each with multiple subkeys. 
>
You''re right, I''ll put one in. (Although since sometime before
2.7, you can
actually use trailing commas in hashes the same way you do in resource 
declarations. I''ll add that to the docs too!)

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EXCELLENT GUIDE !!!
I which that had been available when I started on Geppetto :)

Here are some things that I would like the documentation to clarify:

- How do I create strings that span multiple lines? (Since there is no
string concatenation operator ''x'' + ''y'' does
not work). Can I write a
string that continues on the next line? If so, is the newline included 
or not? Can I tell it to not include the newline? How is the line-break 
encoded - if it is CR-LF in the pp-file, does the string contain that at 
runtime?

- Can I write more complex expressions in an interpolation? Can I do 
something like "The sum is ${$a + $b}", and if that is the case, is it
possible to have any expression interpolated (including nested strings 
with interpolation)?

- The compiler allows ${a} without double quotes - which is a string 
interpolation of $a. Which IIRC is slightly different than using $a 
directly (getting an empty string if $a is undefined). I don''t recall 
seeing that in the documentation on the first read through.

- IIRC, Use of numerical variables $0 - $9 as a result of regular 
expression matching was not mentioned. When talking about variables I 
think it is worth noting that you should not use $0 - $9 for anything 
else (or you may be surprised as the regexp match creates an inner scope 
where these variables refer to match results). (IMO use of $0-$9 should 
be reserved for that purpose and they should not be assignable).

- Arrays and Hashes are mutable; which is either an bug or a language 
feature. While it is not allowed to directly change a variable, it can 
be indirectly modified if it refers to an array or hash. Great if the 
documentation can clarify if this is a supported feature or should be 
avoided. i.e. $a = [1,2,3] $a[0] = 10. (IMO, this is problematic as any 
logic can refer to the variable and assign to an entry - at least last I 
tried).


Again, an excellent language reference!
Regards
- henrik


On 2012-21-08 22:40, Nick Fagerlund wrote:
> Hi all,
>
> I''ve finished the all new Puppet 2.7 language reference. EXCITING!
Well,
> exciting to me, at least. Table of contents:
>
> http://docs.puppetlabs.com/puppet/2.7/reference/
>
> Visual index (for when you know what you''re looking for but you
don''t
> know what it''s called):
>
> http://docs.puppetlabs.com/puppet/2.7/reference/lang_visual_index.html
>
> And of course, use the navigation in the left sidebar to jump between
> pages.
>
> Our goal here is to nail down every detail of how the Puppet language
> works, then cut new versions along with major Puppet releases.
We''ll
> eventually be expanding this versioned document with non-language
> details -- we''ve been referring to this plan as the "Puppet
reference
> manual." Its purpose isn''t to replace any of the guides or
how-tos, but
> to lay down a "just the facts" baseline that lets you get in and
out fast.
>
> Anyway, we hope you find it useful. Thanks for using Puppet.
>
> --
> You received this message because you are subscribed to the Google
> Groups "Puppet Users" group.
> To view this discussion on the web visit
> https://groups.google.com/d/msg/puppet-users/-/bDBvT082CjQJ.
> 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.
> For more options, visit this group at
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On Thu, Aug 23, 2012 at 4:32 PM, Nick Fagerlund
<nick.fagerlund@puppetlabs.com> wrote:
>
>
> On Thursday, August 23, 2012 12:47:16 PM UTC-7, Aaron Grewell wrote:
>>
>> In
>>
http://docs.puppetlabs.com/puppet/2.7/reference/lang_datatypes.html#hashes
>> it would be helpful to have a hash example that contains multiple keys
>> each with multiple subkeys.
>
>
> You''re right, I''ll put one in. (Although since sometime
before 2.7, you can
> actually use trailing commas in hashes the same way you do in resource
> declarations. I''ll add that to the docs too!)
>
That looks really good.  After reviewing my code, I suspect that my
issue was not that Puppet''s approach was inconsistent but rather that
I never use this kind of nesting in my resource declarations.  It''s
common for hashes though, so the new examples are a definite plus.

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Err, I think google groups may have eaten my response. But THANK YOU, and 
I''m adjusting the guide to patch all these holes as we speak. 

