Adds cop to enforce string limits on migrations

This cop will analyze migrations that add columns with string, and
report an offense if the string has no limit enforced

Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/64505

db/migrate/20171230123729_init_schema.rb

@@ -5,6 +5,7 @@
 # rubocop:disable Metrics/AbcSize
 # rubocop:disable Migration/AddConcurrentForeignKey
 # rubocop:disable Style/WordArray
+# rubocop:disable Migration/AddLimitToStringColumns
 
 class InitSchema < ActiveRecord::Migration[4.2]
   DOWNTIME = false
@@ -1852,3 +1853,4 @@ class InitSchema < ActiveRecord::Migration[4.2]
     raise ActiveRecord::IrreversibleMigration, "The initial migration is not revertable"
   end
 end
+# rubocop:enable Migration/AddLimitToStringColumns

db/migrate/20180101160629_create_prometheus_metrics.rb

@@ -4,6 +4,7 @@ class CreatePrometheusMetrics < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :prometheus_metrics do |t|
       t.references :project, index: true, foreign_key: { on_delete: :cascade }, null: false
       t.string :title, null: false
@@ -14,5 +15,6 @@ class CreatePrometheusMetrics < ActiveRecord::Migration[4.2]
       t.integer :group, null: false, index: true
       t.timestamps_with_timezone null: false
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180122162010_add_auto_devops_domain_to_application_settings.rb

@@ -8,6 +8,6 @@ class AddAutoDevopsDomainToApplicationSettings < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
-    add_column :application_settings, :auto_devops_domain, :string
+    add_column :application_settings, :auto_devops_domain, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180129193323_add_uploads_builder_context.rb

@@ -8,7 +8,9 @@ class AddUploadsBuilderContext < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     add_column :uploads, :mount_point, :string
     add_column :uploads, :secret, :string
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180212030105_add_external_ip_to_clusters_applications_ingress.rb

@@ -4,6 +4,6 @@ class AddExternalIpToClustersApplicationsIngress < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
-    add_column :clusters_applications_ingress, :external_ip, :string
+    add_column :clusters_applications_ingress, :external_ip, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180214093516_create_badges.rb

@@ -2,6 +2,7 @@ class CreateBadges < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :badges do |t|
       t.string     :link_url, null: false
       t.string     :image_url, null: false
@@ -11,6 +12,7 @@ class CreateBadges < ActiveRecord::Migration[4.2]
 
       t.timestamps_with_timezone null: false
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
 
     # rubocop:disable Migration/AddConcurrentForeignKey
     add_foreign_key :badges, :namespaces, column: :group_id, on_delete: :cascade

db/migrate/20180214155405_create_clusters_applications_runners.rb

@@ -13,7 +13,7 @@ class CreateClustersApplicationsRunners < ActiveRecord::Migration[4.2]
       t.index :cluster_id, unique: true
       t.integer :status, null: false
       t.timestamps_with_timezone null: false
-      t.string :version, null: false
+      t.string :version, null: false # rubocop:disable Migration/AddLimitToStringColumns
       t.text :status_reason
     end
 

db/migrate/20180216120000_add_pages_domain_verification.rb

@@ -3,6 +3,6 @@ class AddPagesDomainVerification < ActiveRecord::Migration[4.2]
 
   def change
     add_column :pages_domains, :verified_at, :datetime_with_timezone
-    add_column :pages_domains, :verification_code, :string
+    add_column :pages_domains, :verification_code, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180222043024_add_ip_address_to_runner.rb

@@ -4,6 +4,6 @@ class AddIpAddressToRunner < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
-    add_column :ci_runners, :ip_address, :string
+    add_column :ci_runners, :ip_address, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180308125206_add_user_internal_regex_to_application_setting.rb

@@ -4,7 +4,7 @@ class AddUserInternalRegexToApplicationSetting < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def up
-    add_column :application_settings, :user_default_internal_regex, :string, null: true
+    add_column :application_settings, :user_default_internal_regex, :string, null: true # rubocop:disable Migration/AddLimitToStringColumns
   end
 
   def down

db/migrate/20180315160435_add_external_auth_mutual_tls_fields_to_project_settings.rb

@@ -2,6 +2,7 @@ class AddExternalAuthMutualTlsFieldsToProjectSettings < ActiveRecord::Migration[
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     add_column :application_settings,
                :external_auth_client_cert, :text
     add_column :application_settings,
@@ -12,5 +13,6 @@ class AddExternalAuthMutualTlsFieldsToProjectSettings < ActiveRecord::Migration[
                :encrypted_external_auth_client_key_pass, :string
     add_column :application_settings,
                :encrypted_external_auth_client_key_pass_iv, :string
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180319190020_create_deploy_tokens.rb

@@ -2,6 +2,7 @@ class CreateDeployTokens < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :deploy_tokens do |t|
       t.boolean :revoked, default: false
       t.boolean :read_repository, null: false, default: false
@@ -15,5 +16,6 @@ class CreateDeployTokens < ActiveRecord::Migration[4.2]
 
       t.index [:token, :expires_at, :id], where: "(revoked IS FALSE)"
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180502122856_create_project_mirror_data.rb

@@ -3,6 +3,7 @@ class CreateProjectMirrorData < ActiveRecord::Migration[4.2]
 
   DOWNTIME = false
 
+  # rubocop:disable Migration/AddLimitToStringColumns
   def up
     if table_exists?(:project_mirror_data)
       add_column :project_mirror_data, :status, :string unless column_exists?(:project_mirror_data, :status)
@@ -17,6 +18,7 @@ class CreateProjectMirrorData < ActiveRecord::Migration[4.2]
       end
     end
   end
+  # rubocop:enable Migration/AddLimitToStringColumns
 
   def down
     remove_column :project_mirror_data, :status

db/migrate/20180503131624_create_remote_mirrors.rb

@@ -5,6 +5,7 @@ class CreateRemoteMirrors < ActiveRecord::Migration[4.2]
 
   disable_ddl_transaction!
 
