- Remove
```
* Namespace error pages' CSS selectors to stop the styles from bleeding
into other pages when using Turbolinks.
([Pull Request](https://github.com/rails/rails/pull/28814))
```
since it was backported to
`5-1-stable` by 50d5baf7ed
and
`5-0-stable` by d1c4a39ed7.
- Remove
```
* Allow irb options to be passed from `rails console` command.
([Pull Request](https://github.com/rails/rails/pull/29010))
```
since it was backported to
`5-1-stable` by e91b48348c.
- Remove
```
* Load environment file in `dbconsole` command.
([Pull Request](https://github.com/rails/rails/pull/29725))
```
since it was backported to
`5-1-stable` by 7f9342877a.
- Remove
```
* Gemfile for new apps: upgrade redis-rb from ~> 3.0 to 4.0.
([Pull Request](https://github.com/rails/rails/pull/30748))
```
since it was backported to
`5-1-stable` by 3789531151.
- Remove
```
* Fix minitest rails plugin.
The custom reporters are added only if needed.
This will fix conflicts with others plugins.
([Commit](ac99916fcf))
```
since it was backported to
`5-1-stable` by caa76956d3.
- Remove
```
* Add support for compatibility with redis-rb gem for 4.0 version.
([Pull Request](https://github.com/rails/rails/pull/30748))
```
since it was backported to
`5-1-stable` by 3789531151.
- Remove
```
* Add `action_controller_api` and `action_controller_base` load hooks to be
called in `ActiveSupport.on_load`.
([Pull Request](https://github.com/rails/rails/pull/28402))
```
since it was backported to
`5-1-stable` by b9a5fd706a.
- Remove
```
* `driven_by` now registers poltergeist and capybara-webkit.
([Pull Request](https://github.com/rails/rails/pull/29315))
```
since it was backported to
`5-1-stable` by c5dd45119a.
- Remove
```
* Fallback `ActionController::Parameters#to_s` to `Hash#to_s`.
([Pull Request](https://github.com/rails/rails/pull/29630))
```
since it was backported to
`5-1-stable` by c1014e435d
and
`5-0-stable` by 0e71fc3040.
- Remove
```
* Make `take_failed_screenshot` work within engine.
([Pull Request](https://github.com/rails/rails/pull/30421))
```
since it was backported to
`5-1-stable` by 595a231029.
- Remove
```
* Fix optimized url helpers when using relative url root.
([Pull Request](https://github.com/rails/rails/pull/31261))
```
since it was backported to
`5-1-stable` by e9b77953a2.
- Remove
```
* Update `distance_of_time_in_words` helper to display better error messages
for bad input.
([Pull Request](https://github.com/rails/rails/pull/20701))
```
since it was backported to
`5-1-stable` by 2c97fbf650.
- Remove
```
* Generate field ids in `collection_check_boxes` and
`collection_radio_buttons`.
([Pull Request](https://github.com/rails/rails/pull/29412))
```
since it was backported to
`5-1-stable` by 2d8c10a7b1.
- Remove
```
* Fix issues with scopes and engine on `current_page?` method.
([Pull Request](https://github.com/rails/rails/pull/29503))
```
since it was backported to
`5-1-stable` by 2135daf0d5.
- Remove
```
* Bring back proc with arity of 1 in `ActionMailer::Base.default` proc
since it was supported in Rails 5.0 but not deprecated.
([Pull Request](https://github.com/rails/rails/pull/30391))
```
since it was backported to
`5-1-stable` by b2bedb1492.
- Remove
```
* Add type caster to `RuntimeReflection#alias_name`.
([Pull Request](https://github.com/rails/rails/pull/28961))
```
since it was backported to
`5-1-stable` by f644e7a6fd.
- Remove
```
* Loading model schema from database is now thread-safe.
