Added the regexpescape function.

lib/puppet/parser/functions/regexpescape.rb

@@ -0,0 +1,31 @@
+#
+#  regexpescape.rb
+#
+module Puppet::Parser::Functions
+  newfunction(:regexpescape, :type => :rvalue, :doc => <<-EOS
+    Regexp escape a string or array of strings.
+    Requires either a single string or an array as an input.
+    EOS
+  ) do |arguments| # rubocop:disable Style/ClosingParenthesisIndentation
+    raise(Puppet::ParseError, 'regexpescape(): Wrong number of arguments ' \
+      "given (#{arguments.size} for 1)") if arguments.empty?
+
+    value = arguments[0]
+
+    unless value.is_a?(Array) || value.is_a?(String)
+      raise(Puppet::ParseError, 'regexpescape(): Requires either ' \
+        'array or string to work with')
+    end
+
+    result = if value.is_a?(Array)
+               # Numbers in Puppet are often string-encoded which is troublesome ...
+               value.collect { |i| i.is_a?(String) ? Regexp.escape(i) : i }
+             else
+               Regexp.escape(value)
+             end
+
+    return result
+  end
+end
+
+# vim: set ts=2 sw=2 et :

spec/functions/regexpescape_spec.rb

@@ -0,0 +1,36 @@
+require 'spec_helper'
+
+describe 'regexpescape' do
+  describe 'signature validation' do
+    it { is_expected.not_to eq(nil) }
+    it { is_expected.to run.with_params().and_raise_error(Puppet::ParseError, /wrong number of arguments/i) }
+    it {
+      pending("Current implementation ignores parameters after the first.")
+      is_expected.to run.with_params('', '').and_raise_error(Puppet::ParseError, /wrong number of arguments/i)
+    }
+    it { is_expected.to run.with_params(1).and_raise_error(Puppet::ParseError, /Requires either array or string to work/) }
+    it { is_expected.to run.with_params({}).and_raise_error(Puppet::ParseError, /Requires either array or string to work/) }
+    it { is_expected.to run.with_params(true).and_raise_error(Puppet::ParseError, /Requires either array or string to work/) }
+  end
+
+  describe 'handling normal strings' do
+    it 'should call ruby\'s Regexp.escape function' do
+      Regexp.expects(:escape).with('regexp_string').returns('escaped_regexp_string').once
+      is_expected.to run.with_params('regexp_string').and_return('escaped_regexp_string')
+    end
+  end
+
+  describe 'handling classes derived from String' do
+    it 'should call ruby\'s Regexp.escape function' do
+      regexp_string = AlsoString.new('regexp_string')
+      Regexp.expects(:escape).with(regexp_string).returns('escaped_regexp_string').once
+      is_expected.to run.with_params(regexp_string).and_return("escaped_regexp_string")
+    end
+  end
+
+  describe 'strings in arrays handling' do
+    it { is_expected.to run.with_params([]).and_return([]) }
+    it { is_expected.to run.with_params(['one*', "two"]).and_return(['one\*', "two"]) }
+    it { is_expected.to run.with_params(['one*', 1, true, {}, "two"]).and_return(['one\*', 1, true, {}, "two"]) }
+  end
+end