On Friday, August 24, 2012 6:33:01 AM UTC-7, Henrik Lindberg
wrote:
>
> EXCELLENT GUIDE !!! 
> I which that had been available when I started on Geppetto :) 
>
> Here are some things that I would like the documentation to clarify: 
>
> - How do I create strings that span multiple lines? (Since there is no 
> string concatenation operator ''x'' + ''y''
does not work). Can I write a
> string that continues on the next line? If so, is the newline included 
> or not? Can I tell it to not include the newline? How is the line-break 
> encoded - if it is CR-LF in the pp-file, does the string contain that at 
> runtime? 
>
> - Can I write more complex expressions in an interpolation? Can I do 
> something like "The sum is ${$a + $b}", and if that is the case,
is it
> possible to have any expression interpolated (including nested strings 
> with interpolation)? 
>
> - The compiler allows ${a} without double quotes - which is a string 
> interpolation of $a. Which IIRC is slightly different than using $a 
> directly (getting an empty string if $a is undefined). I don''t
recall
> seeing that in the documentation on the first read through. 
>
> - IIRC, Use of numerical variables $0 - $9 as a result of regular 
> expression matching was not mentioned. When talking about variables I 
> think it is worth noting that you should not use $0 - $9 for anything 
> else (or you may be surprised as the regexp match creates an inner scope 
> where these variables refer to match results). (IMO use of $0-$9 should 
> be reserved for that purpose and they should not be assignable). 
>
> - Arrays and Hashes are mutable; which is either an bug or a language 
> feature. While it is not allowed to directly change a variable, it can 
> be indirectly modified if it refers to an array or hash. Great if the 
> documentation can clarify if this is a supported feature or should be 
> avoided. i.e. $a = [1,2,3] $a[0] = 10. (IMO, this is problematic as any 
> logic can refer to the variable and assign to an entry - at least last I 
> tried). 
>
>
> Again, an excellent language reference! 
> Regards 
> - henrik 
>
>
> On 2012-21-08 22:40, Nick Fagerlund wrote: 
> > Hi all, 
> > 
> > I''ve finished the all new Puppet 2.7 language reference.
EXCITING! Well,
> > exciting to me, at least. Table of contents: 
> > 
> > http://docs.puppetlabs.com/puppet/2.7/reference/ 
> > 
> > Visual index (for when you know what you''re looking for but
you don''t
> > know what it''s called): 
> > 
> > http://docs.puppetlabs.com/puppet/2.7/reference/lang_visual_index.html
> > 
> > And of course, use the navigation in the left sidebar to jump between 
> > pages. 
> > 
> > Our goal here is to nail down every detail of how the Puppet language 
> > works, then cut new versions along with major Puppet releases.
We''ll
> > eventually be expanding this versioned document with non-language 
> > details -- we''ve been referring to this plan as the
"Puppet reference
> > manual." Its purpose isn''t to replace any of the guides
or how-tos, but
> > to lay down a "just the facts" baseline that lets you get in
and out
> fast. 
> > 
> > Anyway, we hope you find it useful. Thanks for using Puppet. 
> > 
> > -- 
> > You received this message because you are subscribed to the Google 
> > Groups "Puppet Users" group. 
> > To view this discussion on the web visit 
> > https://groups.google.com/d/msg/puppet-users/-/bDBvT082CjQJ. 
> > To post to this group, send email to
puppet...@googlegroups.com<javascript:>.
>
> > To unsubscribe from this group, send email to 
> > puppet-users...@googlegroups.com <javascript:>. 
> > For more options, visit this group at 
> > http://groups.google.com/group/puppet-users?hl=en. 
>
>
>
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Yeah that reply isn''t coming back. Anyway, I was totally hoping
you''d chime
in with some holes you found. :)

On Friday, August 24, 2012 6:33:01 AM UTC-7, Henrik Lindberg wrote:
>
> - How do I create strings that span multiple lines? (Since there is no 
> string concatenation operator ''x'' + ''y''
does not work). Can I write a
> string that continues on the next line? If so, is the newline included 
> or not? Can I tell it to not include the newline? How is the line-break 
> encoded - if it is CR-LF in the pp-file, does the string contain that at 
> runtime? 
>
Added this! Line breaks are preserved, line break format is preserved (so 
whatever you used in the file, that''s what you get in your strings, I
don''t
like it either), you can use \n to get literal Unix line breaks, but you 
can''t use \r\n to get Windows ones because \r doesn''t exist.
There isn''t an
ignore-whitespace option for strings. 

> - Can I write more complex expressions in an interpolation? Can I do 
> something like "The sum is ${$a + $b}", and if that is the case,
is it
> possible to have any expression interpolated (including nested strings 
> with interpolation)? 
>
Nope! Thanks for reminding me about this, I remember trying to make Puppet 
do this and being disappointed. 
 
>
> - The compiler allows ${a} without double quotes - which is a string 
> interpolation of $a. Which IIRC is slightly different than using $a 
> directly (getting an empty string if $a is undefined). I don''t
recall
> seeing that in the documentation on the first read through. 
>
If the parser allows this, it''s getting blocked elsewhere in the
system,
because Puppet definitely fails compilation hard if you try to use ${var} 
outside a double-quoted string. 
  