([Pull Request](https://github.com/rails/rails/pull/29216))
```
since it was backported to
`5-1-stable` by 02926cfff6.
and
`5-0-stable` by 84bcfe5a6a
- Remove
```
* Fix destroying existing object does not work well when optimistic locking
enabled and `locking_column` is null in the database.
([Pull Request](https://github.com/rails/rails/pull/28926))
```
since it was backported to
`5-1-stable` by e498052c52.
- Remove
```
* `ActiveRecord::Persistence#touch` does not work well
when optimistic locking enabled and `locking_column`,
without default value, is null in the database.
([Pull Request](https://github.com/rails/rails/pull/28914))
```
since it was backported to
`5-1-stable` by 1e2f63db78.
- Remove
```
* Previously, when building records using a `has_many :through` association,
if the child records were deleted before the parent was saved,
they would still be persisted. Now, if child records are deleted
before the parent is saved on a `has_many :through` association,
the child records will not be persisted.
([Pull Request](https://github.com/rails/rails/pull/29593))
```
since it was backported to
`5-1-stable` by a22c39e9cc.
- Remove
```
* Query cache was unavailable when entering the `ActiveRecord::Base.cache`
block without being connected.
([Pull Request](https://github.com/rails/rails/pull/29609))
```
since it was backported to
`5-1-stable` by fd6c8cdfe6
and
`5-0-stable` by 9f2532bb16.
- Remove
```
* `Relation#joins` is no longer affected by the target model's
`current_scope`, with the exception of `unscoped`.
([Commit](5c71000d08))
```
since it was backported to
`5-1-stable` by 3630d6354c.
- Remove
```
* Fix `unscoped(where: [columns])` removing the wrong bind values.
([Pull Request](https://github.com/rails/rails/pull/29780))
```
since it was backported to
`5-1-stable` by d378fcb254.
- Remove
```
* When a `has_one` association is destroyed by `dependent: destroy`,
`destroyed_by_association` will now be set to the reflection, matching the
behaviour of `has_many` associations.
([Pull Request](https://github.com/rails/rails/pull/29855))
```
since it was backported to
`5-1-stable` by 8254a8be81.
- Remove
```
* Fix `COUNT(DISTINCT ...)` with `ORDER BY` and `LIMIT`
to keep the existing select list.
([Pull Request](https://github.com/rails/rails/pull/29848))
```
since it was backported to
`5-1-stable` by 0e8d4edd56.
- Remove
```
* Ensure `sum` honors `distinct` on `has_many :through` associations.
([Commit](566f1fd068))
```
since it was backported to
`5-1-stable` by c0a1dc2561.
- Remove
```
* Fix `COUNT(DISTINCT ...)` for `GROUP BY` with `ORDER BY` and `LIMIT`.
([Commit](5668dc6b18))
```
since it was backported to
`5-1-stable` by 87ca68e76e.
- Remove
```
* MySQL: Don't lose `auto_increment: true` in the `db/schema.rb`.
([Commit](9493d45535))
```
since it was backported to
`5-1-stable` by 8b6e694e5f.
- Remove
```
* Fix longer sequence name detection for serial columns.
([Pull Request](https://github.com/rails/rails/pull/28339))
```
since it was backported to
`5-1-stable` by af9c1707ad
and
`5-0-stable` by 7025b1d8eb.
- Remove
```
* Fix `bin/rails db:setup` and `bin/rails db:test:prepare` create wrong
ar_internal_metadata's data for a test database.
([Pull Request](https://github.com/rails/rails/pull/30579))
```
since it was backported to
`5-1-stable` by bb67b5f278
and
`5-0-stable` by 60437e6d3c.
- Remove
```
* Fix conflicts `counter_cache` with `touch: true` by optimistic locking.
([Pull Request](https://github.com/rails/rails/pull/31405))
```
since it was backported to
`5-1-stable` by 5236ddaf35.
- Remove
```
* Fix `count(:all)` to correctly work `distinct` with custom SELECT list.
([Commit](c6cd9a59f2))
```
since it was backported to
`5-1-stable` by 6beb4de7dd.
