(#7316) List faces using an autoloader

Previously, calling Puppet::Interface.faces generated a
different list of face applications than those included in
Puppet::Application.available_application_names, since the former only
considered the $LOAD_PATH, and the latter used an Autoloader, which
includes gem directories and the current environment's modulepath.

From what I can tell, the method is never used, as puppet itself
accesses faces via Puppet::Interface[name, version] method. However, if
someone had called `faces` it would have excluded faces that could be
loaded via require.

lib/puppet/interface.rb

@@ -20,10 +20,9 @@ class Puppet::Interface
   include Puppet::Util
 
   class << self
-    # This is just so we can search for actions.  We only use its
-    # list of directories to search.
-    # Can't we utilize an external autoloader, or simply use the $LOAD_PATH? -pvb
+    # @deprecated
     def autoloader
+      Puppet.deprecation_warning("Puppet::Interface.autoloader is deprecated; please use Puppet::Interface#loader instead")
       @autoloader ||= Puppet::Util::Autoload.new(:application, "puppet/face")
     end
 
@@ -56,6 +55,7 @@ def face?(name, version)
 
     def [](name, version)
       unless face = Puppet::Interface::FaceCollection[name, version]
+        # REVISIT (#18042) no sense in rechecking if version == :current -- josh
         if current = Puppet::Interface::FaceCollection[name, :current]
           raise Puppet::Error, "Could not find version #{version} of #{name}"
         else

lib/puppet/interface/face_collection.rb

@@ -3,14 +3,13 @@
 module Puppet::Interface::FaceCollection
   @faces = Hash.new { |hash, key| hash[key] = {} }
 
+  @loader = Puppet::Util::Autoload.new(:application, 'puppet/face')
+
   def self.faces
     unless @loaded
       @loaded = true
-      $LOAD_PATH.each do |dir|
-        Dir.glob("#{dir}/puppet/face/*.rb").
-          collect {|f| File.basename(f, '.rb') }.
-          each {|name| self[name, :current] }
-      end
+      names = @loader.files_to_load.map {|fn| ::File.basename(fn, '.rb')}.uniq
+      names.each {|name| self[name, :current]}
     end
     @faces.keys.select {|name| @faces[name].length > 0 }
   end
@@ -58,7 +57,7 @@ def self.load_face(name, version)
     # other Ruby library that we might want to use.  --daniel 2011-04-06
     if safely_require name then
       # If we wanted :current, we need to index to find that; direct version
-      # requests just work™ as they go. --daniel 2011-04-06
+      # requests just work as they go. --daniel 2011-04-06
       if version == :current then
         # We need to find current out of this.  This is the largest version
         # number that doesn't have a dedicated on-disk file present; those
@@ -99,7 +98,7 @@ def self.load_face(name, version)
   end
 
   def self.safely_require(name, version = nil)
-    path = File.join 'puppet' ,'face', version.to_s, name.to_s
+    path = @loader.expand(version ? ::File.join(version.to_s, name.to_s) : name)
     require path
     true