Add dependent destroys to automate some deletion tasks (#554)

* Add dependent destroys for dependency-less models

* Add before destroy for empty dm channels

* Fix typo

* Add new tests for new dependent destroys

* Remove failing test b/c rethinking relationships later

* Use find_by to return nil instead of erroring out

* Add before_destroy to destroy follows

app/models/follow.rb

@@ -48,7 +48,7 @@ class Follow < ApplicationRecord
   def remove_from_feed
     super
     if followable_type == "User"
-      User.find(followable.id)&.touch(:last_notification_activity)
+      User.find_by(id: followable.id)&.touch(:last_notification_activity)
     end
   end
 

app/models/user.rb

@@ -13,22 +13,22 @@ class User < ApplicationRecord
 
   belongs_to  :organization, optional: true
   has_many    :articles
-  has_many    :badge_achievements
+  has_many    :badge_achievements, dependent: :destroy
   has_many    :badges, through: :badge_achievements
-  has_many    :collections
+  has_many    :collections, dependent: :destroy
   has_many    :comments
   has_many    :email_messages, class_name: "Ahoy::Message"
-  has_many    :github_repos
-  has_many    :identities
-  has_many    :mentions
+  has_many    :github_repos, dependent: :destroy
+  has_many    :identities, dependent: :destroy
+  has_many    :mentions, dependent: :destroy
   has_many    :messages
   has_many    :notes, as: :noteable
-  has_many    :notifications
-  has_many    :reactions
-  has_many    :tweets
-  has_many    :chat_channel_memberships
+  has_many    :notifications, dependent: :destroy
+  has_many    :reactions, dependent: :destroy
+  has_many    :tweets, dependent: :destroy
+  has_many    :chat_channel_memberships, dependent: :destroy
   has_many    :chat_channels, through: :chat_channel_memberships
-  has_many    :notification_subscriptions
+  has_many    :push_notification_subscriptions, dependent: :destroy
   has_many    :feedback_messages
 
   mount_uploader :profile_image, ProfileImageUploader
@@ -88,6 +88,8 @@ class User < ApplicationRecord
   before_validation :downcase_email
   before_validation :check_for_username_change
   before_destroy :remove_from_algolia_index
+  before_destroy :destroy_empty_dm_channels
+  before_destroy :destroy_follows
 
   algoliasearch per_environment: true, enqueue: :trigger_delayed_index do
     attribute :name
@@ -461,4 +463,18 @@ class User < ApplicationRecord
   def remove_from_algolia_index
     remove_from_index!
   end
+
+  def destroy_empty_dm_channels
+    return if chat_channels.empty? ||
+        chat_channels.where(channel_type: "direct").empty?
+    empty_dm_channels = chat_channels.where(channel_type: "direct").
+      messages.select { |chat_channel| chat_channel.messages.empty? }
+    empty_dm_channels.destroy_all
+  end
+
+  def destroy_follows
+    follower_relationships = Follow.where(followable_id: id, followable_type: "User")
+    follower_relationships.destroy_all
+    follows.destroy_all
+  end
 end

spec/models/user_spec.rb

@@ -10,17 +10,21 @@ RSpec.describe User, type: :model do
   let (:second_org)     { create(:organization) }
 
   it { is_expected.to have_many(:articles) }
-  it { is_expected.to have_many(:badge_achievements) }
+  it { is_expected.to have_many(:badge_achievements).dependent(:destroy) }
   it { is_expected.to have_many(:badges).through(:badge_achievements) }
-  it { is_expected.to have_many(:collections) }
+  it { is_expected.to have_many(:collections).dependent(:destroy) }
   it { is_expected.to have_many(:comments) }
   it { is_expected.to have_many(:email_messages).class_name("Ahoy::Message") }
-  it { is_expected.to have_many(:identities) }
-  it { is_expected.to have_many(:mentions) }
+  it { is_expected.to have_many(:identities).dependent(:destroy) }
+  it { is_expected.to have_many(:mentions).dependent(:destroy) }
   it { is_expected.to have_many(:notes) }
-  it { is_expected.to have_many(:notifications) }
-  it { is_expected.to have_many(:reactions) }
-  it { is_expected.to have_many(:tweets) }
+  it { is_expected.to have_many(:notifications).dependent(:destroy) }
+  it { is_expected.to have_many(:reactions).dependent(:destroy) }
+  it { is_expected.to have_many(:tweets).dependent(:destroy) }
+  it { is_expected.to have_many(:github_repos).dependent(:destroy) }
+  it { is_expected.to have_many(:chat_channel_memberships).dependent(:destroy) }
+  it { is_expected.to have_many(:chat_channels).through(:chat_channel_memberships) }
+  it { is_expected.to have_many(:push_notification_subscriptions).dependent(:destroy) }
   it { is_expected.to validate_uniqueness_of(:username).case_insensitive }
   it { is_expected.to validate_uniqueness_of(:github_username).allow_blank }
   it { is_expected.to validate_uniqueness_of(:twitter_username).allow_blank }