2 files changed, 44 insertions, 0 deletions
diff --git a/app/models/account.rb b/app/models/account.rb
index bc9bcc72d..f794d8a29 100644
--- a/app/models/account.rb
+++ b/app/models/account.rb
@@ -67,6 +67,7 @@ class Account < ApplicationRecord
   include Paginable
   include AccountCounters
   include DomainNormalizable
+  include AccountMerging
 
   TRUST_LEVELS = {
     untrusted: 0,
diff --git a/app/models/concerns/account_merging.rb b/app/models/concerns/account_merging.rb
new file mode 100644
index 000000000..691d02e03
--- /dev/null
+++ b/app/models/concerns/account_merging.rb
@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+module AccountMerging
+  extend ActiveSupport::Concern
+
+  def merge_with!(other_account)
+    # Since it's the same remote resource, the remote resource likely
+    # already believes we are following/blocking, so it's safe to
+    # re-attribute the relationships too. However, during the presence
+    # of the index bug users could have *also* followed the reference
+    # account already, therefore mass update will not work and we need
+    # to check for (and skip past) uniqueness errors
+
+    owned_classes = [
+      Status, StatusPin, MediaAttachment, Poll, Report, Tombstone, Favourite,
+      Follow, FollowRequest, Block, Mute, AccountIdentityProof,
+      AccountModerationNote, AccountPin, AccountStat, ListAccount,
+      PollVote, Mention
+    ]
+
+    owned_classes.each do |klass|
+      klass.where(account_id: other_account.id).find_each do |record|
+        begin
+          record.update_attribute(:account_id, id)
+        rescue ActiveRecord::RecordNotUnique
+          next
+        end
+      end
+    end
+
+    target_classes = [Follow, FollowRequest, Block, Mute, AccountModerationNote, AccountPin]
+
+    target_classes.each do |klass|
+      klass.where(target_account_id: other_account.id).find_each do |record|
+        begin
+          record.update_attribute(:target_account_id, id)
+        rescue ActiveRecord::RecordNotUnique
+          next
+        end
+      end
+    end
+  end
+end