FIX: don't send email when the post was deleted

app/models/skipped_email_log.rb

@@ -31,7 +31,8 @@ class SkippedEmailLog < ActiveRecord::Base
       sender_message_blank: 16,
       sender_message_to_blank: 17,
       sender_text_part_body_blank: 18,
-      sender_body_blank: 19
+      sender_body_blank: 19,
+      sender_post_deleted: 20
     )
   end
 

lib/email/sender.rb

@@ -87,6 +87,10 @@ module Email
 
       if topic_id.present? && post_id.present?
         post = Post.find_by(id: post_id, topic_id: topic_id)
+
+        # guards against deleted posts
+        return skip(SkippedEmailLog.reason_types[:sender_post_deleted]) unless post
+
         topic = post.topic
         first_post = topic.ordered_posts.first
 
@@ -124,7 +128,7 @@ module Email
         end
 
         # https://www.ietf.org/rfc/rfc2919.txt
-        if topic && topic.category && !topic.category.uncategorized?
+        if topic&.category && !topic.category.uncategorized?
           list_id = "#{SiteSetting.title} | #{topic.category.name} <#{topic.category.name.downcase.tr(' ', '-')}.#{host}>"
 
           # subcategory case
@@ -199,7 +203,6 @@ module Email
         return skip(SkippedEmailLog.reason_types[:custom], custom_reason: e.message)
       end
 
-      # Save and return the email log
       email_log.save!
       email_log
     end

spec/components/email/sender_spec.rb

@@ -333,6 +333,25 @@ describe Email::Sender do
     end
   end
 
+  context 'with a deleted post' do
+
+    it 'should skip sending the email' do
+      post = Fabricate(:post, deleted_at: 1.day.ago)
+
+      message = Mail::Message.new to: 'disc@ourse.org', body: 'some content'
+      message.header['X-Discourse-Post-Id'] = post.id
+      message.header['X-Discourse-Topic-Id'] = post.topic_id
+      message.expects(:deliver_now).never
+
+      email_sender = Email::Sender.new(message, :valid_type)
+      expect { email_sender.send }.to change { SkippedEmailLog.count }
+
+      log = SkippedEmailLog.last
+      expect(log.reason_type).to eq(SkippedEmailLog.reason_types[:sender_post_deleted])
+    end
+
+  end
+
   context 'with a user' do
     let(:message) do
       message = Mail::Message.new to: 'eviltrout@test.domain', body: 'test body'