- Remove
```
* Fix to invoke callbacks when using `update_attribute`.
([Commit](732aa34b6e))
```
since it was backported to
`5-1-stable` by 6346683bc5.
- Remove
```
* Use `count(:all)` in `HasManyAssociation#count_records` to prevent invalid
SQL queries for association counting.
([Pull Request](https://github.com/rails/rails/pull/27561))
```
since it was backported to
`5-1-stable` by eef3c89e3b.
- Remove
```
* Fix `count(:all)` with eager loading and having an order other than
the driving table.
([Commit](ebc09ed9ad))
```
since it was backported to
`5-1-stable` by 6df9b69b23.
- Remove
```
* PostgreSQL: Allow pg-1.0 gem to be used with Active Record.
([Pull Request](https://github.com/rails/rails/pull/31671))
```
since it was backported to
`5-1-stable` by a9c06f61d5.
- Remove
```
* Fix that after commit callbacks on update does not triggered
when optimistic locking is enabled.
([Commit](7f9bd034c4))
```
since it was backported to
`5-1-stable` by aaee10e6e4.
- Remove
```
* Fix regression in numericality validator when comparing Decimal and Float
input values with more scale than the schema.
([Pull Request](https://github.com/rails/rails/pull/28584))
```
since it was backported to
`5-1-stable` by 5b1c3e5a8b.
Note that there was incorrect link to PR,
original PR is https://github.com/rails/rails/pull/29249.
- Remove
```
* Fix to working before/after validation callbacks on multiple contexts.
([Pull Request](https://github.com/rails/rails/pull/31483))
```
since it was backported to
`5-1-stable` by 0f7046a7f8.
- Remove
```
* Fix implicit coercion calculations with scalars and durations.
([Pull Request](https://github.com/rails/rails/pull/29163),
[Pull Request](https://github.com/rails/rails/pull/29971))
```
since it was backported to
`5-1-stable` by 51ea27c04c,
4d82e2aad9.
- Remove
```
* Fix modulo operations involving durations.
([Commit](a54e13bd2e))
```
since it was backported to
`5-1-stable` by 233fa7eab3.
- Remove
```
* Return all mappings for a timezone identifier in `country_zones`.
([Commit](cdce6a709e))
```
since it was backported to
`5-1-stable` by 0222ebbe06.
- Remove
```
* Add support for compatibility with redis-rb gem for 4.0 version.
([Pull Request](https://github.com/rails/rails/pull/30748))
```
since it was backported to
`5-1-stable` by 3789531151.
Related to #32252.
Related to #32222, https://github.com/rails/rails/pull/32222#discussion_r174256536.
Follow up a489cc81b6.
- Add a description of major features in Rails 5.2.
- Add a reference to Pull Request/Commit to every entry in CHANGELOGs,
note that some of them combined.
- Add section "Ruby on Rails Guides" with notable changes.
- Note that
- Skipped this since encrypted secrets are already on the way out.
```
* Add `rails secrets:show` command.
([Pull Request](https://github.com/rails/rails/pull/29695))
```
- Skipped this since it was backported all the way to 5-0-stable.
```
* Make Rails' test runner work better with minitest plugins.
([Pull Request](https://github.com/rails/rails/pull/29572))
```
Thanks to everyone who has been working on Rails 5.2! <3
Currently, generation of guide is an error in `5_2_release_notes.html`.
```
$ bunele exec rake guides:generate:html
Generating 5_2_release_notes.md as 5_2_release_notes.html
rails/guides/rails_guides/markdown.rb:44:in `dom_id': undefined method `[]' for nil:NilClass (NoMethodError)
from rails/guides/rails_guides/markdown.rb:106:in `block (2 levels) in generate_structure'
```
It seems that it is an error because there are multiple
`active-storage` anchors.
Since Active Storage is a Major feature, it is unnecessary to show
CHANGELOGs, so remove from `Incompatibilities` section.
