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Dmitry Ilyin
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Add a new function "getpath"
* Extracts a value from a deeply-nested data structure * Returns default if a value could not be extracted
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‎README.markdown

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@@ -301,6 +301,40 @@ For example, the following returns 'param_value':
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*Type*: rvalue.
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#### `getpath`
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*Type*: rvalue.
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Looks up into a complex structure of arrays and hashes and returns a value
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or the default value if nothing was found.
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Key can contain slashes to describe path components. The function will go down
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the structure and try to extract the required value.
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$data = {
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'a' => {
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'b' => [
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'b1',
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'b2',
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'b3',
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]
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}
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}
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$value = get_path($data, 'a/b/2', 'not_found', '/')
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=> $value = 'b3'
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a -> first hash key
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b -> second hash key
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2 -> array index starting with 0
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not_found -> (optional) will be returned if there is no value or the path did not match. Defaults to nil.
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/ -> (optional) path delimiter. Defaults to '/'.
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In addition to the required "key" argument, "getpath" accepts default
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argument. It will be returned if no value was found or a path component is
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missing. And the fourth argument can set a variable path separator.
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#### `getvar`
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Looks up a variable in a remote namespace.

‎lib/puppet/parser/functions/getpath.rb

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module Puppet::Parser::Functions
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newfunction(
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:getpath,
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:type => :rvalue,
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:arity => -2,
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:doc => <<-eos
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Looks up into a complex structure of arrays and hashes and returns a value
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or the default value if nothing was found.
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Key can contain slashes to describe path components. The function will go down
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the structure and try to extract the required value.
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$data = {
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'a' => {
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'b' => [
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'b1',
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'b2',
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'b3',
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]
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}
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}
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$value = getpath($data, 'a/b/2', 'not_found', '/')
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=> $value = 'b3'
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a -> first hash key
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b -> second hash key
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2 -> array index starting with 0
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not_found -> (optional) will be returned if there is no value or the path did not match. Defaults to nil.
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/ -> (optional) path delimiter. Defaults to '/'.
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In addition to the required "key" argument, "getpath" accepts default
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argument. It will be returned if no value was found or a path component is
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missing. And the fourth argument can set a variable path separator.
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eos
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) do |args|
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path_lookup = lambda do |data, path, default|
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debug "Getpath: #{path.inspect} from: #{data.inspect}"
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if data.nil?
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debug "Getpath: no data, return default: #{default.inspect}"
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break default
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end
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unless path.is_a? Array
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debug "Getpath: wrong path, return default: #{default.inspect}"
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break default
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end
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unless path.any?
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debug "Getpath: value found, return data: #{data.inspect}"
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break data
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end
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unless data.is_a? Hash or data.is_a? Array
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debug "Getpath: incorrect data, return default: #{default.inspect}"
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break default
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end
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key = path.shift
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if data.is_a? Array
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begin
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key = Integer key
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rescue ArgumentError
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debug "Getpath: non-numeric path for an array, return default: #{default.inspect}"
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break default
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end
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end
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path_lookup.call data[key], path, default
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end
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data = args[0]
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path = args[1]
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default = args[2]
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separator = args[3]
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separator = '/' unless separator
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path = '' unless path
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path = path.split separator
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path_lookup.call data, path, default
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end
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end

‎spec/acceptance/getpath_spec.rb

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#! /usr/bin/env ruby -S rspec
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require 'spec_helper_acceptance'
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describe 'getpath function', :unless => UNSUPPORTED_PLATFORMS.include?(fact('operatingsystem')) do
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describe 'success' do
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it 'getpathes a value' do
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pp = <<-EOS
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$data = {
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'a' => { 'b' => 'passing'}
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}
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$tests = getpath($a, 'a/b')
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notice(inline_template('tests are <%= @tests.inspect %>'))
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EOS
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apply_manifest(pp, :catch_failures => true) do |r|
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expect(r.stdout).to match(/tests are "passing"/)
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end
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end
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end
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describe 'failure' do
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it 'uses a default value' do
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pp = <<-EOS
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$data = {
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'a' => { 'b' => 'passing'}
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}
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$tests = getpath($a, 'c/d', 'using the default value')
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notice(inline_template('tests are <%= @tests.inspect %>'))
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EOS
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apply_manifest(pp, :expect_failures => true) do |r|
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expect(r.stdout).to match(/using the default value/)
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end
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end
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it 'raises error on incorrect number of arguments' do
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pp = <<-EOS
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$o = getpath()
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EOS
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apply_manifest(pp, :expect_failures => true) do |r|
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expect(r.stderr).to match(/wrong number of arguments/i)
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end
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end
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end
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end