+  # rubocop:disable Migration/AddLimitToStringColumns
   def up
     return if table_exists?(:remote_mirrors)
 
@@ -27,6 +28,7 @@ class CreateRemoteMirrors < ActiveRecord::Migration[4.2]
       t.timestamps null: false
     end
   end
+  # rubocop:enable Migration/AddLimitToStringColumns
 
   def down
     # ee/db/migrate/20160321161032_create_remote_mirrors_ee.rb will remove the table

db/migrate/20180503175053_ensure_missing_columns_to_project_mirror_data.rb

@@ -4,8 +4,8 @@ class EnsureMissingColumnsToProjectMirrorData < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def up
-    add_column :project_mirror_data, :status, :string unless column_exists?(:project_mirror_data, :status)
-    add_column :project_mirror_data, :jid, :string unless column_exists?(:project_mirror_data, :jid)
+    add_column :project_mirror_data, :status, :string unless column_exists?(:project_mirror_data, :status) # rubocop:disable Migration/AddLimitToStringColumns
+    add_column :project_mirror_data, :jid, :string unless column_exists?(:project_mirror_data, :jid) # rubocop:disable Migration/AddLimitToStringColumns
     add_column :project_mirror_data, :last_error, :text unless column_exists?(:project_mirror_data, :last_error)
   end
 

db/migrate/20180511131058_create_clusters_applications_jupyter.rb

@@ -7,17 +7,19 @@ class CreateClustersApplicationsJupyter < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :clusters_applications_jupyter do |t|
       t.references :cluster, null: false, unique: true, foreign_key: { on_delete: :cascade }
       t.references :oauth_application, foreign_key: { on_delete: :nullify }
 
       t.integer :status, null: false
-      t.string :version, null: false
-      t.string :hostname
+      t.string :version, null: false # rubocop:disable Migration/AddLimitToStringColumns
+      t.string :hostname # rubocop:disable Migration/AddLimitToStringColumns
 
       t.timestamps_with_timezone null: false
 
       t.text :status_reason
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180515121227_create_notes_diff_files.rb

@@ -4,6 +4,7 @@ class CreateNotesDiffFiles < ActiveRecord::Migration[4.2]
   disable_ddl_transaction!
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :note_diff_files do |t|
       t.references :diff_note, references: :notes, null: false, index: { unique: true }
       t.text :diff, null: false
@@ -18,5 +19,6 @@ class CreateNotesDiffFiles < ActiveRecord::Migration[4.2]
 
     # rubocop:disable Migration/AddConcurrentForeignKey
     add_foreign_key :note_diff_files, :notes, column: :diff_note_id, on_delete: :cascade
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180529093006_ensure_remote_mirror_columns.rb

@@ -8,7 +8,7 @@ class EnsureRemoteMirrorColumns < ActiveRecord::Migration[4.2]
   def up
     # rubocop:disable Migration/Datetime
     add_column :remote_mirrors, :last_update_started_at, :datetime unless column_exists?(:remote_mirrors, :last_update_started_at)
-    add_column :remote_mirrors, :remote_name, :string unless column_exists?(:remote_mirrors, :remote_name)
+    add_column :remote_mirrors, :remote_name, :string unless column_exists?(:remote_mirrors, :remote_name) # rubocop:disable Migration/AddLimitToStringColumns
 
     unless column_exists?(:remote_mirrors, :only_protected_branches)
       add_column_with_default(:remote_mirrors,

db/migrate/20180531185349_add_repository_languages.rb

@@ -4,6 +4,7 @@ class AddRepositoryLanguages < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def up
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table(:programming_languages) do |t|
       t.string :name, null: false
       t.string :color, null: false
@@ -19,6 +20,7 @@ class AddRepositoryLanguages < ActiveRecord::Migration[4.2]
     add_index :programming_languages, :name, unique: true
     add_index :repository_languages, [:project_id, :programming_language_id],
       unique: true, name: "index_repository_languages_on_project_and_languages_id"
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 
   def down

db/migrate/20180613081317_create_ci_builds_runner_session.rb

@@ -8,6 +8,7 @@ class CreateCiBuildsRunnerSession < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :ci_builds_runner_session, id: :bigserial do |t|
       t.integer :build_id, null: false
       t.string :url, null: false
@@ -17,5 +18,6 @@ class CreateCiBuildsRunnerSession < ActiveRecord::Migration[4.2]
       t.foreign_key :ci_builds, column: :build_id, on_delete: :cascade
       t.index :build_id, unique: true
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180713092803_create_user_statuses.rb

