Merge pull request #14095 from rails/rm-scopes

Document `default_scope` changes

3 files changed, 85 insertions, 12 deletions

diff --git a/guides/source/4_1_release_notes.md b/guides/source/4_1_release_notes.md
index 8fcfc71351..a0b143d74c 100644
--- a/guides/source/4_1_release_notes.md
+++ b/guides/source/4_1_release_notes.md
@@ -453,6 +453,12 @@ for detailed changes.
 
 ### Notable changes
 
+* Default scopes are no longer overriden by chained conditions.
+
+  Before this change when you defined a `default_scope` in a model
+  it was overriden by chained conditions in the same field. Now it
+  is merged like any other scope. [More Details](upgrading_ruby_on_rails.html#changes-on-default-scopes).
+
 * Added `ActiveRecord::Base.to_param` for convenient "pretty" URLs derived from
   a model's attribute or
   method. ([Pull Request](https://github.com/rails/rails/pull/12891))
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md
index d164b08d93..4900f176a6 100644
--- a/guides/source/active_record_querying.md
+++ b/guides/source/active_record_querying.md
@@ -707,7 +707,7 @@ You can additionally unscope specific where clauses. For example:
 
 ```ruby
 Post.where(id: 10, trashed: false).unscope(where: :id)
-# => SELECT "posts".* FROM "posts" WHERE trashed = 0
+# SELECT "posts".* FROM "posts" WHERE trashed = 0
 ```
 
 A relation which has used `unscope` will affect any relation it is
@@ -715,7 +715,7 @@ merged in to:
 
 ```ruby
 Post.order('id asc').merge(Post.unscope(:order))
-# => SELECT "posts".* FROM "posts"
+# SELECT "posts".* FROM "posts"
 ```
 
 ### `only`
@@ -1242,26 +1242,26 @@ class User < ActiveRecord::Base
 end
 
 User.active.inactive
-# => SELECT "users".* FROM "users" WHERE "users"."state" = 'active' AND "users"."state" = 'inactive'
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'active' AND "users"."state" = 'inactive'
 ```
 
 We can mix and match `scope` and `where` conditions and the final sql
-will have all conditions joined with `AND` .
+will have all conditions joined with `AND`.
 
 ```ruby
 User.active.where(state: 'finished')
-# => SELECT "users".* FROM "users" WHERE "users"."state" = 'active' AND "users"."state" = 'finished'
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'active' AND "users"."state" = 'finished'
 ```
 
 If we do want the `last where clause` to win then `Relation#merge` can
-be used .
+be used.
 
 ```ruby
 User.active.merge(User.inactive)
-# => SELECT "users".* FROM "users" WHERE "users"."state" = 'inactive'
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'inactive'
 ```
 
-One important caveat is that `default_scope` will be overridden by
+One important caveat is that `default_scope` will be prepended in
 `scope` and `where` conditions.
 
 ```ruby
@@ -1272,16 +1272,16 @@ class User < ActiveRecord::Base
 end
 
 User.all
-# => SELECT "users".* FROM "users" WHERE "users"."state" = 'pending'
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending'
 
 User.active
-# => SELECT "users".* FROM "users" WHERE "users"."state" = 'active'
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' AND "users"."state" = 'active'
 
 User.where(state: 'inactive')
-# => SELECT "users".* FROM "users" WHERE "users"."state" = 'inactive'
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' AND "users"."state" = 'inactive'
 ```
 
-As you can see above the `default_scope` is being overridden by both
+As you can see above the `default_scope` is being merged in both
 `scope` and `where` conditions.
 
 
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index f28f6dc576..76722c9ea9 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -262,6 +262,73 @@ authors = Author.where(name: 'Hank Moody').to_a
 authors.compact!
 ```
 
+### Changes on Default Scopes
+
+Default scopes are no longer overriden by chained conditions.
+
+In previous versions when you defined a `default_scope` in a model
+it was overriden by chained conditions in the same field. Now it
+is merged like any other scope.
+
+Before:
+
+```ruby
+class User < ActiveRecord::Base
+  default_scope { where state: 'pending' }
+  scope :active, -> { where state: 'active' }
+  scope :inactive, -> { where state: 'inactive' }
+end
+
+User.all
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending'
+
+User.active
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'active'
+
+User.where(state: 'inactive')
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'inactive'
+```
+
+After:
+
+```ruby
+class User < ActiveRecord::Base
+  default_scope { where state: 'pending' }
+  scope :active, -> { where state: 'active' }
+  scope :inactive, -> { where state: 'inactive' }
+end
+
+User.all
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending'
+
+User.active
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' AND "users"."state" = 'active'
+
+User.where(state: 'inactive')
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' AND "users"."state" = 'inactive'
+```
+
+To get the previous behavior it is needed to explicitly remove the
+`default_scope` condition using `unscoped`, `unscope`, `rewhere` or
+`except`.
+
+```ruby
+class User < ActiveRecord::Base
+  default_scope { where state: 'pending' }
+  scope :active, -> { unescope(where: :state).where(state: 'active') }
+  scope :inactive, -> { rewhere state: 'inactive' }
+end
+
+User.all
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending'
+
+User.active
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'active'
+
+User.inactive
+# SELECT "users".* FROM "users" WHERE "users"."state" = 'inactive'
+```
+
 Upgrading from Rails 3.2 to Rails 4.0
 -------------------------------------