> - IIRC, Use of numerical variables $0 - $9 as a result of regular 
> expression matching was not mentioned. When talking about variables I 
> think it is worth noting that you should not use $0 - $9 for anything 
> else (or you may be surprised as the regexp match creates an inner scope 
> where these variables refer to match results). (IMO use of $0-$9 should 
> be reserved for that purpose and they should not be assignable). 
>
Ahhh good call. Actually, I just tested and it looks like assigning 
directly to $\d is a no-op??? That''s pretty wild. Anyway, putting them
in
as reserved variable names.  

> - Arrays and Hashes are mutable; which is either an bug or a language 
> feature. While it is not allowed to directly change a variable, it can 
> be indirectly modified if it refers to an array or hash. Great if the 
> documentation can clarify if this is a supported feature or should be 
> avoided. i.e. $a = [1,2,3] $a[0] = 10. (IMO, this is problematic as any 
> logic can refer to the variable and assign to an entry - at least last I 
> tried). 
>
D:< EWW. "Problematic" is putting it mildly, especially since
behavior is
inconsistent between arrays and hashes. (Both can add, only arrays can 
reassign to existing indexes.) But I''d better document it anyhow. 

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Hi,

On 2012-25-08 1:02, Nick Fagerlund wrote:
> Yeah that reply isn''t coming back. Anyway, I was totally hoping
you''d
> chime in with some holes you found. :)
>
Comments below...
> On Friday, August 24, 2012 6:33:01 AM UTC-7, Henrik Lindberg wrote:
>
>     - How do I create strings that span multiple lines? (Since there is no
>     string concatenation operator ''x'' +
''y'' does not work). Can I write a
>     string that continues on the next line? If so, is the newline included
>     or not? Can I tell it to not include the newline? How is the line-break
>     encoded - if it is CR-LF in the pp-file, does the string contain
>     that at
>     runtime?
 >
> Added this! Line breaks are preserved, line break format is preserved
> (so whatever you used in the file, that''s what you get in your
strings,
> I don''t like it either), you can use \n to get literal Unix line
breaks,
> but you can''t use \r\n to get Windows ones because \r
doesn''t exist.
> There isn''t an ignore-whitespace option for strings.>
>
So, I guess you really have to use a template file instead if you want 
something long and/or need more control over whitepsace.
>     - Can I write more complex expressions in an interpolation? Can I do
>     something like "The sum is ${$a + $b}", and if that is the
case, is it
>     possible to have any expression interpolated (including nested strings
>     with interpolation)?
>
>
> Nope! Thanks for reminding me about this, I remember trying to make
> Puppet do this and being disappointed.
>
The thing is that it is supported in the parser (at least IIRC, but I 
have not checked the last couple of months if anything changed). So the 
question is if it is supposed to be in the language or not even if not 
implemented correctly (i.e. language bug, or runtime bug?).
>
>     - The compiler allows ${a} without double quotes - which is a string
>     interpolation of $a. Which IIRC is slightly different than using $a
>     directly (getting an empty string if $a is undefined). I don''t
recall
>     seeing that in the documentation on the first read through.
>
>
> If the parser allows this, it''s getting blocked elsewhere in the
system,
> because Puppet definitely fails compilation hard if you try to use
> ${var} outside a double-quoted string.
>
Makes sense, and I should adjust Geppetto validation. It now accepts 
${var} to have the same meaning as "${var}". One wonders why it is in 
the grammar in the first place - maybe just a bug, or to give an 
opportunity to say "${var} must be placed in a double quoted string?
>     - IIRC, Use of numerical variables $0 - $9 as a result of regular
>     expression matching was not mentioned. When talking about variables I
>     think it is worth noting that you should not use $0 - $9 for anything
>     else (or you may be surprised as the regexp match creates an inner
>     scope
>     where these variables refer to match results). (IMO use of $0-$9 should
>     be reserved for that purpose and they should not be assignable).
>
>
> Ahhh good call. Actually, I just tested and it looks like assigning
> directly to $\d is a no-op??? That''s pretty wild. Anyway, putting
them
> in as reserved variable names.
>
>
>     - Arrays and Hashes are mutable; which is either an bug or a language
>     feature. While it is not allowed to directly change a variable, it can
>     be indirectly modified if it refers to an array or hash. Great if the
>     documentation can clarify if this is a supported feature or should be
>     avoided. i.e. $a = [1,2,3] $a[0] = 10. (IMO, this is problematic as any
>     logic can refer to the variable and assign to an entry - at least
>     last I
>     tried).
>
>
> D:< EWW. "Problematic" is putting it mildly, especially since
behavior
> is inconsistent between arrays and hashes. (Both can add, only arrays
> can reassign to existing indexes.) But I''d better document it
anyhow.
>
The thing is, if arrays and hashes are immutable (as they should be), 
there is no meaning to have [] operator produce a Lvalue at all - i.e. 
can''t assign something to the result. The only possible interpretation 
of say $a[3]= 10 when they are immutable is to create a new variable $a 
with an array assigned where 0-2 are undefined and 3 is assigned to 10. 
Seems like a completely useless construct.

