FEATURE: match user title when primary group changes

When primary group changes and the user's title is the previous primary
group's title, change the title to the new primary group's title

app/models/user.rb

@@ -108,6 +108,7 @@ class User < ActiveRecord::Base
 
   before_save :update_username_lower
   before_save :ensure_password_is_hashed
+  before_save :match_title_to_primary_group_changes
 
   after_save :expire_tokens_if_password_changed
   after_save :clear_global_notice_if_needed
@@ -1273,6 +1274,14 @@ class User < ActiveRecord::Base
     end
   end
 
+  def match_title_to_primary_group_changes
+    return unless primary_group_id_changed?
+
+    if title == Group.where(id: primary_group_id_was).pluck(:title).first
+      self.title = primary_group&.title
+    end
+  end
+
   private
 
   def previous_visit_at_update_required?(timestamp)

spec/models/user_spec.rb

@@ -1814,4 +1814,16 @@ describe User do
 
   end
 
+  describe '#match_title_to_primary_group_changes' do
+    let(:primary_group_a) { Fabricate(:group, title: 'A', users: [user]) }
+    let(:primary_group_b) { Fabricate(:group, title: 'B', users: [user]) }
+
+    it "updates user's title only when it is blank or matches the previous primary group" do
+      expect { user.update(primary_group: primary_group_a) }.to change { user.reload.title }.from(nil).to('A')
+      expect { user.update(primary_group: primary_group_b) }.to change { user.reload.title }.from('A').to('B')
+
+      user.update(title: 'Different')
+      expect { user.update(primary_group: primary_group_a) }.to_not change { user.reload.title }
+    end
+  end
 end

spec/requests/admin/users_controller_spec.rb

@@ -381,6 +381,7 @@ RSpec.describe Admin::UsersController do
   describe '#primary_group' do
     let(:group) { Fabricate(:group) }
     let(:another_user) { Fabricate(:coding_horror) }
+    let(:another_group) { Fabricate(:group, title: 'New') }
 
     it "raises an error when the user doesn't have permission" do
       sign_in(user)
@@ -427,6 +428,41 @@ RSpec.describe Admin::UsersController do
       another_user.reload
       expect(another_user.primary_group_id).to eq(nil)
     end
+
+    it "updates user's title when it matches the previous primary group title" do
+      group.update_columns(primary_group: true, title: 'Previous')
+      group.add(another_user)
+      another_group.add(another_user)
+
+      expect(another_user.reload.title).to eq('Previous')
+
+      put "/admin/users/#{another_user.id}/primary_group.json", params: {
+        primary_group_id: another_group.id
+      }
+
+      another_user.reload
+      expect(response.status).to eq(200)
+      expect(another_user.primary_group_id).to eq(another_group.id)
+      expect(another_user.title).to eq('New')
+    end
+
+    it "doesn't update user's title when it does not match the previous primary group title" do
+      another_user.update_columns(title: 'Different')
+      group.update_columns(primary_group: true, title: 'Previous')
+      another_group.add(another_user)
+      group.add(another_user)
+
+      expect(another_user.reload.title).to eq('Different')
+
+      put "/admin/users/#{another_user.id}/primary_group.json", params: {
+        primary_group_id: another_group.id
+      }
+
+      another_user.reload
+      expect(response.status).to eq(200)
+      expect(another_user.primary_group_id).to eq(another_group.id)
+      expect(another_user.title).to eq('Different')
+    end
   end
 
   describe '#destroy' do