@@ -6,6 +6,7 @@ class CreateUserStatuses < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :user_statuses, id: false, primary_key: :user_id do |t|
       t.references :user,
                    foreign_key: { on_delete: :cascade },
@@ -16,5 +17,6 @@ class CreateUserStatuses < ActiveRecord::Migration[4.2]
       t.string :message, limit: 100
       t.string :message_html
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180814153625_add_commit_email_to_users.rb

@@ -28,6 +28,6 @@ class AddCommitEmailToUsers < ActiveRecord::Migration[4.2]
   # disable_ddl_transaction!
 
   def change
-    add_column :users, :commit_email, :string
+    add_column :users, :commit_email, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180831164908_add_identifier_to_prometheus_metric.rb

@@ -6,6 +6,6 @@ class AddIdentifierToPrometheusMetric < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
-    add_column :prometheus_metrics, :identifier, :string
+    add_column :prometheus_metrics, :identifier, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180910115836_add_attr_encrypted_columns_to_web_hook.rb

@@ -6,10 +6,12 @@ class AddAttrEncryptedColumnsToWebHook < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     add_column :web_hooks, :encrypted_token, :string
     add_column :web_hooks, :encrypted_token_iv, :string
 
     add_column :web_hooks, :encrypted_url, :string
     add_column :web_hooks, :encrypted_url_iv, :string
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20180910153412_add_token_digest_to_personal_access_tokens.rb

@@ -8,7 +8,7 @@ class AddTokenDigestToPersonalAccessTokens < ActiveRecord::Migration[4.2]
   def up
     change_column :personal_access_tokens, :token, :string, null: true
 
-    add_column :personal_access_tokens, :token_digest, :string
+    add_column :personal_access_tokens, :token_digest, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 
   def down

db/migrate/20180912111628_add_knative_application.rb

@@ -6,6 +6,7 @@ class AddKnativeApplication < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table "clusters_applications_knative" do |t|
       t.references :cluster, null: false, unique: true, foreign_key: { on_delete: :cascade }
 
@@ -16,5 +17,6 @@ class AddKnativeApplication < ActiveRecord::Migration[4.2]
       t.string "hostname"
       t.text "status_reason"
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181009190428_create_clusters_kubernetes_namespaces.rb

@@ -5,6 +5,7 @@ class CreateClustersKubernetesNamespaces < ActiveRecord::Migration[4.2]
   INDEX_NAME = 'kubernetes_namespaces_cluster_and_namespace'
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :clusters_kubernetes_namespaces, id: :bigserial do |t|
       t.references :cluster, null: false, index: true, foreign_key: { on_delete: :cascade }
       t.references :project, index: true, foreign_key: { on_delete: :nullify }
@@ -20,5 +21,6 @@ class CreateClustersKubernetesNamespaces < ActiveRecord::Migration[4.2]
 
       t.index [:cluster_id, :namespace], name: INDEX_NAME, unique: true
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181019032400_add_shards_table.rb

@@ -5,7 +5,7 @@ class AddShardsTable < ActiveRecord::Migration[4.2]
 
   def change
     create_table :shards do |t|
-      t.string :name, null: false, index: { unique: true }
+      t.string :name, null: false, index: { unique: true } # rubocop:disable Migration/AddLimitToStringColumns
     end
   end
 end

db/migrate/20181019032408_add_repositories_table.rb

@@ -6,7 +6,7 @@ class AddRepositoriesTable < ActiveRecord::Migration[4.2]
   def change
     create_table :repositories, id: :bigserial do |t|
       t.references :shard, null: false, index: true, foreign_key: { on_delete: :restrict }
-      t.string :disk_path, null: false, index: { unique: true }
+      t.string :disk_path, null: false, index: { unique: true } # rubocop:disable Migration/AddLimitToStringColumns
     end
 
     add_column :projects, :pool_repository_id, :bigint

db/migrate/20181025115728_add_private_commit_email_hostname_to_application_settings.rb

@@ -6,6 +6,6 @@ class AddPrivateCommitEmailHostnameToApplicationSettings < ActiveRecord::Migrati
   DOWNTIME = false
 
   def change
-    add_column(:application_settings, :commit_email_hostname, :string, null: true)
+    add_column(:application_settings, :commit_email_hostname, :string, null: true) # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181031190559_drop_gcp_clusters_table.rb

@@ -10,6 +10,7 @@ class DropGcpClustersTable < ActiveRecord::Migration[4.2]
   end
 
   def down
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :gcp_clusters do |t|
       # Order columns by best align scheme
       t.references :project, null: false, index: { unique: true }, foreign_key: { on_delete: :cascade }
@@ -49,5 +50,6 @@ class DropGcpClustersTable < ActiveRecord::Migration[4.2]
       t.text :encrypted_gcp_token
       t.string :encrypted_gcp_token_iv
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181101191341_create_clusters_applications_cert_manager.rb

@@ -6,6 +6,7 @@ class CreateClustersApplicationsCertManager < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :clusters_applications_cert_managers do |t|
       t.references :cluster, null: false, index: false, foreign_key: { on_delete: :cascade }
       t.integer :status, null: false
@@ -15,5 +16,6 @@ class CreateClustersApplicationsCertManager < ActiveRecord::Migration[4.2]
       t.text :status_reason
       t.index :cluster_id, unique: true
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181115140140_add_encrypted_runners_token_to_settings.rb

