FIX: `topic_destroyed` web hook couldn't find topic.

lib/topic_view.rb

@@ -37,15 +37,16 @@ class TopicView
     wpcf.flatten.uniq
   end
 
-  def initialize(topic_id, user = nil, options = {})
+  def initialize(topic_or_topic_id, user = nil, options = {})
-    @message_bus_last_id = MessageBus.last_id("/topic/#{topic_id}")
+    @topic = find_topic(topic_or_topic_id)
     @user = user
     @guardian = Guardian.new(@user)
-    @topic = find_topic(topic_id)
-    @print = options[:print].present?
 
     check_and_raise_exceptions
 
+    @message_bus_last_id = MessageBus.last_id("/topic/#{@topic.id}")
+    @print = options[:print].present?
+
     options.each do |key, value|
       self.instance_variable_set("@#{key}".to_sym, value)
     end
@@ -435,11 +436,15 @@ class TopicView
     @posts
   end
 
-  def find_topic(topic_id)
+  def find_topic(topic_or_topic_id)
+    if topic_or_topic_id.is_a?(Topic)
+      topic_or_topic_id
+    else
       # with_deleted covered in #check_and_raise_exceptions
-    finder = Topic.with_deleted.where(id: topic_id).includes(:category)
+      finder = Topic.with_deleted.where(id: topic_or_topic_id).includes(:category)
       finder.first
     end
+  end
 
   def unfiltered_posts
     result = filter_post_types(@topic.posts)

spec/components/topic_view_spec.rb

@@ -13,6 +13,11 @@ describe TopicView do
     expect { TopicView.new(1231232, evil_trout) }.to raise_error(Discourse::NotFound)
   end
 
+  it "accepts a topic or a topic id" do
+    expect(TopicView.new(topic, evil_trout).topic).to eq(topic)
+    expect(TopicView.new(topic.id, evil_trout).topic).to eq(topic)
+  end
+
   # see also spec/controllers/topics_controller_spec.rb TopicsController::show::permission errors
   it "raises an error if the user can't see the topic" do
     Guardian.any_instance.expects(:can_see?).with(topic).returns(false)