No more use loadall() for default_profider_for() function

Change-Id: Id16605cc834e0071328bec667fcc27502a2c0f30
Closes-Bug: #1575269

deployment/puppet/l23network/lib/puppet/parser/functions/default_provider_for.rb

@@ -1,19 +1,17 @@
-
 module Puppet::Parser::Functions
   newfunction(:default_provider_for, :type => :rvalue, :doc => <<-EOS
   Get the default provider of a type
   EOS
   ) do |argv|
     type_name = argv[0]
-    fail('No type name provided!') if ! type_name
-    Puppet::Type.loadall()
-    type_name = type_name.capitalize.to_sym
-    return 'undef' if ! Puppet::Type.const_defined? type_name
-    type = Puppet::Type.const_get type_name
+    fail 'No type name provided!' unless type_name
+    type_name = type_name.to_s.downcase.to_sym
+    type = Puppet::Type.type type_name
+    return nil unless type
     provider = type.defaultprovider
-    return 'undef' if ! provider
-    rv = provider.name.to_s
-    debug("Default provider for type '#{type_name}' is a '#{rv}'.")
-    return rv
+    return nil unless provider
+    provider_name = provider.name.to_s
+    debug "default_provider_for() default provider for type '#{type_name}' is a '#{provider_name}'"
+    return provider_name
   end
 end

deployment/puppet/l23network/spec/functions/default_provider_for__spec.rb

@@ -0,0 +1,14 @@
+require 'spec_helper'
+
+describe 'default_provider_for' do
+  let(:facts) {{
+      :osfamily => 'Debian',
+      :operatingsystem => 'Ubuntu',
+      :kernel => 'Linux',
+      :l23_os => 'ubuntu',
+      :l3_fqdn_hostname => 'stupid_hostname',
+  }}
+
+  it { is_expected.not_to eq(nil) }
+  it { is_expected.to run.with_params('file').and_return('posix') }
+end