‎spec/functions/getpath_spec.rb

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require 'spec_helper'
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describe 'the structure function' do
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let(:scope) { PuppetlabsSpec::PuppetInternals.scope }
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it 'should exist' do
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expect(Puppet::Parser::Functions.function('getpath')).to eq 'function_getpath'
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end
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context 'single values' do
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it 'should be able to return a single value' do
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expect(scope.function_getpath(['test'])).to eq 'test'
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end
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it 'should use the default value if data is a single value and path is present' do
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expect(scope.function_getpath(['test', 'path', 'default'])).to eq 'default'
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end
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it 'should return default if there is no data' do
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expect(scope.function_getpath([nil, nil, 'default'])).to eq 'default'
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end
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it 'should be able to use data structures as default values' do
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expect(scope.function_getpath(['test', 'path', {'a' => 'a'}])).to eq({'a' => 'a'})
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end
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end
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context 'structure values' do
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it 'should be able to extracts a single hash value' do
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data = {
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'a' => '1',
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}
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expect(scope.function_getpath([data, 'a', 'default'])).to eq '1'
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end
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it 'should be able to extract a deeply nested hash value' do
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data = {
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'a' => {
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'b' => 'c'
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}
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}
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expect(scope.function_getpath([data, 'a/b', 'default'])).to eq 'c'
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end
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it 'should return the default value if the hash has no such key' do
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data = {
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'a' => '1',
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}
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expect(scope.function_getpath([data, 'b', 'default'])).to eq 'default'
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end
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it 'should return the default value if the path is not found' do
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data = {
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'a' => {
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'b' => 'c'
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}
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}
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expect(scope.function_getpath([data, 'missing', 'default'])).to eq 'default'
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end
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it 'should return the default value if the path is too long' do
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data = {
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'a' => {
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'b' => 'c'
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}
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}
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expect(scope.function_getpath([data, 'a/b/c/d', 'default'])).to eq 'default'
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end
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it 'should support an array index in the path' do
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data = {
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'a' => {
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'b' => ['b0', 'b1', 'b2', 'b3']
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}
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}
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expect(scope.function_getpath([data, 'a/b/2', 'default'])).to eq 'b2'
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end
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it 'should return the default value if an array index is not a number' do
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data = {
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'a' => {
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'b' => ['b0', 'b1', 'b2', 'b3']
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}
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}
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expect(scope.function_getpath([data, 'a/b/c', 'default'])).to eq 'default'
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end
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it 'should return the default value if and index is out of array length' do
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data = {
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'a' => {
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'b' => ['b0', 'b1', 'b2', 'b3']
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}
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}
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expect(scope.function_getpath([data, 'a/b/5', 'default'])).to eq 'default'
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end
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it 'should be able to path though both arrays and hashes' do
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data = {
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'a' => {
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'b' => [
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'b0',
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'b1',
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{
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'x' => {
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'y' => 'z'
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}
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},
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'b3'
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]
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}
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}
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expect(scope.function_getpath([data, 'a/b/2/x/y', 'default'])).to eq 'z'
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end
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it 'should be able to return "true" value' do
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data = {
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'a' => false,
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'b' => true,
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}
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expect(scope.function_getpath([data, 'b', 'default'])).to eq true
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expect(scope.function_getpath([data, 'c', true])).to eq true
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end
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it 'should be able to return "false" value' do
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data = {
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'a' => false,
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'b' => true,
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}
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expect(scope.function_getpath([data, 'a', 'default'])).to eq false
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expect(scope.function_getpath([data, 'c', false])).to eq false
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end
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it 'should return "nil" if value is not found and no default value is provided' do
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data = {
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'a' => {
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'b' => 'c'
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}
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}
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expect(scope.function_getpath([data, 'a/1'])).to eq nil
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end
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it 'should be able to use a custom path separator' do
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data = {
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'a' => {
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'b' => 'c'
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}
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}
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expect(scope.function_getpath([data, 'a::b', 'default', '::'])).to eq 'c'
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expect(scope.function_getpath([data, 'a::c', 'default', '::'])).to eq 'default'
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end
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end
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end

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