Skip v7 plugins when refreshing a v6 plugin

Fixes OHAI-562

lib/ohai/system.rb

@@ -83,6 +83,13 @@ def run_plugins(safe = false, attribute_filter = nil)
         @runner.run_plugin(v6plugin)
       end
 
+      # Users who are migrating from ohai 6 may give one or more Ohai 6 plugin
+      # names as the +attribute_filter+. In this case we return early because
+      # the v7 plugin provides map will not have an entry for this plugin.
+      if attribute_filter and Array(attribute_filter).all? {|filter_item| have_v6_plugin?(filter_item) }
+        return true
+      end
+
       # Then run all the version 7 plugins
       begin
         @provides_map.all_plugins(attribute_filter).each { |plugin|
@@ -94,6 +101,10 @@ def run_plugins(safe = false, attribute_filter = nil)
       end
     end
 
+    def have_v6_plugin?(name)
+      @v6_dependency_solver.values.any? {|v6plugin| v6plugin.name == name }
+    end
+
     def pathify_v6_plugin(plugin_name)
       path_components = plugin_name.split("::")
       File.join(path_components) + ".rb"

spec/unit/system_spec.rb

@@ -517,6 +517,29 @@
   end
 
   describe "when Chef OHAI resource executes :reload action" do
+
+    when_plugins_directory "contains a v6 plugin" do
+      with_plugin("a_v6plugin.rb", <<-E)
+        plugin_data Mash.new
+        plugin_data[:foo] = :bar
+      E
+
+      before do
+        @original_config = Ohai::Config[:plugin_path]
+        Ohai::Config[:plugin_path] = [ path_to(".") ]
+      end
+
+      after do
+        Ohai::Config[:plugin_path] = @original_config
+      end
+
+      it "reloads only the v6 plugin when given a specific plugin to load" do
+        ohai.all_plugins
+        lambda { ohai.all_plugins("a_v6plugin") }.should_not raise_error
+      end
+
+    end
+
     when_plugins_directory "contains a random plugin" do
       with_plugin("random.rb", <<-E)
         Ohai.plugin(:Random) do