Add redisget() (#179)

Add the redisget() function which can get a value for a specified key
from a specified redis URL.

Gemfile

@@ -32,6 +32,8 @@ group :test do
   gem 'puppet-syntax',                                              :require => false, git: 'https://github.com/gds-operations/puppet-syntax.git'
   gem 'pry'
   gem 'rb-readline'
+  gem 'redis',                                                      :require => false
+  gem 'mock_redis',                                                 :require => false
 end
 
 group :system_tests do

LICENSE

@@ -1,4 +1,5 @@
    Copyright (C) 2012 Tom De Vylder
+   Copyright (C) 2017 Garrett Honeycutt <code@garretthoneycutt.com>
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.

README.md

@@ -67,6 +67,17 @@ With adjustments:
       failover_timeout => 30000,
     }
 
+## `redisget()` function
+
+`redisget()` takes two arguments that are strings. The first is the key
+to be looked up and the second is the URL to the Redis service.
+
+```puppet
+$version = redisget('version.myapp', 'redis://redis.example.com:6379')
+```
+
+You must have the 'redis' gem installed on your puppet master.
+
 ## Unit testing
 
 Plain RSpec:

lib/puppet/parser/functions/redisget.rb

@@ -0,0 +1,22 @@
+require 'redis'
+
+module Puppet::Parser::Functions
+  newfunction(:redisget, :type => :rvalue, :doc => <<-EOS
+    Returns the value of the key being looked up or nil if the key does not
+    exist. Takes two arguments, the first being a string value of the key to be
+    looked up and the second is the URL to the Redis service.
+    EOS
+  ) do |args|
+
+    raise(Puppet::ParseError, "redisget(): Wrong number of arguments given (#{args.size} for 2)") if args.size != 2
+
+    key = args[0]
+    url = args[1]
+
+    raise(Puppet::ParseError, "redisget(): Wrong argument type given (#{key.class} for String") if key.is_a?(String) == false
+    raise(Puppet::ParseError, "redisget(): Wrong argument type given (#{url.class} for String") if url.is_a?(String) == false
+
+    redis = Redis.new(:url => url)
+    redis.get(key)
+  end
+end

spec/functions/redisget_spec.rb

@@ -0,0 +1,55 @@
+require 'spec_helper'
+require 'mock_redis'
+require 'redis'
+
+REDIS_URL='redis://localhost:6379'
+
+describe 'redisget' do
+  context 'should return nil if key does not exist' do
+    before {
+      mr = MockRedis.new
+      Redis.stubs(:new).returns(mr)
+      mr.set('nonexistent_key', nil)
+    }
+    it { is_expected.to run.with_params('nonexistent_key', REDIS_URL).and_return('') }
+  end
+
+  context 'should return the value of the specified key' do
+    before {
+      mr = MockRedis.new
+      Redis.stubs(:new).returns(mr)
+      mr.set('key', 'value')
+    }
+    it { is_expected.to run.with_params('key', REDIS_URL).and_return('value') }
+  end
+
+  describe 'with incorrect arguments' do
+    context 'with no argument specified' do
+      it { is_expected.to run.with_params().and_raise_error(Puppet::ParseError, /wrong number of arguments/i) }
+    end
+
+    context 'with only one argument specified' do
+      it { is_expected.to run.with_params('some_key').and_raise_error(Puppet::ParseError, /wrong number of arguments/i) }
+    end
+
+    context 'with more than two arguments specified' do
+      it { is_expected.to run.with_params('too', 'many', 'args').and_raise_error(Puppet::ParseError, /wrong number of arguments/i) }
+    end
+  end
+
+  describe 'when an invalid type (non-string) is specified' do
+    before(:each) {
+      mr = MockRedis.new
+      Redis.stubs(:new).returns(mr)
+    }
+    [{ 'ha' => 'sh'}, true, 1, ['an', 'array']].each do |p|
+      context "specifing first parameter as <#{p}>" do
+        it { is_expected.to run.with_params(p, REDIS_URL).and_raise_error(Puppet::ParseError, /wrong argument type/i) }
+      end
+
+      context "specifing second parameter as <#{p}>" do
+        it { is_expected.to run.with_params('valid', p).and_raise_error(Puppet::ParseError, /wrong argument type/i) }
+      end
+    end
+  end
+end