Summarised data: Breaking changes on Rails 6
actioncable
https://github.com/rails/rails/blob/v6.0.0.rc1/actioncable/CHANGELOG.md
npm package renamed from actioncable to @rails/actioncable.
Configuration of the WebSocket adapter and logger adapter have been moved from properties of ActionCable to properties of ActionCable.adapters.
The ActionCable.startDebugging() and ActionCable.stopDebugging() methods have been removed and replaced with the property ActionCable.logger.enabled.
actionmailbox
https://github.com/rails/rails/blob/v6.0.0.rc1/actionmailbox/CHANGELOG.md
- (new module introduced from 6.0.0)
actionmailer
https://github.com/rails/rails/blob/v6.0.0.rc1/actionmailer/CHANGELOG.md
Deprecate ActionMailer::Base.receive in favor of actionmailbox.
actionpack
https://github.com/rails/rails/blob/v6.0.0.rc1/actionpack/CHANGELOG.md
Remove deprecated fragment_cache_key helper in favor of combined_fragment_cache_key.
Remove deprecated methods in ActionDispatch::TestResponse.
#success?, missing? and error? were deprecated in Rails 5.2 in favor of #successful?, not_found? and server_error?.
Deprecate ActionDispatch::Http::ParameterFilter in favor of ActiveSupport::ParameterFilter.
Encode Content-Disposition filenames on send_data and send_file.
Previously, send_data 'data', filename: "\u{3042}.txt" sends "filename=\"\u{3042}.txt\"".
Now it follows RFC 2231 and RFC 5987 and sends "filename=\"%3F.txt\"; filename*=UTF-8''%E3%81%82.txt".
Controller level force_ssl has been deprecated in favor of config.force_ssl.
actiontext
https://github.com/rails/rails/blob/v6.0.0.rc1/actiontext/CHANGELOG.md
- (new module introduced from 6.0.0)
actionview
https://github.com/rails/rails/blob/v6.0.0.rc1/actionview/CHANGELOG.md
npm package renamed from rails-ujs to @rails/ujs.
Remove deprecated image_alt helper.
- Deprecate calling private model methods from view helpers.
Remove ActionView::Helpers::RecordTagHelper.
Disable ActionView::Template finalizers in test environment.
- Don't enforce UTF-8 by default.
Change translation key of submit_tag from module_name_class_name to module_name/class_name.
activejob
https://github.com/rails/rails/blob/v6.0.0.rc1/activejob/CHANGELOG.md
Return false instead of the job instance when enqueue is aborted.
This will be the behavior in Rails 6.1 but it can be controlled now with config.active_job.return_false_on_aborted_enqueue.
- Remove support for Qu gem.
activemodel
https://github.com/rails/rails/blob/v6.0.0.rc1/activemodel/CHANGELOG.md
- Fix date value when casting a multiparameter date hash to not convert from Gregorian date to Julian date.
- Fix year value when casting a multiparameter time hash.
Fix ActiveModel::Serializers::JSON#as_json method for timestamps.
activerecord
https://github.com/rails/rails/blob/v6.0.0.rc1/activerecord/CHANGELOG.md
- Fix query attribute method on user-defined attribute to be aware of typecasted value.
- Deprecate mismatched collation comparison for uniqueness validator.
- Uniqueness validator will no longer enforce case sensitive comparison in Rails 6.1. To continue case sensitive comparison on the case insensitive column, pass case_sensitive: true option explicitly to the uniqueness validator.
Don't allow where with non numeric string matches to 0 values.
Don't allow where with invalid value matches to nil values.
Deprecate using class level querying methods if the receiver scope regarded as leaked. Use klass.unscoped to avoid the leaking scope.
Remove deprecated #set_state from the transaction object.
Remove deprecated #supports_statement_cache? from the database adapters.
Remove deprecated #insert_fixtures from the database adapters.
Remove deprecated ActiveRecord::ConnectionAdapters::SQLite3Adapter#valid_alter_table_type?.
Do not allow passing the column name to sum when a block is passed.
Do not allow passing the column name to count when a block is passed.