@@ -6,6 +6,6 @@ class AddEncryptedRunnersTokenToSettings < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
-    add_column :application_settings, :runners_registration_token_encrypted, :string
+    add_column :application_settings, :runners_registration_token_encrypted, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181116050532_knative_external_ip.rb

@@ -9,6 +9,6 @@ class KnativeExternalIp < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
-    add_column :clusters_applications_knative, :external_ip, :string
+    add_column :clusters_applications_knative, :external_ip, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181116141415_add_encrypted_runners_token_to_namespaces.rb

@@ -6,6 +6,6 @@ class AddEncryptedRunnersTokenToNamespaces < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
-    add_column :namespaces, :runners_token_encrypted, :string
+    add_column :namespaces, :runners_token_encrypted, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181116141504_add_encrypted_runners_token_to_projects.rb

@@ -6,6 +6,6 @@ class AddEncryptedRunnersTokenToProjects < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
-    add_column :projects, :runners_token_encrypted, :string
+    add_column :projects, :runners_token_encrypted, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181120151656_add_token_encrypted_to_ci_runners.rb

@@ -6,6 +6,6 @@ class AddTokenEncryptedToCiRunners < ActiveRecord::Migration[4.2]
   DOWNTIME = false
 
   def change
-    add_column :ci_runners, :token_encrypted, :string
+    add_column :ci_runners, :token_encrypted, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181122160027_create_project_repositories.rb

@@ -11,7 +11,7 @@ class CreateProjectRepositories < ActiveRecord::Migration[5.0]
   def change
     create_table :project_repositories, id: :bigserial do |t|
       t.references :shard, null: false, index: true, foreign_key: { on_delete: :restrict }
-      t.string :disk_path, null: false, index: { unique: true }
+      t.string :disk_path, null: false, index: { unique: true } # rubocop:disable Migration/AddLimitToStringColumns
       t.references :project, null: false, index: { unique: true }, foreign_key: { on_delete: :cascade }
     end
   end

db/migrate/20181123144235_create_suggestions.rb

@@ -8,7 +8,7 @@ class CreateSuggestions < ActiveRecord::Migration[5.0]
       t.references :note, foreign_key: { on_delete: :cascade }, null: false
       t.integer :relative_order, null: false, limit: 2
       t.boolean :applied, null: false, default: false
-      t.string :commit_id
+      t.string :commit_id # rubocop:disable Migration/AddLimitToStringColumns
       t.text :from_content, null: false
       t.text :to_content, null: false
 

db/migrate/20181128123704_add_state_to_pool_repository.rb

@@ -9,7 +9,7 @@ class AddStateToPoolRepository < ActiveRecord::Migration[5.0]
   # the transactions don't have to be disabled
   # rubocop: disable Migration/AddConcurrentForeignKey, Migration/AddIndex
   def change
-    add_column(:pool_repositories, :state, :string, null: true)
+    add_column(:pool_repositories, :state, :string, null: true) # rubocop:disable Migration/AddLimitToStringColumns
 
     add_column :pool_repositories, :source_project_id, :integer
     add_index :pool_repositories, :source_project_id, unique: true

db/migrate/20181129104854_add_token_encrypted_to_ci_builds.rb

@@ -6,6 +6,6 @@ class AddTokenEncryptedToCiBuilds < ActiveRecord::Migration[5.0]
   DOWNTIME = false
 
   def change
-    add_column :ci_builds, :token_encrypted, :string
+    add_column :ci_builds, :token_encrypted, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181203002526_add_project_bfg_object_map_column.rb

@@ -4,6 +4,6 @@ class AddProjectBfgObjectMapColumn < ActiveRecord::Migration[5.0]
   DOWNTIME = false
 
   def change
-    add_column :projects, :bfg_object_map, :string
+    add_column :projects, :bfg_object_map, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181211092510_add_name_author_id_and_sha_to_releases.rb

@@ -7,7 +7,7 @@ class AddNameAuthorIdAndShaToReleases < ActiveRecord::Migration[5.0]
 
   def change
     add_column :releases, :author_id, :integer
-    add_column :releases, :name, :string
-    add_column :releases, :sha, :string
+    add_column :releases, :name, :string # rubocop:disable Migration/AddLimitToStringColumns
+    add_column :releases, :sha, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181212171634_create_error_tracking_settings.rb

@@ -6,6 +6,7 @@ class CreateErrorTrackingSettings < ActiveRecord::Migration[5.0]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :project_error_tracking_settings, id: :int, primary_key: :project_id, default: nil do |t|
       t.boolean :enabled, null: false, default: true
       t.string :api_url, null: false
@@ -13,5 +14,6 @@ class CreateErrorTrackingSettings < ActiveRecord::Migration[5.0]
       t.string :encrypted_token_iv
       t.foreign_key :projects, column: :project_id, on_delete: :cascade
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20181228175414_create_releases_link_table.rb

@@ -6,6 +6,7 @@ class CreateReleasesLinkTable < ActiveRecord::Migration[5.0]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :release_links, id: :bigserial do |t|
       t.references :release, null: false, index: false, foreign_key: { on_delete: :cascade }
       t.string :url, null: false
@@ -15,5 +16,6 @@ class CreateReleasesLinkTable < ActiveRecord::Migration[5.0]
       t.index [:release_id, :url], unique: true
       t.index [:release_id, :name], unique: true
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20190109153125_add_merge_request_external_diffs.rb

