From 25daca8f23da3f40d5e6d5e42c36f31d5eceb166 Mon Sep 17 00:00:00 2001
From: Robin Ward <robin.ward@gmail.com>
Date: Wed, 4 Feb 2015 16:23:39 -0500
Subject: [PATCH] Helpers for plugins to support enabling/disabling

---
 .../discourse/helpers/plugin-outlet.js.es6    | 34 ++++++++----
 app/controllers/application_controller.rb     | 10 ++++
 app/serializers/site_serializer.rb            |  7 ++-
 lib/discourse.rb                              |  5 ++
 lib/plugin/instance.rb                        | 39 ++++++++++++--
 spec/components/plugin/instance_spec.rb       | 54 +++++++++++++++++++
 6 files changed, 135 insertions(+), 14 deletions(-)

diff --git a/app/assets/javascripts/discourse/helpers/plugin-outlet.js.es6 b/app/assets/javascripts/discourse/helpers/plugin-outlet.js.es6
index 42802f8bcee..a209513aefd 100644
--- a/app/assets/javascripts/discourse/helpers/plugin-outlet.js.es6
+++ b/app/assets/javascripts/discourse/helpers/plugin-outlet.js.es6
@@ -39,18 +39,35 @@
        Nobody says hello :'(
      {{/plugin-outlet}}
    ```
+
+   ## Disabling
+
+   If a plugin returns a disabled status, the outlets will not be wired up for it.
+   The list of disabled plugins is returned via the `Site` singleton.
+
 **/
 
 var _connectorCache;
 
 function findOutlets(collection, callback) {
-  Ember.keys(collection).forEach(function(i) {
-    if (i.indexOf("/connectors/") !== -1) {
-      var segments = i.split("/"),
+
+  var disabledPlugins = Discourse.Site.currentProp('disabled_plugins') || [];
+
+  Ember.keys(collection).forEach(function(res) {
+    if (res.indexOf("/connectors/") !== -1) {
+      // Skip any disabled plugins
+      for (var i=0; i<disabledPlugins.length; i++) {
+        if (res.indexOf("/" + disabledPlugins[i] + "/") !== -1) {
+          return;
+        }
+      }
+
+      var segments = res.split("/"),
           outletName = segments[segments.length-2],
           uniqueName = segments[segments.length-1];
 
-      callback(outletName, i, uniqueName);
+
+      callback(outletName, res, uniqueName);
     }
   });
 }
@@ -59,18 +76,18 @@ function buildConnectorCache() {
   _connectorCache = {};
 
   var uniqueViews = {};
-  findOutlets(requirejs._eak_seen, function(outletName, idx, uniqueName) {
+  findOutlets(requirejs._eak_seen, function(outletName, resource, uniqueName) {
     _connectorCache[outletName] = _connectorCache[outletName] || [];
 
-    var viewClass = require(idx, null, null, true).default;
+    var viewClass = require(resource, null, null, true).default;
     uniqueViews[uniqueName] = viewClass;
     _connectorCache[outletName].pushObject(viewClass);
   });
 
-  findOutlets(Ember.TEMPLATES, function(outletName, idx, uniqueName) {
+  findOutlets(Ember.TEMPLATES, function(outletName, resource, uniqueName) {
     _connectorCache[outletName] = _connectorCache[outletName] || [];
 
-    var mixin = {templateName: idx.replace('javascripts/', '')},
+    var mixin = {templateName: resource.replace('javascripts/', '')},
         viewClass = uniqueViews[uniqueName];
 
     if (viewClass) {
@@ -81,7 +98,6 @@ function buildConnectorCache() {
     }
     _connectorCache[outletName].pushObject(viewClass.extend(mixin));
   });
-
 }
 
 export default function(connectionName, options) {
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index cb898bbb68b..4ca9107d014 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -130,6 +130,16 @@ class ApplicationController < ActionController::Base
     end
   end
 
+  class PluginDisabled < Exception; end
+
+  # If a controller requires a plugin, it will raise an exception if that plugin is
+  # disabled. This allows plugins to be disabled programatically.
+  def self.requires_plugin(plugin_name)
+    before_filter do
+      raise PluginDisabled.new if Discourse.disabled_plugin_names.include?(plugin_name)
+    end
+  end
+
   def set_current_user_for_logs
     if current_user
       Logster.add_to_env(request.env,"username",current_user.username)
diff --git a/app/serializers/site_serializer.rb b/app/serializers/site_serializer.rb
index 7d0dde56f09..3d2149e8ef7 100644
--- a/app/serializers/site_serializer.rb
+++ b/app/serializers/site_serializer.rb
@@ -9,7 +9,8 @@ class SiteSerializer < ApplicationSerializer
              :top_menu_items,
              :anonymous_top_menu_items,
              :uncategorized_category_id, # this is hidden so putting it here
-             :is_readonly
+             :is_readonly,
+             :disabled_plugins
 
   has_many :categories, serializer: BasicCategorySerializer, embed: :objects
   has_many :post_action_types, embed: :objects
@@ -51,4 +52,8 @@ class SiteSerializer < ApplicationSerializer
     Discourse.readonly_mode?
   end
 
