Utility to handle IPv6 address brackets.

This add the function normalize_ip_for_uri to the parser.  It encloses
into brackets any valid IPv6 address thrown at it.

Change-Id: I093dd5a4e6294e20761cb3d33373652eeadeac36
Closes-bug: 1531960

lib/puppet/parser/functions/normalize_ip_for_uri.rb

@@ -0,0 +1,31 @@
+require 'ipaddr'
+
+module Puppet::Parser::Functions
+  newfunction(:normalize_ip_for_uri,
+              :type => :rvalue,
+              :arity => 1,
+              :doc => <<-EOD
+    Add brackets if the argument is an IPv6 address.
+    Returns the argument untouched otherwise.
+    CAUTION: this code "fails" when the user is passing
+    an IPv6 address with the port in it without the
+    brackets: 2001::1:8080, to specify address 2001::1
+    and port 8080.  This code will change it to
+    [2001::1:8080] as it's a valid ip address.  This
+    shouldn't be an issue in most cases.
+    EOD
+  ) do |args|
+    ip = args[0]
+    begin
+      if IPAddr.new(ip).ipv6?
+        unless ip.match(/\[.+\]/)
+          Puppet.debug("IP #{ip} is changed to [#{ip}]")
+          ip = "[#{ip}]"
+        end
+      end
+    rescue ArgumentError => e
+      # ignore it
+    end
+    return ip
+  end
+end

spec/functions/normalize_ip_for_uri_spec.rb

@@ -0,0 +1,13 @@
+require 'spec_helper'
+
+describe 'normalize_ip_for_uri' do
+  it { should run.with_params(false).and_return(false)}
+  it { should run.with_params('not_an_ip').and_return('not_an_ip')}
+  it { should run.with_params('127.0.0.1').and_return('127.0.0.1')}
+  it { should run.with_params('::1').and_return('[::1]')}
+  it { should run.with_params('[2001::01]').and_return('[2001::01]')}
+  it do
+    is_expected.to run.with_params('one', 'two')
+      .and_raise_error(ArgumentError, /Wrong number of arguments/)
+  end
+end