dnstap: add print_config functions

Add a new function to print function lines.  this is similar to the ruby
function in unbound.conf.erb and should allow us to move the other
templates to epp.

Author: b4ldr

REFERENCE.md

@@ -16,6 +16,10 @@
 * [`unbound::record`](#unbound--record): Create an unbound static DNS record override
 * [`unbound::stub`](#unbound--stub): Create an unbound stub zone for caching upstream name resolvers
 
+### Functions
+
+* [`unbound::print_config`](#unbound--print_config): Print a configuration value if it is defined and the version is supported
+
 ### Data types
 
 * [`Unbound::Access_control`](#Unbound--Access_control): custom type for access control lists
@@ -2341,6 +2345,38 @@ Name of the unbound config file
 
 Default value: `undef`
 
+## Functions
+
+### <a name="unbound--print_config"></a>`unbound::print_config`
+
+Type: Puppet Language
+
+Print a configuration value if it is defined and the version is supported
+
+#### `unbound::print_config(String[1] $name, Optional[Variant[Boolean, Integer, String, Array[String, 1]]] $value = undef, Optional[String[1]] $version = undef)`
+
+The unbound::print_config function.
+
+Returns: `String` the config item as a string or an empty string if the version is not supported
+
+##### `name`
+
+Data type: `String[1]`
+
+the config item name
+
+##### `value`
+
+Data type: `Optional[Variant[Boolean, Integer, String, Array[String, 1]]]`
+
+the config item value
+
+##### `version`
+
+Data type: `Optional[String[1]]`
+
+the version when the config item was introduced
+
 ## Data types
 
 ### <a name="Unbound--Access_control"></a>`Unbound::Access_control`

functions/print_config.pp

@@ -0,0 +1,21 @@
+# @summary Print a configuration value if it is defined and the version is supported
+# @param name the config item name
+# @param value the config item value
+# @param version the version when the config item was introduced
+# @return the config item as a string or an empty string if the version is not supported
+function unbound::print_config (
+  String[1]                                                     $name,
+  Optional[Variant[Boolean, Integer, String, Array[String, 1]]] $value   = undef,
+  Optional[String[1]]                                           $version = undef,
+) >> String {
+  $unbound_version = $facts['unbound_version'].lest || { '0.a' }
+  if ($value =~ Undef or ($version =~ NotUndef and versioncmp($unbound_version, $version) < 0)) {
+    return ''
+  }
+  $value ? {
+    String  => "  ${name}: \"${value}\"",
+    Integer => "  ${name}: ${value}",
+    Boolean => "  ${name}: ${value.bool2str('yes', 'no')}",
+    Array   => $value.map |$v| { "  ${name}: \"${v}\"" }.join("\n"),
+  }
+}

spec/functions/print_config_spec.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'unbound::print_config' do
+  it { is_expected.to run.with_params('string_name', 'string_value').and_return('  string_name: "string_value"') }
+  it { is_expected.to run.with_params('int_name', 42).and_return('  int_name: 42') }
+  it { is_expected.to run.with_params('true_name', true).and_return('  true_name: yes') }
+  it { is_expected.to run.with_params('false_name', false).and_return('  false_name: no') }
+
+  it do
+    is_expected.to run.with_params('list_name', %w[value1 value2]).
+      and_return("  list_name: \"value1\"\n  list_name: \"value2\"")
+  end
+
+  context 'with version' do
+    let(:facts) { { 'unbound_version' => '1.21.0' } }
+
+    it { is_expected.to run.with_params('supported', 42, '1.11.0').and_return('  supported: 42') }
+    it { is_expected.to run.with_params('supported', 42, '1.21.0').and_return('  supported: 42') }
+    it { is_expected.to run.with_params('unsupported', 42, '1.22.0').and_return('') }
+  end
+end