From 823a352f0f47d4481844bb6b6a6c00224ed556b8 Mon Sep 17 00:00:00 2001
From: Dmitry Ilyin <dilyin@mirantis.com>
Date: Tue, 1 Sep 2015 21:39:16 +0300
Subject: Add a new function "try_get_value"
* Extracts a value from a deeply-nested data structure
* Returns default if a value could not be extracted
---
lib/puppet/parser/functions/try_get_value.rb | 77 ++++++++++++++++++++++++++++
1 file changed, 77 insertions(+)
create mode 100644 lib/puppet/parser/functions/try_get_value.rb
(limited to 'lib/puppet/parser/functions')
diff --git a/lib/puppet/parser/functions/try_get_value.rb b/lib/puppet/parser/functions/try_get_value.rb
new file mode 100644
index 0000000..0c19fd9
--- /dev/null
+++ b/lib/puppet/parser/functions/try_get_value.rb
@@ -0,0 +1,77 @@
+module Puppet::Parser::Functions
+ newfunction(
+ :try_get_value,
+ :type => :rvalue,
+ :arity => -2,
+ :doc => <<-eos
+Looks up into a complex structure of arrays and hashes and returns a value
+or the default value if nothing was found.
+
+Key can contain slashes to describe path components. The function will go down
+the structure and try to extract the required value.
+
+$data = {
+ 'a' => {
+ 'b' => [
+ 'b1',
+ 'b2',
+ 'b3',
+ ]
+ }
+}
+
+$value = try_get_value($data, 'a/b/2', 'not_found', '/')
+=> $value = 'b3'
+
+a -> first hash key
+b -> second hash key
+2 -> array index starting with 0
+
+not_found -> (optional) will be returned if there is no value or the path did not match. Defaults to nil.
+/ -> (optional) path delimiter. Defaults to '/'.
+
+In addition to the required "key" argument, "try_get_value" accepts default
+argument. It will be returned if no value was found or a path component is
+missing. And the fourth argument can set a variable path separator.
+ eos
+ ) do |args|
+ path_lookup = lambda do |data, path, default|
+ debug "Try_get_value: #{path.inspect} from: #{data.inspect}"
+ if data.nil?
+ debug "Try_get_value: no data, return default: #{default.inspect}"
+ break default
+ end
+ unless path.is_a? Array
+ debug "Try_get_value: wrong path, return default: #{default.inspect}"
+ break default
+ end
+ unless path.any?
+ debug "Try_get_value: value found, return data: #{data.inspect}"
+ break data
+ end
+ unless data.is_a? Hash or data.is_a? Array
+ debug "Try_get_value: incorrect data, return default: #{default.inspect}"
+ break default
+ end
+
+ key = path.shift
+ if data.is_a? Array
+ begin
+ key = Integer key
+ rescue ArgumentError
+ debug "Try_get_value: non-numeric path for an array, return default: #{default.inspect}"
+ break default
+ end
+ end
+ path_lookup.call data[key], path, default
+ end
+
+ data = args[0]
+ path = args[1] || ''
+ default = args[2]
+ separator = args[3] || '/'
+
+ path = path.split separator
+ path_lookup.call data, path, default
+ end
+end
--
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