@@ -11,7 +11,7 @@ class AddMergeRequestExternalDiffs < ActiveRecord::Migration[5.0]
 
   def change
     # Allow the merge request diff to store details about an external file
-    add_column :merge_request_diffs, :external_diff, :string
+    add_column :merge_request_diffs, :external_diff, :string # rubocop:disable Migration/AddLimitToStringColumns
     add_column :merge_request_diffs, :external_diff_store, :integer
     add_column :merge_request_diffs, :stored_externally, :boolean
 

db/migrate/20190114172110_add_domain_to_cluster.rb

@@ -4,6 +4,6 @@ class AddDomainToCluster < ActiveRecord::Migration[5.0]
   DOWNTIME = false
 
   def change
-    add_column :clusters, :domain, :string
+    add_column :clusters, :domain, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20190115092821_add_columns_project_error_tracking_settings.rb

@@ -6,8 +6,8 @@ class AddColumnsProjectErrorTrackingSettings < ActiveRecord::Migration[5.0]
   DOWNTIME = false
 
   def change
-    add_column :project_error_tracking_settings, :project_name, :string
-    add_column :project_error_tracking_settings, :organization_name, :string
+    add_column :project_error_tracking_settings, :project_name, :string # rubocop:disable Migration/AddLimitToStringColumns
+    add_column :project_error_tracking_settings, :organization_name, :string # rubocop:disable Migration/AddLimitToStringColumns
 
     change_column_default :project_error_tracking_settings, :enabled, from: true, to: false
 

db/migrate/20190116234221_add_sorting_fields_to_user_preference.rb

@@ -10,8 +10,8 @@ class AddSortingFieldsToUserPreference < ActiveRecord::Migration[5.0]
   DOWNTIME = false
 
   def up
-    add_column :user_preferences, :issues_sort, :string
-    add_column :user_preferences, :merge_requests_sort, :string
+    add_column :user_preferences, :issues_sort, :string # rubocop:disable Migration/AddLimitToStringColumns
+    add_column :user_preferences, :merge_requests_sort, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 
   def down

db/migrate/20190301182457_add_external_hostname_to_ingress_and_knative.rb

@@ -4,7 +4,7 @@ class AddExternalHostnameToIngressAndKnative < ActiveRecord::Migration[5.0]
   DOWNTIME = false
 
   def change
-    add_column :clusters_applications_ingress, :external_hostname, :string
-    add_column :clusters_applications_knative, :external_hostname, :string
+    add_column :clusters_applications_ingress, :external_hostname, :string # rubocop:disable Migration/AddLimitToStringColumns
+    add_column :clusters_applications_knative, :external_hostname, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20190320174702_add_lets_encrypt_notification_email_to_application_settings.rb

@@ -10,6 +10,6 @@ class AddLetsEncryptNotificationEmailToApplicationSettings < ActiveRecord::Migra
   DOWNTIME = false
 
   def change
-    add_column :application_settings, :lets_encrypt_notification_email, :string
+    add_column :application_settings, :lets_encrypt_notification_email, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20190325105715_add_fields_to_user_preferences.rb

@@ -11,7 +11,7 @@ class AddFieldsToUserPreferences < ActiveRecord::Migration[5.0]
   DOWNTIME = false
 
   def up
-    add_column(:user_preferences, :timezone, :string)
+    add_column(:user_preferences, :timezone, :string) # rubocop:disable Migration/AddLimitToStringColumns
     add_column(:user_preferences, :time_display_relative, :boolean)
     add_column(:user_preferences, :time_format_in_24h, :boolean)
   end

db/migrate/20190327163904_add_notification_email_to_notification_settings.rb

@@ -6,6 +6,6 @@ class AddNotificationEmailToNotificationSettings < ActiveRecord::Migration[5.0]
   DOWNTIME = false
 
   def change
-    add_column :notification_settings, :notification_email, :string
+    add_column :notification_settings, :notification_email, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20190402150158_backport_enterprise_schema.rb

@@ -2,6 +2,7 @@
 
 # rubocop: disable Metrics/AbcSize
 # rubocop: disable Migration/Datetime
+# rubocop: disable Migration/AddLimitToStringColumns
 class BackportEnterpriseSchema < ActiveRecord::Migration[5.0]
   include Gitlab::Database::MigrationHelpers
 
@@ -2190,3 +2191,4 @@ class BackportEnterpriseSchema < ActiveRecord::Migration[5.0]
 end
 # rubocop: enable Metrics/AbcSize
 # rubocop: enable Migration/Datetime
+# rubocop: enable Migration/AddLimitToStringColumns

db/migrate/20190409224933_add_name_to_geo_nodes.rb

@@ -10,7 +10,7 @@ class AddNameToGeoNodes < ActiveRecord::Migration[5.0]
   DOWNTIME = false
 
   def up
-    add_column :geo_nodes, :name, :string
+    add_column :geo_nodes, :name, :string # rubocop:disable Migration/AddLimitToStringColumns
 
