1 files changed, 49 insertions, 3 deletions

diff --git a/lib/chef/knife/core/subcommand_loader.rb b/lib/chef/knife/core/subcommand_loader.rb
index f18bc6619e..0489c726b3 100644
--- a/lib/chef/knife/core/subcommand_loader.rb
+++ b/lib/chef/knife/core/subcommand_loader.rb
@@ -60,9 +60,13 @@ class Chef
       # subcommand loader has been modified to load the plugins by using Kernel.load
       # with the absolute path.
       def gem_and_builtin_subcommands
-        # search all gems for chef/knife/*.rb
-        require 'rubygems'
-        find_subcommands_via_rubygems
+        if have_plugin_manifest?
+          find_subcommands_via_manifest
+        else
+          # search all gems for chef/knife/*.rb
+          require 'rubygems'
+          find_subcommands_via_rubygems
+        end
       rescue LoadError
         find_subcommands_via_dirglob
       end
@@ -71,6 +75,36 @@ class Chef
         @subcommand_files ||= (gem_and_builtin_subcommands.values + site_subcommands).flatten.uniq
       end
 
+      # If the user has created a ~/.chef/plugin_manifest.json file, we'll use
+      # that instead of inspecting the on-system gems to find the plugins. The
+      # file format is expected to look like:
+      #
+      #   { "plugins": {
+      #       "knife-ec2": {
+      #         "paths": [
+      #           "/home/alice/.rubymanagerthing/gems/knife-ec2-x.y.z/lib/chef/knife/ec2_server_create.rb",
+      #           "/home/alice/.rubymanagerthing/gems/knife-ec2-x.y.z/lib/chef/knife/ec2_server_delete.rb"
+      #         ]
+      #       }
+      #     }
+      #   }
+      #
+      # Extraneous content in this file is ignored. This intentional so that we
+      # can adapt the file format for potential behavior changes to knife in
+      # the future.
+      def find_subcommands_via_manifest
+        # Format of subcommand_files is "relative_path" (something you can
+        # Kernel.require()) => full_path. The relative path isn't used
+        # currently, so we just map full_path => full_path.
+        subcommand_files = {}
+        plugin_manifest["plugins"].each do |plugin_name, plugin_manifest|
+          plugin_manifest["paths"].each do |cmd_path|
+            subcommand_files[cmd_path] = cmd_path
+          end
+        end
+        subcommand_files.merge(find_subcommands_via_dirglob)
+      end
+
       def find_subcommands_via_dirglob
         # The "require paths" of the core knife subcommands bundled with chef
         files = Dir[File.expand_path('../../../knife/*.rb', __FILE__)]
@@ -93,6 +127,18 @@ class Chef
         subcommand_files.merge(find_subcommands_via_dirglob)
       end
 
+      def have_plugin_manifest?
+        ENV["HOME"] && File.exist?(plugin_manifest_path)
+      end
+
+      def plugin_manifest
+        Chef::JSONCompat.from_json(File.read(plugin_manifest_path))
+      end
+
+      def plugin_manifest_path
+        File.join(ENV['HOME'], '.chef', 'plugin_manifest.json')
+      end
+
       private
 
       def find_files_latest_gems(glob, check_load_path=true)