Deprecate config.activerecord.sqlite3.represent_boolean_as_integer.
Change SQLite3Adapter to always represent boolean values as integers.
Remove ability to specify a timestamp name for #cache_key.
Remove deprecated ActiveRecord::Migrator.migrations_path=.
Remove deprecated expand_hash_conditions_for_aggregates.
Deprecate passing migrations_paths to connection.assume_migrated_upto_version.
Raise an error instead of scanning the filesystem root when fixture_path is blank.
Deprecate ActiveRecord::Result#to_hash in favor of ActiveRecord::Result#to_a.
Deprecate column_name_length, table_name_length, columns_per_table, indexes_per_table, columns_per_multicolumn_index, sql_query_length, and joins_per_query methods in DatabaseLimits.
Deprecate update_attributes/! in favor of update/!.
activestorage
https://github.com/rails/rails/blob/v6.0.0.rc1/activestorage/CHANGELOG.md
npm package renamed from activestorage to @rails/activestorage.
Replace config.active_storage.queue to config.active_storage.queues.analysis and config.active_storage.queues.purge.
Active Storage error classes now inherit from ActiveStorage::Error instead of StandardError.
activesupport
https://github.com/rails/rails/blob/v6.0.0.rc1/activesupport/CHANGELOG.md
Fix Time#advance to work with dates before 1001-03-07.
Remove the Kernel# override that suppresses ENOENT and accidentally returns nil on Unix systems.
Remove deprecated Module#reachable? method.
Remove deprecated #acronym_regex method from Inflections.
Deprecate ActiveSupport::Multibyte::Unicode#pack_graphemes(array) in favor of array.flatten.pack("U*").
Deprecate ActiveSuppport::Multibyte::Unicode#unpack_graphemes(string) in favor of string.scan(/\X/).map(&:codepoints).
Deprecate ActiveSupport::Multibyte::Chars.consumes? in favor of String#is_utf8?.
Deprecate ActiveSupport::Multibyte::Unicode#normalize and ActiveSuppport::Multibyte::Chars#normalize in favor of String#unicode_normalize.
Deprecate ActiveSupport::Multibyte::Unicode#downcase/upcase/swapcase in favor of String#downcase/upcase/swapcase.
Rename Module#parent, Module#parents, and Module#parent_name to module_parent, module_parents, and module_parent_name.
Deprecate the use of LoggerSilence in favor of ActiveSupport::LoggerSilence.
Deprecate using negative limits in String#first and String#last.
railties
https://github.com/rails/rails/blob/v6.0.0.rc1/railties/CHANGELOG.md
The connection option of rails dbconsole command is deprecated in favor of database option.
Replace chromedriver-helper gem with webdrivers in default Gemfile.
Applications running in :zeitwerk mode that use bootsnap need to upgrade bootsnap to at least 1.4.2.
Remove deprecated after_bundle helper inside plugins template
Remove deprecated support to old config.ru that use the application class as argument of run.
Remove deprecated environment argument from the rails commands.
Remove deprecated capify!.
Remove deprecated config.secret_token.
Remove app/assets and app/javascript from eager_load_paths and autoload_paths.
Deprecate rake routes in favor of rails routes.
Deprecate rake initializers in favor of rails initializers.
Deprecate rake dev:cache in favor of rails dev:cache.
Deprecate rails notes subcommands in favor of passing an annotations argument to rails notes.
rails notes:custom ANNOTATION=custom is deprecated in favor of using rails notes -a custom.
rails notes:optimize is deprecated in favor of using rails notes -a OPTIMIZE.
rails notes:todo is deprecated in favor of using rails notes -a TODO.
rails notes:fixme is deprecated in favor of using rails notes -a FIXME.
Deprecate SOURCE_ANNOTATION_DIRECTORIES environment variable used by rails notes through Rails::SourceAnnotationExtractor::Annotation in favor of using config.annotations.register_directories.
Deprecate rake notes in favor of rails notes.
Deprecate support for using the HOST environment variable to specify the server IP. The BINDING environment variable should be used instead.
Deprecate passing Rack server name as a regular argument to rails server.