Rewrite fqdn_rand_string() as a Puppet 4.x function

The 3.x function rely on is_integer() which is deprecated.  Rewrite it
using the more modern puppet 4.x function to rely on data types for
better parameters validation.

Author: smortex

lib/puppet/functions/fqdn_rand_string.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+# @summary
+#   Generates a random alphanumeric string. Combining the `$fqdn` fact and an
+#   optional seed for repeatable randomness.
+#
+# Optionally, you can specify a character set for the function (defaults to alphanumeric).
+Puppet::Functions.create_function(:fqdn_rand_string) do
+  # @param length The length of the resulting string.
+  # @param charset The character set to use.
+  # @param The seed for repeatable randomness.
+  #
+  # @return [String]
+  #
+  # @example Example Usage:
+  #   fqdn_rand_string(10)
+  #   fqdn_rand_string(10, 'ABCDEF!@$%^')
+  #   fqdn_rand_string(10, '', 'custom seed')
+  dispatch :fqdn_rand_string do
+    param 'Integer[1]', :length
+    optional_param 'String', :charset
+    optional_param 'String', :seed
+  end
+
+  def fqdn_rand_string(length, charset = '', seed = nil)
+    charset = charset.chars.to_a
+
+    charset = (0..9).map { |i| i.to_s } + ('A'..'Z').to_a + ('a'..'z').to_a if charset.empty?
+
+    rand_string = ''
+    length.times do |current|
+      rand_string += charset[call_function('fqdn_rand', charset.size, [seed, (current + 1).to_s].compact.join(':')).to_i]
+    end
+
+    rand_string
+  end
+end

lib/puppet/parser/functions/fqdn_rand_string.rb

@@ -6,20 +6,20 @@
   let(:default_charset) { %r{\A[a-zA-Z0-9]{100}\z} }
 
   it { is_expected.not_to eq(nil) }
-  it { is_expected.to run.with_params.and_raise_error(ArgumentError, %r{wrong number of arguments}i) }
-  it { is_expected.to run.with_params(0).and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
-  it { is_expected.to run.with_params(1.5).and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
-  it { is_expected.to run.with_params(-10).and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
-  it { is_expected.to run.with_params('-10').and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
-  it { is_expected.to run.with_params('string').and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
-  it { is_expected.to run.with_params([]).and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
-  it { is_expected.to run.with_params({}).and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
-  it { is_expected.to run.with_params(1, 1).and_raise_error(ArgumentError, %r{second argument must be undef or a string}) }
-  it { is_expected.to run.with_params(1, []).and_raise_error(ArgumentError, %r{second argument must be undef or a string}) }
-  it { is_expected.to run.with_params(1, {}).and_raise_error(ArgumentError, %r{second argument must be undef or a string}) }
+  it { is_expected.to run.with_params.and_raise_error(ArgumentError, %r{expects between 1 and 3 arguments, got none}i) }
+  it { is_expected.to run.with_params(0).and_raise_error(ArgumentError, %r{parameter 'length' expects an Integer\[1\] value, got Integer\[0, 0\]}) }
+  it { is_expected.to run.with_params(1.5).and_raise_error(ArgumentError, %r{parameter 'length' expects an Integer\ value, got Float}) }
+  it { is_expected.to run.with_params(-10).and_raise_error(ArgumentError, %r{parameter 'length' expects an Integer\[1\] value, got Integer\[-10, -10\]}) }
+  it { is_expected.to run.with_params('-10').and_raise_error(ArgumentError, %r{parameter 'length' expects an Integer\ value, got String}) }
+  it { is_expected.to run.with_params('string').and_raise_error(ArgumentError, %r{parameter 'length' expects an Integer\ value, got String}) }
+  it { is_expected.to run.with_params([]).and_raise_error(ArgumentError, %r{parameter 'length' expects an Integer value, got Array}) }
+  it { is_expected.to run.with_params({}).and_raise_error(ArgumentError, %r{parameter 'length' expects an Integer value, got Hash}) }
+  it { is_expected.to run.with_params(1, 1).and_raise_error(ArgumentError, %r{parameter 'charset' expects a String value, got Integer}) }
+  it { is_expected.to run.with_params(1, []).and_raise_error(ArgumentError, %r{parameter 'charset' expects a String value, got Array}) }
+  it { is_expected.to run.with_params(1, {}).and_raise_error(ArgumentError, %r{parameter 'charset' expects a String value, got Hash}) }
+  it { is_expected.to run.with_params('100').and_raise_error(ArgumentError, %r{parameter 'length' expects an Integer value, got String}) }
+  it { is_expected.to run.with_params(100, nil).and_raise_error(ArgumentError, %r{parameter 'charset' expects a String value, got Undef}) }
   it { is_expected.to run.with_params(100).and_return(default_charset) }
-  it { is_expected.to run.with_params('100').and_return(default_charset) }
-  it { is_expected.to run.with_params(100, nil).and_return(default_charset) }
   it { is_expected.to run.with_params(100, '').and_return(default_charset) }
   it { is_expected.to run.with_params(100, 'a').and_return(%r{\Aa{100}\z}) }
   it { is_expected.to run.with_params(100, 'ab').and_return(%r{\A[ab]{100}\z}) }