     # url is also unique, and its type and size is identical to the name column,
     # so this is safe.

db/migrate/20190422082247_create_project_metrics_settings.rb

@@ -7,7 +7,7 @@ class CreateProjectMetricsSettings < ActiveRecord::Migration[5.0]
 
   def change
     create_table :project_metrics_settings, id: :int, primary_key: :project_id, default: nil do |t|
-      t.string :external_dashboard_url, null: false
+      t.string :external_dashboard_url, null: false # rubocop:disable Migration/AddLimitToStringColumns
       t.foreign_key :projects, column: :project_id, on_delete: :cascade
     end
   end

db/migrate/20190429082448_create_pages_domain_acme_orders.rb

@@ -10,6 +10,7 @@ class CreatePagesDomainAcmeOrders < ActiveRecord::Migration[5.1]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :pages_domain_acme_orders do |t|
       t.references :pages_domain, null: false, index: true, foreign_key: { on_delete: :cascade }, type: :integer
 
@@ -24,5 +25,6 @@ class CreatePagesDomainAcmeOrders < ActiveRecord::Migration[5.1]
       t.text :encrypted_private_key, null: false
       t.text :encrypted_private_key_iv, null: false
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20190430131225_create_issue_tracker_data.rb

@@ -9,6 +9,7 @@ class CreateIssueTrackerData < ActiveRecord::Migration[5.1]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :issue_tracker_data do |t|
       t.references :service, foreign_key: { on_delete: :cascade }, type: :integer, index: true, null: false
       t.timestamps_with_timezone
@@ -19,5 +20,6 @@ class CreateIssueTrackerData < ActiveRecord::Migration[5.1]
       t.string :encrypted_new_issue_url
       t.string :encrypted_new_issue_url_iv
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20190430142025_create_jira_tracker_data.rb

@@ -9,6 +9,7 @@ class CreateJiraTrackerData < ActiveRecord::Migration[5.1]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :jira_tracker_data do |t|
       t.references :service, foreign_key: { on_delete: :cascade }, type: :integer, index: true, null: false
       t.timestamps_with_timezone
@@ -22,5 +23,6 @@ class CreateJiraTrackerData < ActiveRecord::Migration[5.1]
       t.string :encrypted_password_iv
       t.string :jira_issue_transition_id
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20190514105711_create_ip_restriction.rb

@@ -12,7 +12,7 @@ class CreateIpRestriction < ActiveRecord::Migration[5.1]
                    type: :integer,
                    null: false,
                    index: true
-      t.string :range, null: false
+      t.string :range, null: false # rubocop:disable Migration/AddLimitToStringColumns
     end
 
     add_foreign_key(:ip_restrictions, :namespaces, column: :group_id, on_delete: :cascade) # rubocop: disable Migration/AddConcurrentForeignKey

db/migrate/20190527011309_add_required_template_name_to_application_settings.rb

@@ -10,6 +10,6 @@ class AddRequiredTemplateNameToApplicationSettings < ActiveRecord::Migration[5.1
   DOWNTIME = false
 
   def change
-    add_column :application_settings, :required_instance_ci_template, :string, null: true
+    add_column :application_settings, :required_instance_ci_template, :string, null: true # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20190606054742_add_token_encrypted_to_operations_feature_flags_clients.rb

@@ -6,6 +6,6 @@ class AddTokenEncryptedToOperationsFeatureFlagsClients < ActiveRecord::Migration
   DOWNTIME = false
 
   def change
-    add_column :operations_feature_flags_clients, :token_encrypted, :string
+    add_column :operations_feature_flags_clients, :token_encrypted, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20190613044655_add_username_to_deploy_tokens.rb

@@ -4,6 +4,6 @@ class AddUsernameToDeployTokens < ActiveRecord::Migration[5.1]
   DOWNTIME = false
 
   def change
-    add_column :deploy_tokens, :username, :string
+    add_column :deploy_tokens, :username, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20190613073003_create_project_aliases.rb

@@ -8,7 +8,7 @@ class CreateProjectAliases < ActiveRecord::Migration[5.1]
   def change
     create_table :project_aliases do |t|
       t.references :project, null: false, index: true, foreign_key: { on_delete: :cascade }, type: :integer
-      t.string :name, null: false, index: { unique: true }
+      t.string :name, null: false, index: { unique: true } # rubocop:disable Migration/AddLimitToStringColumns
 
       t.timestamps_with_timezone null: false
     end

db/migrate/20190621151636_add_merge_request_rebase_jid.rb

@@ -4,6 +4,6 @@ class AddMergeRequestRebaseJid < ActiveRecord::Migration[5.1]
   DOWNTIME = false
 
   def change
-    add_column :merge_requests, :rebase_jid, :string
+    add_column :merge_requests, :rebase_jid, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/migrate/20190624123615_add_grafana_url_to_settings.rb

