From 48c29a3a729f43334a890142dbba9584791bc99e Mon Sep 17 00:00:00 2001
From: Thom May <thom@chef.io>
Date: Fri, 16 Feb 2018 16:45:06 +0000
Subject: Support optional plugins

Some plugins are useful enough to ship in Ohai, but should be off by
default. Those plugins can be (and are) marked as optional. Implements
RFC 103

Signed-off-by: Thom May <thom@chef.io>
---
 lib/ohai/config.rb                 |  4 ++++
 lib/ohai/dsl/plugin.rb             | 11 ++---------
 lib/ohai/dsl/plugin/versionvii.rb  | 12 ++++++++++++
 lib/ohai/plugins/linux/lspci.rb    |  1 +
 lib/ohai/plugins/linux/sessions.rb |  1 +
 lib/ohai/plugins/passwd.rb         |  1 +
 lib/ohai/runner.rb                 |  4 ++++
 spec/unit/system_spec.rb           | 33 +++++++++++++++++++++++++++++++++
 8 files changed, 58 insertions(+), 9 deletions(-)

diff --git a/lib/ohai/config.rb b/lib/ohai/config.rb
index aa73900b..9c24a7bf 100644
--- a/lib/ohai/config.rb
+++ b/lib/ohai/config.rb
@@ -36,6 +36,10 @@ module Ohai
       default :plugin, Ohai::PluginConfig.new { |h, k| h[k] = Ohai::PluginConfig.new }
       default :plugin_path, [ File.expand_path(File.join(File.dirname(__FILE__), "plugins")), ChefConfig::Config.platform_specific_path("/etc/chef/ohai/plugins") ]
       default :critical_plugins, []
+      # causes all optional plugins to be run.
+      default :run_all_plugins, false
+      # optional plugins are the set of plugins that are marked optional but you wish to run.
+      default :optional_plugins, []
     end
   end
 
diff --git a/lib/ohai/dsl/plugin.rb b/lib/ohai/dsl/plugin.rb
index a0d8c150..96867780 100644
--- a/lib/ohai/dsl/plugin.rb
+++ b/lib/ohai/dsl/plugin.rb
@@ -32,15 +32,8 @@ module Ohai
       name.is_a?(Symbol) && name.to_s.match(/^[^A-Z]|_/).nil?
     end
 
-    # dealing with ruby 1.8
-    if Module.method(:const_defined?).arity == 1
-      def self.strict_const_defined?(const)
-        const_defined?(const)
-      end
-    else
-      def self.strict_const_defined?(const)
-        const_defined?(const, false)
-      end
+    def self.strict_const_defined?(const)
+      const_defined?(const, false)
     end
   end
 
diff --git a/lib/ohai/dsl/plugin/versionvii.rb b/lib/ohai/dsl/plugin/versionvii.rb
index cd8dc13c..75cc65c0 100644
--- a/lib/ohai/dsl/plugin/versionvii.rb
+++ b/lib/ohai/dsl/plugin/versionvii.rb
@@ -66,6 +66,14 @@ module Ohai
           end
         end
 
+        def self.optional(opt = true)
+          @optional = opt
+        end
+
+        def self.optional?
+          !!@optional
+        end
+
         def self.collect_data(platform = :default, *other_platforms, &block)
           [platform, other_platforms].flatten.each do |plat|
             if data_collector.has_key?(plat)
@@ -93,6 +101,10 @@ module Ohai
           end
         end
 
+        def optional?
+          self.class.optional?
+        end
+
         def provides(*paths)
           Ohai::Log.warn("[UNSUPPORTED OPERATION] \'provides\' is no longer supported in a \'collect_data\' context. Please specify \'provides\' before collecting plugin data. Ignoring command \'provides #{paths.join(", ")}")
         end
diff --git a/lib/ohai/plugins/linux/lspci.rb b/lib/ohai/plugins/linux/lspci.rb
index 9e3b2ac3..fa03747e 100644
--- a/lib/ohai/plugins/linux/lspci.rb
+++ b/lib/ohai/plugins/linux/lspci.rb
@@ -20,6 +20,7 @@
 Ohai.plugin(:Lspci) do
   depends "platform"
   provides "pci"
+  optional true
 
   collect_data(:linux) do
     devices = Mash.new
diff --git a/lib/ohai/plugins/linux/sessions.rb b/lib/ohai/plugins/linux/sessions.rb
index 7fb2b5ae..2d53813e 100644
--- a/lib/ohai/plugins/linux/sessions.rb
+++ b/lib/ohai/plugins/linux/sessions.rb
@@ -18,6 +18,7 @@
 
 Ohai.plugin(:Sessions) do
   provides "sessions/by_session", "sessions/by_user"
+  optional true
 
   collect_data(:linux) do
     loginctl_path = which("loginctl")
diff --git a/lib/ohai/plugins/passwd.rb b/lib/ohai/plugins/passwd.rb
index 2539fa26..824153ae 100644
--- a/lib/ohai/plugins/passwd.rb
+++ b/lib/ohai/plugins/passwd.rb
@@ -2,6 +2,7 @@
 Ohai.plugin(:Passwd) do
   require "etc"
   provides "etc", "current_user"
+  optional true
 
   def fix_encoding(str)
     str.force_encoding(Encoding.default_external) if str.respond_to?(:force_encoding)
diff --git a/lib/ohai/runner.rb b/lib/ohai/runner.rb
index ba3985dc..6f623d38 100644
--- a/lib/ohai/runner.rb
+++ b/lib/ohai/runner.rb
@@ -59,6 +59,10 @@ module Ohai
     end
 
     def run_v7_plugin(plugin)
+      return true if plugin.optional? &&
+          !Ohai.config[:run_all_plugins] &&
+          !Ohai.config[:optional_plugins].include?(plugin.name)
+
       visited = [ plugin ]
       until visited.empty?
         next_plugin = visited.pop
diff --git a/spec/unit/system_spec.rb b/spec/unit/system_spec.rb
index 57341e76..e0631cd8 100644
--- a/spec/unit/system_spec.rb
+++ b/spec/unit/system_spec.rb
@@ -175,6 +175,17 @@ Ohai.plugin(:Fails) do
     fail 'thing'
   end
 end
+EOF
+
+      with_plugin("optional.rb", <<EOF)
+Ohai.plugin(:Optional) do
+  provides 'optional'
+  optional true
+
+  collect_data(:default) do
+    optional("canteloupe")
+  end
+end
 EOF
 
       it "should collect data from all the plugins" do
@@ -230,6 +241,28 @@ EOF
                                                      "The following Ohai plugins marked as critical failed: [:Fails]. Failing Chef run.")
         end
       end
+
+      describe "when using :optional_plugins" do
+        it "should not run optional plugins by default" do
+          Ohai.config[:plugin_path] = [ path_to(".") ]
+          ohai.all_plugins
+          expect(ohai.data[:optional]).to be_nil
+        end
+
+        it "should run optional plugins when specifically enabled" do
+          Ohai.config[:optional_plugins] = [ :Optional ]
+          Ohai.config[:plugin_path] = [ path_to(".") ]
+          ohai.all_plugins
+          expect(ohai.data[:optional]).to eq("canteloupe")
+        end
+
+        it "should run optional plugins when all plugins are enabled" do
+          Ohai.config[:run_all_plugins] = true
+          Ohai.config[:plugin_path] = [ path_to(".") ]
+          ohai.all_plugins
+          expect(ohai.data[:optional]).to eq("canteloupe")
+        end
+      end
     end
   end
 
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