Add limit of 128 characters to users name

Truncate existing users names which exceed 128 characters
Include test for truncating users names

app/models/user.rb

@@ -159,7 +159,7 @@ class User < ApplicationRecord
   # Validations
   #
   # Note: devise :validatable above adds validations for :email and :password
-  validates :name, presence: true
+  validates :name, presence: true, length: { maximum: 128 }
   validates :email, confirmation: true
   validates :notification_email, presence: true
   validates :notification_email, devise_email: true, if: ->(user) { user.notification_email != user.email }

changelogs/unreleased/57493-add-limit-to-user-name.yml

@@ -0,0 +1,5 @@
+---
+title: Set user.name limit to 128 characters
+merge_request: 26146
+author:
+type: changed

db/migrate/20190325080727_truncate_user_fullname.rb

@@ -0,0 +1,21 @@
+# rubocop:disable Migration/UpdateLargeTable
+class TruncateUserFullname < ActiveRecord::Migration[5.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    truncated_name = Arel.sql('SUBSTRING(name from 1 for 128)')
+    where_clause = Arel.sql("LENGTH(name) > 128")
+
+    update_column_in_batches(:users, :name, truncated_name) do |table, query|
+      query.where(where_clause)
+    end
+  end
+
+  def down
+    # noop
+  end
+end

spec/migrations/truncate_user_fullname_spec.rb

@@ -0,0 +1,21 @@
+require 'spec_helper'
+require Rails.root.join('db', 'migrate', '20190325080727_truncate_user_fullname.rb')
+
+describe TruncateUserFullname, :migration do
+  let(:users) { table(:users) }
+
+  let(:user_short) { create_user(name: 'abc', email: 'test_short@example.com') }
+  let(:user_long) { create_user(name: 'a' * 200 + 'z', email: 'test_long@example.com') }
+
+  def create_user(params)
+    users.create!(params.merge(projects_limit: 0))
+  end
+
+  it 'truncates user full name to the first 128 characters' do
+    expect { migrate! }.to change { user_long.reload.name }.to('a' * 128)
+  end
+
+  it 'does not truncate short names' do
+    expect { migrate! }.not_to change { user_short.reload.name.length }
+  end
+end

spec/models/user_spec.rb

@@ -98,6 +98,11 @@ describe User do
   end
 
   describe 'validations' do
+    describe 'name' do
+      it { is_expected.to validate_presence_of(:name) }
+      it { is_expected.to validate_length_of(:name).is_at_most(128) }
+    end
+
     describe 'username' do
       it 'validates presence' do
         expect(subject).to validate_presence_of(:username)