(MODULES-5679) Add a new function ifelse to match ruby's tenary operator

Author: vStone

README.md

@@ -1171,6 +1171,15 @@ For example, `hash(['a',1,'b',2,'c',3])` returns {'a'=>1,'b'=>2,'c'=>3}.
 
 *Type*: rvalue.
 
+
+#### `ifelse`
+
+Shorthand version for if-else: this maps to the ruby tenary operator.
+
+For example, `ifelse(4 > 0, 'positive', 'negative')` returns `'positive'`.
+
+*Type*: rvalue.
+
 #### `intersection`
 
 Returns an array an intersection of two.

lib/puppet/functions/ifelse.rb

@@ -0,0 +1,20 @@
+# Shorthand for bool ? true value : false value.
+#
+# @example
+#   $number_sign = ifelse($i >= 0, "positive", "negative")
+#
+Puppet::Functions.create_function(:ifelse) do
+  # @param bool Boolean condition
+  # @param iftrue Value to return if condition is true.
+  # @param iffalse Value to return if condition is false.
+  # @return Value from `$iftrue` or `$iffalse` depending on the boolean condition.
+  dispatch :ifelse do
+    param 'Boolean', :bool
+    param 'Any', :iftrue
+    param 'Any', :iffalse
+  end
+
+  def ifelse(bool, iftrue, iffalse)
+    bool ? iftrue : iffalse
+  end
+end

spec/functions/ifelse_spec.rb

@@ -0,0 +1,14 @@
+require 'spec_helper'
+
+describe 'ifelse' do
+  it { is_expected.not_to eq(nil) }
+  it { is_expected.to run.with_params.and_raise_error(ArgumentError, %r{expects 3 arguments}i) }
+  it { is_expected.to run.with_params('1').and_raise_error(ArgumentError, %r{expects 3 arguments}i) }
+
+  it { is_expected.to run.with_params('false', 'iftrue', 'iffalse').and_raise_error(ArgumentError, %r{parameter 'bool' expects a Boolean value}i) }
+
+  it { is_expected.to run.with_params(false, 'iftrue', 'iffalse').and_return('iffalse') }
+  it { is_expected.to run.with_params(true, 'iftrue', 'iffalse').and_return('iftrue') }
+  it { is_expected.to run.with_params(true, :undef, 'iffalse').and_return(:undef) }
+  it { is_expected.to run.with_params(true, nil, 'iffalse').and_return(nil) }
+end