FEATURE: Merge user associated accounts, favouring the target user upon conflict (#26645)

app/services/user_merger.rb

@@ -18,6 +18,7 @@ class UserMerger
     merge_user_visits
     update_site_settings
     merge_user_attributes
+    merge_user_associated_accounts
 
     DiscourseEvent.trigger(:merging_users, @source_user, @target_user)
     update_user_stats
@@ -294,6 +295,29 @@ class UserMerger
     SQL
   end
 
+  def merge_user_associated_accounts
+    if @acting_user
+      ::MessageBus.publish "/merge_user",
+                           {
+                             message:
+                               I18n.t("admin.user.merge_user.merging_user_associated_accounts"),
+                           },
+                           user_ids: [@acting_user.id]
+    end
+
+    UserAssociatedAccount.where(user_id: @source_user.id).update_all(<<~SQL)
+      user_id = CASE
+        WHEN EXISTS (
+          SELECT 1
+          FROM user_associated_accounts AS conflicts
+          WHERE (conflicts.user_id = #{@target_user.id} AND conflicts.provider_name = user_associated_accounts.provider_name)
+        )
+        THEN NULL
+        ELSE #{@target_user.id}
+      END
+    SQL
+  end
+
   def update_user_ids
     if @acting_user
       ::MessageBus.publish "/merge_user",

config/locales/server.en.yml

@@ -2931,6 +2931,7 @@ en:
         updating_site_settings: "Updating site settings…"
         updating_user_stats: "Updating user stats…"
         merging_user_attributes: "Merging user attributes…"
+        merging_user_associated_accounts: "Merging user associated accounts…"
         updating_user_ids: "Updating user ids…"
         deleting_source_user: "Deleting source user…"
   user:

spec/fabricators/user_associated_account_fabricator.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+Fabricator(:user_associated_account) do
+  provider_name "meecrosof"
+  provider_uid { sequence(:key) { |i| "#{i + 1}" } }
+  user
+  info { |attrs| { name: attrs[:user].username, email: attrs[:user].email } }
+end

spec/services/user_merger_spec.rb

@@ -1084,6 +1084,44 @@ RSpec.describe UserMerger do
     end
   end
 
+  context "with user associated accounts (UAAs)" do
+    context "when only merging account has UAAs" do
+      it "transfers the source user UAA to the target" do
+        source_uaa = Fabricate(:user_associated_account, user: source_user)
+
+        merge_users!
+
+        expect(source_uaa.reload.user).to eq(target_user)
+      end
+    end
+
+    context "when both accounts have UAAs" do
+      context "when both accounts' UAAs have different provider_names" do
+        it "transfers the source user UAA to the target and keeps both" do
+          source_uaa = Fabricate(:user_associated_account, user: source_user, provider_name: "x")
+          target_uaa = Fabricate(:user_associated_account, user: target_user, provider_name: "y")
+
+          merge_users!
+
+          expect(target_uaa.reload.user).to eq(target_user)
+          expect(source_uaa.reload.user).to eq(target_user)
+        end
+      end
+
+      context "when both accounts' UAAs have same provider_names" do
+        it "keeps only the target UAA" do
+          source_uaa = Fabricate(:user_associated_account, user: source_user, provider_name: "x")
+          target_uaa = Fabricate(:user_associated_account, user: target_user, provider_name: "x")
+
+          merge_users!
+
+          expect(target_uaa.reload.user).to eq(target_user)
+          expect(source_uaa.reload.user).to eq(nil)
+        end
+      end
+    end
+  end
+
   it "updates users" do
     walter.update!(approved_by: source_user)
     upload = Fabricate(:upload)