The document summarizes new features and changes coming in Puppet 4.0, including language cleanup for consistency and reducing surprises, new features like iteration functions and resource expressions, an optional type system, embedded Puppet templates, and heredocs for multiline strings. It provides examples of the new features and discusses transitioning to Puppet 4.0.

2. Yamata
no
Orochi

6. Puppet
Language
4.0
henrik.lindberg@puppetlabs.com

11. notice 1 => 1
notice 1 + 2 => syntax error
notice(1 + 2) => 3
notice 1,2,3 => 1 2 3
notice [1,2,3] => 1 2 3
notice [1,2],3 => 1 2 3
notice 5 in [5] => true
notice (4+1) in [5] => error, not a string
notice 5 in [4+1] => false
notice 5.0 in [5] => false
notice(0xff =~ /5/) => false
notice((0xfe+1) =~/5/) => true
notice { a=>10 } => error, no title

13. Puppet
4.0
• Language
Cleanup
– Sanity,
Principle
of
Least
Surprise
– Expressions,
Expressions,
Expressions
• Features
– Misc
enhancements
– Resource
Expression
Features
– IteraGon
– Type
System
/
OpGonal
Typing
– Embedded
Puppet
Templates
(EPP)
– Heredoc

14. Cleanup
• Language
SpecificaGon
–
yes
we
have
one
– hQps://github.com/puppetlabs/puppet-­‐specificaGons
• Numbers
are
Numbers
• No
magic
to-­‐string
for
=~ !~ in
• Upper
case
bare
words
are
Type
References
• Empty
string
is
not
undef
(and
thus
"thruty")
• InterpolaGon
follows
specified
rules
• +=,
[]=
removed,
no
more
mutaGon

16. Misc
new
features
1(7)
• Concatenate
Arrays
with
+
[1,2,3] + [4,5,6] => [1,2,3,4,5,6]
• Merge
Hashes
with
+
{a=>1} + {b=>2} => {a=>1, b=>2}
• Delete
with
-­‐
[1,2,3] – [2, 3] => [1]
{a=>1, b=>2, c=>3} – [a,c] => {b=>2}

17. Misc
new
features
2(7)
• Append
to
Array
with
<<
[1,2,3] << 4 => [1,2,3,4]
[1,2,3] << [4,5,6] => [1,2,3,[4,5,6]]

18. Misc
new
features
3(7)
• Unfold
with
unary
*
$a = [2,3]
$b = [1, *$a, 4] => [1,2,3,4]
• Unfold
in
case
opGon,
selector
and
call
$a = [1,2,3]
case 1 {
*$a : { # 1 or 2 or 3
}
}
notice *$a => 1,2,3
notice $a => [1,2,3]

19. Misc
new
features
4(7)
• Substring
in
string
'cd' in "abcde" => true
• Substring
with
[]
"xyzabcdef"[3,3] => "abc"
"xyzabcdef"[3] => "a"
"xyzabcdef"[3,-2] => "abcde"

20. Misc
new
features
5(7)
• Matches
with
Regexp
in
String
form
$a = "example.com"
$url =~ "http://$a.*"

21. Misc
new
features
6(7)
• Detailed
Error
Messages
– SemanGc
validaGon
unless
lex
or
syntax
errors
– Outputs
posiGon
on
line
– Can
report
more
than
one
error

22. Expression
Based
Grammar
6(7)
• if,
unless,
case
are
expressions
notice if 1 > 2 { true } else { false }
# => false
$a =
case 2 {
1, 2, 3: { yes }
default: { no }
}
# => $a == yes

23. Resource
Expression

24. Local
Defaults
file {
default:
mode => '444',
owner => 'admin';
title:
. . . ;
}

25. Unfold
Hash
file {
default:
* => $defaults_hash;
'tmp/foo':
mode => '666',
* => $params_hash;
}

26. Create
Resources
Equiv.
in
Puppet
Resource[$type] {
default:
* => $defaults_hash;
$titles:
* => $params_hash;
}

28. LOOOOOOOPS
• Iterate
over:
– Arrays
– Hashes
– Strings
– Integer
ranges
• Implemented
as
funcGons
taking
callable
code
blocks
(lambdas)
=
open
design
• Calls
can
now
be
expressed
from
leh
to
right
using
'.'
notaGon

29. each
• Do
something
with
each
element
• Returns
LHS
[1,2,3].each |$x| { notice $x }
each([1,2,3]) |$x| { notice $x }

30. map
• Transform
each
element
• Returns
transformed
result
[1,2,3].map |$x| { $x*10 }
=> [10,20,30]

31. filter
• Produces
elements
that
match
• Returns
filtered
result
[1,2,3].filter|$x| { $x >= 2 }
=> [2,3]

32. reduce
• Transforms
/
reduces
many
to
one
• Feeds
seed/previous
result
into
next
iteraGon
• Returns
transformed
result
[1,2,3].reduce |$result, $x| {
$result + $x
}
=> 6