Passing arrays and hashes to functions is naturally a potential danger.

- henrik

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On 2012-25-08 1:02, Nick Fagerlund wrote:
>     - Can I write more complex expressions in an interpolation? Can I do
>     something like "The sum is ${$a + $b}", and if that is the
case, is it
>     possible to have any expression interpolated (including nested strings
>     with interpolation)?
>
>
> Nope! Thanks for reminding me about this, I remember trying to make
> Puppet do this and being disappointed.
I just tested on puppet 2.7.14...

puppet apply -e ''$x = 1 $y =2 $b="x${$x+$y}x"
notice($b)''
notice: Scope(Class[main]): x3x
notice: Finished catalog run in 0.01 seconds

And

puppet apply -e ''$x = 1 $y =2
$b="x${"abc${$x+$y}abc"}x" notice($b)''
notice: Scope(Class[main]): xabc3abcx
notice: Finished catalog run in 0.01 seconds

So - seems to work just fine - at least simple, complex things :)

- henrik

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Just to make this extra fun....

You CAN change variables after they''ve been assigned.

If you assign a new value to the variable in a template, it will pick
up the new value.

Note that this should NOT be used as a feature but I''m sure
it''ll bite
someone like it did me at some point since it lovely and random but,
once set, is set for that variable as long as it''s memory resident.

Note: I haven''t checked that this still happens in a while but I would
bet that it does.

Trevor

On Fri, Aug 24, 2012 at 7:02 PM, Nick Fagerlund
<nick.fagerlund@puppetlabs.com> wrote:
>> - Arrays and Hashes are mutable; which is either an bug or a language
>> feature. While it is not allowed to directly change a variable, it can
>> be indirectly modified if it refers to an array or hash. Great if the
>> documentation can clarify if this is a supported feature or should be
>> avoided. i.e. $a = [1,2,3] $a[0] = 10. (IMO, this is problematic as any
>> logic can refer to the variable and assign to an entry - at least last
I
>> tried).
>
>
> D:< EWW. "Problematic" is putting it mildly, especially since
behavior is
> inconsistent between arrays and hashes. (Both can add, only arrays can
> reassign to existing indexes.) But I''d better document it anyhow.
>

-- 
Trevor Vaughan
Vice President, Onyx Point, Inc
(410) 541-6699
tvaughan@onyxpoint.com

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On Sunday, August 26, 2012 6:44:25 PM UTC-7, Henrik Lindberg wrote:
>
> I just tested on puppet 2.7.14... 
>
> puppet apply -e ''$x = 1 $y =2 $b="x${$x+$y}x"
notice($b)''
> notice: Scope(Class[main]): x3x 
> notice: Finished catalog run in 0.01 seconds 
>
> And 
>
> puppet apply -e ''$x = 1 $y =2
$b="x${"abc${$x+$y}abc"}x" notice($b)''
> notice: Scope(Class[main]): xabc3abcx 
> notice: Finished catalog run in 0.01 seconds 
>
> So - seems to work just fine - at least simple, complex things :) 
>
> - henrik 
>
 

WAT.

Oh wow, this gets kind of weird. 
https://gist.github.com/f870b2c33ffa466c8f18 

I could have sworn that didn''t used to work, but I just tested it back
to
2.6.3, and it''s solid. Weird. 

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On Monday, August 27, 2012 7:09:39 AM UTC-7, Trevor Vaughan
wrote:
>
> Just to make this extra fun.... 
>
> You CAN change variables after they''ve been assigned. 
>
> If you assign a new value to the variable in a template, it will pick 
> up the new value. 
>
>
Ah ha, but templates are not part of the puppet language''s grammar. :) 

(In seriousness, I think we consider that a bug.)

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I get it, but it would be nice to explicitly tell people to be careful
about this when talking about variables and pitfalls.

