# Test whether a given class or definition is defined
Puppet::Parser::Functions::newfunction(:defined, :type => :rvalue, :arity => -2, :doc => "Determine whether
  a given class or resource type is defined. This function can also determine whether a
  specific resource has been declared, or whether a variable has been assigned a value
  (including undef...as opposed to never having been assigned anything). Returns true
  or false. Accepts class names, type names, resource references, and variable
  reference strings of the form '$name'.  When more than one argument is
  supplied, defined() returns true if any are defined.

  The `defined` function checks both native and defined types, including types
  provided as plugins via modules. Types and classes are both checked using their names:

      defined(\"file\")
      defined(\"customtype\")
      defined(\"foo\")
      defined(\"foo::bar\")
      defined(\'$name\')

  Resource declarations are checked using resource references, e.g.
  `defined( File['/tmp/myfile'] )`. Checking whether a given resource
  has been declared is, unfortunately, dependent on the parse order of
  the configuration, and the following code will not work:

      if defined(File['/tmp/foo']) {
          notify { \"This configuration includes the /tmp/foo file.\":}
      }
      file { \"/tmp/foo\":
          ensure => present,
      }

  However, this order requirement refers to parse order only, and ordering of
  resources in the configuration graph (e.g. with `before` or `require`) does not
  affect the behavior of `defined`.

  If the future parser is in effect, you may also search using types:

      defined(Resource[\'file\',\'/some/file\'])
      defined(File[\'/some/file\'])
      defined(Class[\'foo\'])

  The `defined` function does not answer if 4.x data types (e.g. `Integer`) are defined. If
  given the string 'integer' the result is false, and if given a non CatalogEntry type,
  an error is raised.

  The rules for asking for undef, empty strings, and the main class are different from 3.x
  (non future parser) and 4.x (with future parser or in Puppet 4.0.0 and later):

      defined('')     # 3.x => true, 4.x => false
      defined(undef)  # 3.x => true, 4.x => error
      defined('main') # 3.x => false, 4.x => true

  With the future parser, it is also possible to ask specifically if a name is
  a resource type (built in or defined), or a class, by giving its type:

      defined(Type[Class['foo']])
      defined(Type[Resource['foo']])

  Which is different from asking:

      defined('foo')

  Since the later returns true if 'foo' is either a class, a built-in resource type, or a user defined
  resource type, and a specific request like `Type[Class['foo']]` only returns true if `'foo'` is a class.

 - Since 2.7.0
 - Since 3.6.0 variable reference and future parser types
 - Since 3.8.1 type specific requests with future parser") do |vals|
    vals = [vals] unless vals.is_a?(Array)
    vals.any? do |val|
      case val
      when String
        if m = /^\$(.+)$/.match(val)
          exist?(m[1])
        else
          find_resource_type(val) or find_definition(val) or find_hostclass(val)
        end
      when Puppet::Resource
        compiler.findresource(val.type, val.title)
      else
        if Puppet.future_parser?
          case val
          when Puppet::Pops::Types::PResourceType
            raise ArgumentError, "The given resource type is a reference to all kind of types" if val.type_name.nil?
            if val.title.nil?
              find_builtin_resource_type(val.type_name) || find_definition(val.type_name)
            else
              compiler.findresource(val.type_name, val.title)
            end
          when Puppet::Pops::Types::PHostClassType
            raise  ArgumentError, "The given class type is a reference to all classes" if val.class_name.nil?
            find_hostclass(val.class_name)
          end
        else
          raise ArgumentError, "Invalid argument of type '#{val.class}' to 'defined'"
        end
      end
    end
end