@@ -8,8 +8,10 @@ class AddGrafanaUrlToSettings < ActiveRecord::Migration[5.1]
   DOWNTIME = false
 
   def up
+    # rubocop:disable Migration/AddLimitToStringColumns
     add_column_with_default(:application_settings, :grafana_url, :string,
                             default: '/-/grafana', allow_null: false)
+    # rubocop:enable Migration/AddLimitToStringColumns
   end
 
   def down

db/migrate/20190711124721_create_job_variables.rb

@@ -10,6 +10,7 @@ class CreateJobVariables < ActiveRecord::Migration[5.1]
   DOWNTIME = false
 
   def change
+    # rubocop:disable Migration/AddLimitToStringColumns
     create_table :ci_job_variables do |t|
       t.string :key, null: false
       t.text :encrypted_value
@@ -17,6 +18,7 @@ class CreateJobVariables < ActiveRecord::Migration[5.1]
       t.references :job, null: false, index: true, foreign_key: { to_table: :ci_builds, on_delete: :cascade }
       t.integer :variable_type, null: false, limit: 2, default: 1
     end
+    # rubocop:enable Migration/AddLimitToStringColumns
 
     add_index :ci_job_variables, [:key, :job_id], unique: true
   end

db/post_migrate/20181013005024_remove_koding_from_application_settings.rb

@@ -12,6 +12,6 @@ class RemoveKodingFromApplicationSettings < ActiveRecord::Migration[4.2]
 
   def down
     add_column :application_settings, :koding_enabled, :boolean # rubocop:disable Migration/SaferBooleanColumn
-    add_column :application_settings, :koding_url, :string
+    add_column :application_settings, :koding_url, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/post_migrate/20190404231137_remove_alternate_url_from_geo_nodes.rb

@@ -16,6 +16,6 @@ class RemoveAlternateUrlFromGeoNodes < ActiveRecord::Migration[5.0]
   end
 
   def down
-    add_column :geo_nodes, :alternate_url, :string
+    add_column :geo_nodes, :alternate_url, :string # rubocop:disable Migration/AddLimitToStringColumns
   end
 end

db/post_migrate/20190625184066_remove_sentry_from_application_settings.rb

@@ -32,7 +32,7 @@ class RemoveSentryFromApplicationSettings < ActiveRecord::Migration[5.0]
     end
 
     SENTRY_DSN_COLUMNS.each do |column|
-      add_column(:application_settings, column, :string) unless column_exists?(:application_settings, column)
+      add_column(:application_settings, column, :string) unless column_exists?(:application_settings, column) # rubocop:disable Migration/AddLimitToStringColumns
     end
   end
 end

rubocop/cop/migration/add_limit_to_string_columns.rb

+# frozen_string_literal: true
+
+require_relative '../../migration_helpers'
+
+module RuboCop
+  module Cop
+    module Migration
+      # Cop that enforces length constraints to string columns
+      class AddLimitToStringColumns < RuboCop::Cop::Cop
+        include MigrationHelpers
+
+        ADD_COLUMNS_METHODS = %i(add_column add_column_with_default).freeze
+
+        MSG = 'String columns should have a limit constraint. 255 is suggested'.freeze
+
+        def on_def(node)
+          return unless in_migration?(node)
+
+          node.each_descendant(:send) do |send_node|
+            next unless string_operation?(send_node)
+
+            add_offense(send_node, location: :selector) unless limit_on_string_column?(send_node)
+          end
+        end
+
+        private
+
+        def string_operation?(node)
+          modifier = node.children[0]
+          migration_method = node.children[1]
+
+          if migration_method == :string
+            modifier.type == :lvar
+          elsif ADD_COLUMNS_METHODS.include?(migration_method)
+            modifier.nil? && string_column?(node.children[4])
+          end
+        end
+
+        def string_column?(column_type)
+          column_type.type == :sym && column_type.value == :string
+        end
+
+        def limit_on_string_column?(node)
+          migration_method = node.children[1]
+
+          if migration_method == :string
+            limit_present?(node.children)
+          elsif ADD_COLUMNS_METHODS.include?(migration_method)
+            limit_present?(node)
+          end
+        end
+
+        def limit_present?(statement)
+          !(statement.to_s =~ /:limit/).nil?
+        end
+      end
+    end
+  end
+end

rubocop/rubocop.rb

@@ -17,6 +17,7 @@ require_relative 'cop/migration/add_column'
 require_relative 'cop/migration/add_concurrent_foreign_key'
 require_relative 'cop/migration/add_concurrent_index'
 require_relative 'cop/migration/add_index'
+require_relative 'cop/migration/add_limit_to_string_columns'
 require_relative 'cop/migration/add_reference'
 require_relative 'cop/migration/add_timestamps'
 require_relative 'cop/migration/datetime'