Trevor

On Mon, Aug 27, 2012 at 2:43 PM, Nick Fagerlund
<nick.fagerlund@puppetlabs.com> wrote:
>
>
> On Monday, August 27, 2012 7:09:39 AM UTC-7, Trevor Vaughan wrote:
>>
>> Just to make this extra fun....
>>
>> You CAN change variables after they''ve been assigned.
>>
>> If you assign a new value to the variable in a template, it will pick
>> up the new value.
>>
>
> Ah ha, but templates are not part of the puppet language''s
grammar. :)
>
> (In seriousness, I think we consider that a bug.)
>
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(410) 541-6699
tvaughan@onyxpoint.com

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On Monday, August 27, 2012 11:55:23 AM UTC-7, Trevor Vaughan
wrote:
>
> I get it, but it would be nice to explicitly tell people to be careful 
> about this when talking about variables and pitfalls. 
>
Okay, fair point. I''ll put a note. 

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On Friday, August 24, 2012 6:02:54 PM UTC-5, Nick Fagerlund
wrote:
>
> Yeah that reply isn''t coming back. Anyway, I was totally hoping
you''d
> chime in with some holes you found. :)
>
> On Friday, August 24, 2012 6:33:01 AM UTC-7, Henrik Lindberg wrote:
>
>> - Arrays and Hashes are mutable; which is either an bug or a language 
>> feature. While it is not allowed to directly change a variable, it can 
>> be indirectly modified if it refers to an array or hash. Great if the 
>> documentation can clarify if this is a supported feature or should be 
>> avoided. i.e. $a = [1,2,3] $a[0] = 10. (IMO, this is problematic as any
>> logic can refer to the variable and assign to an entry - at least last
I
>> tried). 
>>
>
> D:< EWW. "Problematic" is putting it mildly, especially since
behavior is
> inconsistent between arrays and hashes. (Both can add, only arrays can 
> reassign to existing indexes.) But I''d better document it anyhow. 
>

Good grief, don''t do that!  If it actually gets published in an
official PL
document then it may be Puppet 4 before it can be removed!


John

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On Monday, August 27, 2012 1:20:53 PM UTC-7, jcbollinger
wrote:
>
>
> D:< EWW. "Problematic" is putting it mildly, especially since
behavior is
>> inconsistent between arrays and hashes. (Both can add, only arrays can 
>> reassign to existing indexes.) But I''d better document it
anyhow.
>>
>
>
> Good grief, don''t do that!  If it actually gets published in an
official
> PL document then it may be Puppet 4 before it can be removed!
>
>
Well, this runs up against the blurry boundary between the docs and the 
ticket tracker. Obviously I''m not writing every outstanding bug into
the
language reference, but it IS meant to be a record of everything we know 
about the Puppet language as she is actually played, so there are a few 
bugs like this that deserve a mention in it (along with a big fat DON''T
DO
THIS sign). 

For the time being, I''m putting notes by a few things saying that
they''re
considered bugs and may be removed without a deprecation period. My 
approach may change a bit over time?

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On 2012-28-08 24:34, Nick Fagerlund wrote:
> ...blurry...
> ...ticket tracker ... outstanding bug
>...DON''T DO THIS...
Ah,
which reminded me about the fun and games that can be played with node 
inheritance and regular expressions. There is a bug logged for that.

Problem being that a node can inherit from another by referencing it via 
its "name". The "name" can be a regular expression (which is
reasonable
to match against hostnames). What is not reasonable is to have complex 
RHS expression that inherits based on a regexp.

A regexp may also match the special "default" node as well - see:

http://projects.puppetlabs.com/issues/7433
http://projects.puppetlabs.com/issues/7423

What - that issue (7423) was closed because 2.6 version was deleted? The 
problem still exists because nodeparent uses rule hostname
https://github.com/puppetlabs/puppet/blob/3.x/lib/puppet/parser/grammar.ra#L708

and hostname allows regexp

https://github.com/puppetlabs/puppet/blob/3.x/lib/puppet/parser/grammar.ra#L677

I re-opened the issue 7423.

Anyway, I agree with the approach to document how it *should be*, and 
when the reality happens to allow something completely different it 
should be noted.

Language design and implementation is tricky -
https://www.destroyallsoftware.com/talks/wat
NaNaNaNa - Batman ! (around 3:50 in if you are impatient).


Regards
- henrik


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https://github.com/puppetlabs/puppet/commit/193e19eb14ff640a68f2a21fd525ef6c8825dbf2

Don''t think that was in the language guide.

And the new ''unless'' statement in 3.0.

- henrik

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> And of course, use the navigation in the left sidebar to jump between
pages.
Next/Back links at the top, and bottom of each page would be nice for
reading through the whole manual. Would save a little bit of effort
over scrolling back up to the contents after finishing reading a page.

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