33. And
more

37. E-­‐I-­‐E-­‐I-­‐O

39. E-­‐I-­‐E-­‐I-­‐O

41. E-­‐I-­‐E-­‐I-­‐O

44. E-­‐I-­‐E-­‐I-­‐O

46. The
Puppet
Type
System
Cow
Integer

47. Puppet
Types
• Puppet
Types
are
first
order
objects
(they
can
be
assigned
and
passed
around
in
variables)
• Uses
syntax
familiar
from
Resource
–
i.e.
Class,
File,
User,
where
[
]
applied
to
the
type
makes
it
more
specific
–
e.g.
File['foo']

48. Example
Integer
# All integers
Integer
# All integers >=42
Integer[42]
# All integers >=42 and <=142
Integer[42,142]

49. AutomaGc
type
checking!
define mytype(Integer[80,443] $port){
# port guaranteed to be integer
# and between 80 and 443
# otherwise an error
}

50. More
advanced
type
checking!
define mytype($port) {
assert_type(Integer[80,443], $port) |$expected, $got| {
warn("Bad port $got, expected $expected. Using port 80.")
80
}
}
•
Code
block
called
if
given
does
not
match
•
…do
what
you
want,
fail,
warn,
return
default

51. OperaGons
on
Type
• Since
a
Type
is
a
kind
of
PaQern…
– Match
with
=~
and
!~
– Match
in
case
expression
• Since
Types
are
defined
in
a
hierarchy:
– Compare
types
with
<,
<=,
>,
>=
# is $x an integer ?
$x =~ Integer
# is $t more specific than Integer
$t = Integer[80, 144]
$t < Integer

52. Type
Hierarchy
Any
|- Scalar
| |- Numeric
| | |- Integer[from, to]
| | |- Float[from, to]
| |
| |- String[from, to]
| | |- Enum[*strings]
| | |- Pattern[*patterns]
| |
| |- Boolean
| |- Regexp[pattern_string]

53. Type
Hierarchy
Any
|- Collection
| |- Array[T]
| | |- Tuple[T*, from, to]
| |
| |- Hash[K, V]
| | |- Struct[{ key => T, ...}]
|
|- Variant[T*]
|- Optional[T]
|
|- Undef
|- Default
|
|- Type[T]

54. Type
Hierarchy
Any
|- CatalogEntry
| |- Resource[type_name, title]
| |- Class[class_name]
|
|- Undef
|- Data
| |- Scalar
| |- Array[Data]
| |- Hash[Scalar, Data]
| |- Undef

55. EPP

56. EPP
–
Templates
in
Puppet
• Same
template
markup
as
ERB
– Logic
is
Puppet
instead
of
Ruby
AND
• Can
be
parameterized
!
• Use
funcGons
epp(template)
inline_epp(string)
• instead
of
template()
inline_template()

57. Example
EPP
$x = 'human'
inline_epp('This is not the <%= $x %> you are looking
for.')
# => 'This is not the human you are looking for.'
$x = 'human'
inline_epp('This is not the <%= $x %> you are looking
for.', { 'x' => 'droid'})
# => 'This is not the droid you are looking for.'
<%- |$x = 'human'| -%>
This is not the <%= $x %> you are looking for.

58. Heredoc

59. Puppet
Heredoc
• For
more
detailed
control
over
a
block
of
text
• No,
or
selected
set
of
escapes
• InterpolaGon
or
no
interpolaGon
• Can
be
syntax
checked
by
parser
(JSon
in
core,
can
add
plugin
language
support)
• Control
over
leh
margin

60. Heredoc
-­‐
Syntax
ENDS-­‐HERE
anything
not
in
<text>
"ENDS-­‐HERE"
with
interpola:on
:json
syntax
check
result
/tsrn$L
turns
on
escape
/
turns
on
all
@( ["]<endtag>["] [:<syntax>] [/<escapes>] )
<text>
[|][-] <endtag>
|
set
le=
margin
-­‐
trim
trailing
t
tab
s
space
r
return
n
new-­‐line
$
$
L
<end
of
line>

61. Puppet
Heredoc
Example
#.........1.........2.........3.........4.........5....
$a = @(END)
This is indented 2 spaces in the source, but produces
a result flush left with the initial 'T'
This line is thus indented 2 spaces.
| END
#.........1.........2.........3.........4.........5....
foo(@(FIRST), @(SECOND))
This is the text for the first heredoc
FIRST
This is the text for the second
SECOND

62. Ruby
API

63. Ruby
API
• 4x
FuncGon
API
– type
checked
– dispatch
to
impl
based
on
given
types
– more
powerful
– safer
• Binder
– composable
type
safe
injecGon
– for
plugins
and
data
(e.g.
syntax
checkers)

64. Summary
• Language
Cleanup
• More
strict
• New
Features
• BeQer
Error
Messages
• IteraGon
• Type
System
• Puppet
Templates
–
EPP
• Heredoc

65. In
pracGce
• Run
now
with
–parser
future
• Fix
deprecaGons
and
issues
• Make
backwards
compaGble
changes
and
conGnue
in
producGon
on
3x
• Test
carefully
and
conGnue
running
on
what
will
be
Puppet
4.0
• 4.0
expected
release
before
end
of
the
year

67. Links
• github/puppetlabs/puppet-­‐specificaGons
• hQp://puppet-­‐on-­‐the-­‐edge.blogspot.com/
• TwiQer
@hel
• IRC
helindbe