Puppet function to list the files in a module's 'files' directory

get_module_files.rb

#
# get_module_files.rb
#
module Puppet::Parser::Functions
  newfunction(:get_module_files, :type => :rvalue, :doc => <<-DOC
    Returns an array of relative files names for a given module and optional
    sub directory. Do not include 'files' in the optional relative path as it
    is assumed.
    Returns an empty array if no files are found.
    Errors if the requested module does not exist.

    Example:
      With a files directory of:
         files/
           foo.sh
           bar.txt
           default-configs/
             file1.txt
             file2.xml

      get_module_files($module_name)
        Returns: ['foo.sh', 'bar.txt', 'default-configs/file1.txt', 'default-configs/file2.xml']

      get_module_files("${module_name}/default-configs")
        Returns: ['file1.txt', 'file2.xml']
  DOC
             ) do |args|
    raise(Puppet::ParseError, 'get_module_files(): Wrong number of arguments, expects one') unless args.size == 1

    # Parse the module name and optional sub directory out of the arguments.
    module_name, *sub_directory = args[0].split('/')

    # Ask the compiler for the path to the module.
    module_path = Puppet::Module.find(module_name, compiler.environment.to_s)
    raise(Puppet::ParseError, "Could not find module #{module_name} in environment #{compiler.environment}") unless module_path

    # Build the abosolute path of the directory to search through.
    # Uses splat and compact to account for a possibly nil sub_directory.
    paths = [module_path.path, 'files', sub_directory].flatten.compact
    search_path = File.join(*paths)

    # Search for files.
    files = Dir[File.join(search_path,'**','*')]
      .select  { |e| File.file?(e) }                 # Select only real files, not directories.
      .collect { |f| f.sub("#{search_path}/", '') }  # Strip the module path out of the result.

    # Return the array of found files.
    files
  end
end

Or just use functions from stdlib:

$module_path = get_module_path($module_name)
$files = glob("${module_path}/files/**/*").regsubst("${module_path}/files/",'')