spec/rubocop/cop/migration/add_limit_to_string_columns_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+
+require_relative '../../../../rubocop/cop/migration/add_limit_to_string_columns'
+
+describe RuboCop::Cop::Migration::AddLimitToStringColumns do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  context 'in migration' do
+    before do
+      allow(cop).to receive(:in_migration?).and_return(true)
+
+      inspect_source(migration)
+    end
+
+    context 'when creating a table' do
+      context 'with string columns and limit' do
+        let(:migration) do
+          %q(
+           class CreateUsers < ActiveRecord::Migration[5.2]
+             DOWNTIME = false
+
+             def change
+               create_table :users do |t|
+                 t.string :username, null: false, limit: 255
+                 t.timestamps_with_timezone null: true
+               end
+             end
+           end
+          )
+        end
+
+        it 'register no offense' do
+          expect(cop.offenses.size).to eq(0)
+        end
+
+        context 'with limit in a different position' do
+          let(:migration) do
+            %q(
+             class CreateUsers < ActiveRecord::Migration[5.2]
+               DOWNTIME = false
+
+               def change
+                 create_table :users do |t|
+                   t.string :username, limit: 255, null: false
+                   t.timestamps_with_timezone null: true
+                 end
+               end
+             end
+            )
+          end
+
+          it 'registers an offense' do
+            expect(cop.offenses.size).to eq(0)
+          end
+        end
+      end
+
+      context 'with string columns and no limit' do
+        let(:migration) do
+          %q(
+           class CreateUsers < ActiveRecord::Migration[5.2]
+             DOWNTIME = false
+
+             def change
+               create_table :users do |t|
+                 t.string :username, null: false
+                 t.timestamps_with_timezone null: true
+               end
+             end
+           end
+          )
+        end
+
+        it 'registers an offense' do
+          expect(cop.offenses.size).to eq(1)
+          expect(cop.offenses.first.message)
+            .to eq('String columns should have a limit constraint. 255 is suggested')
+        end
+      end
+
+      context 'with no string columns' do
+        let(:migration) do
+          %q(
+            class CreateMilestoneReleases < ActiveRecord::Migration[5.2]
+              DOWNTIME = false
+
+              def change
+                create_table :milestone_releases do |t|
+                  t.integer :milestone_id
+                  t.integer :release_id
+                end
+              end
+            end
+          )
+        end
+
+        it 'register no offense' do
+          expect(cop.offenses.size).to eq(0)
+        end
+      end
+    end
+
+    context 'when adding columns' do
+      context 'with string columns with limit' do
+        let(:migration) do
+          %q(
+            class AddEmailToUsers < ActiveRecord::Migration[5.2]
+              DOWNTIME = false
+
+              def change
+                add_column :users, :email, :string, limit: 255
+              end
+            end
+          )
+        end
+
+        it 'registers no offense' do
+          expect(cop.offenses.size).to eq(0)
+        end
+
+        context 'with limit in a different position' do
+          let(:migration) do
+            %q(
+              class AddEmailToUsers < ActiveRecord::Migration[5.2]
+                DOWNTIME = false
+
+                def change
+                  add_column :users, :email, :string, limit: 255, default: 'example@email.com'
+                end
+              end
+            )
+          end
+
+          it 'registers no offense' do
+            expect(cop.offenses.size).to eq(0)
+          end
+        end
+      end
+
+      context 'with string columns with no limit' do
+        let(:migration) do
+          %q(
+            class AddEmailToUsers < ActiveRecord::Migration[5.2]
+              DOWNTIME = false
+
+              def change
+                add_column :users, :email, :string
+              end
+            end
+          )
+        end
+
+        it 'registers offense' do
+          expect(cop.offenses.size).to eq(1)
+          expect(cop.offenses.first.message)
+            .to eq('String columns should have a limit constraint. 255 is suggested')
+        end
+      end
+
+      context 'with no string columns' do
+        let(:migration) do
+          %q(
+            class AddEmailToUsers < ActiveRecord::Migration[5.2]
+              DOWNTIME = false
+
+              def change
+                add_column :users, :active, :boolean, default: false
+              end
+            end
+          )
+        end
+
+        it 'registers no offense' do
+          expect(cop.offenses.size).to eq(0)
+        end
+      end
+    end
+
+    context 'with add_column_with_default' do
+      context 'with a limit' do
+        let(:migration) do
+          %q(
+           class AddRuleTypeToApprovalMergeRequestRules < ActiveRecord::Migration[5.2]
+             DOWNTIME = false
+
+             def change
+               add_column_with_default(:approval_merge_request_rules, :rule_type, :string, limit: 2, default: 1)
+             end
+           end
+           )
+        end
+
+        it 'registers no offense' do
+          expect(cop.offenses.size).to eq(0)
+        end
+      end
+
+      context 'without a limit' do
+        let(:migration) do
+          %q(
+           class AddRuleTypeToApprovalMergeRequestRules < ActiveRecord::Migration[5.2]
+             DOWNTIME = false
+
+             def change
+               add_column_with_default(:approval_merge_request_rules, :rule_type, :string, default: 1)
+             end
+           end
+           )
+        end
+
+        it 'registers an offense' do
+          expect(cop.offenses.size).to eq(1)
+        end
+      end
+    end
+
+    context 'with methods' do
+      let(:migration) do
+        %q(
+          class AddEmailToUsers < ActiveRecord::Migration[5.2]
+            DOWNTIME = false
+
+            def change
+              add_column_if_table_not_exists :users, :first_name, :string, limit: 255
+              search_namespace(user_name)
+            end
+
+            def add_column_if_not_exists(table, name, *args)
+              add_column(table, name, *args) unless column_exists?(table, name)
+            end
+
+            def search_namespace(username)
+               Uniquify.new.string(username) do |str|
+                query = "SELECT id FROM namespaces WHERE parent_id IS NULL AND path='#{str}' LIMIT 1"
+                connection.exec_query(query)
+              end
+            end
+          end
+        )
+      end
+
+      it 'registers no offense' do
+        expect(cop.offenses.size).to eq(0)
+      end
+    end
+  end
+
+  context 'outside of migrations' do
+    let(:active_record_model) do
+      %q(
+      class User < ApplicationRecord
+      end
+      )
+    end
+
+    it 'registers no offense' do
+      inspect_source(active_record_model)
+
+      expect(cop.offenses.size).to eq(0)
+    end
+  end
+end