Remove root_guid from reshares when post is deleted

And cleanup old reshares with deleted root posts

closes #7578

Changelog.md

@@ -5,6 +5,7 @@
 * Remove Internet Explorer workarounds [#7557](https://github.com/diaspora/diaspora/pull/7557)
 * Sort notifications by last interaction [#7568](https://github.com/diaspora/diaspora/pull/7568)
 * Remove tiff support from photos [#7576](https://github.com/diaspora/diaspora/pull/7576)
+* Remove reference from reshares when original post is deleted [#7578](https://github.com/diaspora/diaspora/pull/7578)
 
 ## Bug fixes
 * Fix displaying polls with long answers [#7579](https://github.com/diaspora/diaspora/pull/7579)

app/models/post.rb

@@ -33,6 +33,10 @@ class Post < ApplicationRecord
     self.touch(:interacted_at)
   end
 
+  before_destroy do
+    reshares.update_all(root_guid: nil) # rubocop:disable Rails/SkipsModelValidations
+  end
+
   #scopes
   scope :includes_for_a_stream, -> {
     includes(:o_embed_cache,

db/migrate/20170824202628_cleanup_root_guids_from_reshares.rb

+class CleanupRootGuidsFromReshares < ActiveRecord::Migration[5.1]
+  def up
+    # rubocop:disable Rails/SkipsModelValidations
+    Reshare.joins("LEFT OUTER JOIN posts as root ON root.guid = posts.root_guid")
+           .where("root.id is NULL AND posts.root_guid is NOT NULL")
+           .update_all(root_guid: nil)
+    # rubocop:enable Rails/SkipsModelValidations
+  end
+end

spec/models/post_spec.rb

@@ -387,4 +387,13 @@ describe Post, :type => :model do
       expect(post.interacted_at).not_to be_blank
     end
   end
+
+  describe "#before_destroy" do
+    it "removes root_guid from reshares" do
+      post = FactoryGirl.create(:status_message, author: alice.person, public: true)
+      reshare = FactoryGirl.create(:reshare, author: bob.person, root: post)
+      post.destroy!
+      expect(reshare.reload.root_guid).to be_nil
+    end
+  end
 end