+  def disabled_plugins
+    Discourse.disabled_plugin_names
+  end
+
 end
diff --git a/lib/discourse.rb b/lib/discourse.rb
index 8030079a398..0e299758e2e 100644
--- a/lib/discourse.rb
+++ b/lib/discourse.rb
@@ -84,6 +84,11 @@ module Discourse
     @plugins.each { |plugin| plugin.activate! }
   end
 
+  def self.disabled_plugin_names
+    return [] if @plugins.blank?
+    @plugins.select {|p| !p.enabled?}.map(&:name)
+  end
+
   def self.plugins
     @plugins
   end
diff --git a/lib/plugin/instance.rb b/lib/plugin/instance.rb
index 92bafc7b2af..cb34bca3b67 100644
--- a/lib/plugin/instance.rb
+++ b/lib/plugin/instance.rb
@@ -39,15 +39,35 @@ class Plugin::Instance
     end
   end
 
-  def name
-    metadata.name
+  def enabled?
+    return @enabled_site_setting ? SiteSetting.send(@enabled_site_setting) : true
   end
 
+  delegate :name, to: :metadata
+
   def add_to_serializer(serializer, attr, &block)
     klass = "#{serializer.to_s.classify}Serializer".constantize
-
     klass.attributes(attr)
     klass.send(:define_method, attr, &block)
+
+    # Don't include serialized methods if the plugin is disabled
+    plugin = self
+    klass.send(:define_method, "include_#{attr}?") do
+      plugin.enabled?
+    end
+  end
+
+  # Extend a class but check that the plugin is enabled
+  def add_to_class(klass, attr, &block)
+    klass = klass.to_s.classify.constantize
+
+    hidden_method_name = "#{attr}_without_enable_check".to_sym
+    klass.send(:define_method, hidden_method_name, &block)
+
+    plugin = self
+    klass.send(:define_method, attr) do |*args|
+      send(hidden_method_name, *args) if plugin.enabled?
+    end
   end
 
   # will make sure all the assets this plugin needs are registered
@@ -95,13 +115,20 @@ class Plugin::Instance
     initializers << block
   end
 
+  # A proxy to `DiscourseEvent.on` which does nothing if the plugin is disabled
+  def on(event_name, &block)
+    DiscourseEvent.on(event_name) do |*args|
+      block.call(*args) if enabled?
+    end
+  end
+
   def notify_after_initialize
     color_schemes.each do |c|
       ColorScheme.create_from_base(name: c[:name], colors: c[:colors]) unless ColorScheme.where(name: c[:name]).exists?
     end
 
     initializers.each do |callback|
-      callback.call
+      callback.call(self)
     end
   end
 
@@ -235,6 +262,10 @@ class Plugin::Instance
     end
   end
 
+  def enabled_site_setting(setting)
+    @enabled_site_setting = setting
+  end
+
   protected
 
   def register_assets!
diff --git a/spec/components/plugin/instance_spec.rb b/spec/components/plugin/instance_spec.rb
index 7388303d03f..961a0ba5dfc 100644
--- a/spec/components/plugin/instance_spec.rb
+++ b/spec/components/plugin/instance_spec.rb
@@ -23,6 +23,60 @@ describe Plugin::Instance do
     end
   end
 
+  context "enabling/disabling" do
+
+    it "is enabled by default" do
+      expect(Plugin::Instance.new.enabled?).to eq(true)
+    end
+
+    context "with a plugin that extends things" do
+
+      class Trout; end
+      class TroutSerializer < ApplicationSerializer; end
+
+      class TroutPlugin < Plugin::Instance
+        attr_accessor :enabled
+        def enabled?; @enabled; end
+      end
+
+      before do
+        @plugin = TroutPlugin.new
+        @trout = Trout.new
+
+        # New method
+        @plugin.add_to_class(:trout, :status?) { "evil" }
+
+        # DiscourseEvent
+        @hello_count = 0
+        @plugin.on(:hello) { @hello_count += 1 }
+
+        # Serializer
+        @plugin.add_to_serializer(:trout, :scales) { 1024 }
+        @serializer = TroutSerializer.new(@trout)
+      end
+
+      it "checks enabled/disabled functionality for extensions" do
+
+        # with an enabled plugin
+        @plugin.enabled = true
+        expect(@trout.status?).to eq("evil")
+        DiscourseEvent.trigger(:hello)
+        expect(@hello_count).to eq(1)
+        expect(@serializer.scales).to eq(1024)
+        expect(@serializer.include_scales?).to eq(true)
+
+        # When a plugin is disabled
+        @plugin.enabled = false
+        expect(@trout.status?).to eq(nil)
+        DiscourseEvent.trigger(:hello)
+        expect(@hello_count).to eq(1)
+        expect(@serializer.scales).to eq(1024)
+        expect(@serializer.include_scales?).to eq(false)
+
+      end
+    end
+  end
+
   context "register asset" do
     it "populates the DiscoursePluginRegistry" do
       plugin = Plugin::Instance.new nil, "/tmp/test.rb"