[ci skip] setting :inverse_of works with :as, :through and :polymorphic...

[ci skip] setting :inverse_of works with :as, :through and :polymorphic options, and is needed for bi-directionality with a scope

[ci skip] Remove :conditions opion from association basics guide

This got replaced by scopes.

activerecord/lib/active_record/associations.rb

@@ -1061,12 +1061,6 @@ def association_instance_set(name, association)
       #      belongs_to :dungeon, inverse_of: :evil_wizard
       #    end
       #
-      # There are limitations to <tt>:inverse_of</tt> support:
-      #
-      # * does not work with <tt>:through</tt> associations.
-      # * does not work with <tt>:polymorphic</tt> associations.
-      # * inverse associations for #belongs_to associations #has_many are ignored.
-      #
       # For more information, see the documentation for the +:inverse_of+ option.
       #
       # == Deleting from associations
@@ -1279,6 +1273,9 @@ module ClassMethods
         #   Specify the foreign key used for the association. By default this is guessed to be the name
         #   of this class in lower-case and "_id" suffixed. So a Person class that makes a #has_many
         #   association will use "person_id" as the default <tt>:foreign_key</tt>.
+        #
+        #   If you are going to modify the association (rather than just read from it), then it is
+        #   a good idea to set the <tt>:inverse_of</tt> option.
         # [:foreign_type]
         #   Specify the column used to store the associated object's type, if this is a polymorphic
         #   association. By default this is guessed to be the name of the polymorphic association
@@ -1352,8 +1349,7 @@ module ClassMethods
         #   <tt>:autosave</tt> to <tt>true</tt>.
         # [:inverse_of]
         #   Specifies the name of the #belongs_to association on the associated object
-        #   that is the inverse of this #has_many association. Does not work in combination
-        #   with <tt>:through</tt> or <tt>:as</tt> options.
+        #   that is the inverse of this #has_many association.
         #   See ActiveRecord::Associations::ClassMethods's overview on Bi-directional associations for more detail.
         # [:extend]
         #   Specifies a module or array of modules that will be extended into the association object returned.
@@ -1449,6 +1445,9 @@ def has_many(name, scope = nil, **options, &extension)
         #   Specify the foreign key used for the association. By default this is guessed to be the name
         #   of this class in lower-case and "_id" suffixed. So a Person class that makes a #has_one association
         #   will use "person_id" as the default <tt>:foreign_key</tt>.
+        #
+        #   If you are going to modify the association (rather than just read from it), then it is
+        #   a good idea to set the <tt>:inverse_of</tt> option.
         # [:foreign_type]
         #   Specify the column used to store the associated object's type, if this is a polymorphic
         #   association. By default this is guessed to be the name of the polymorphic association
@@ -1464,6 +1463,9 @@ def has_many(name, scope = nil, **options, &extension)
         #   <tt>:primary_key</tt>, and <tt>:foreign_key</tt> are ignored, as the association uses the
         #   source reflection. You can only use a <tt>:through</tt> query through a #has_one
         #   or #belongs_to association on the join model.
+        #
+        #   If you are going to modify the association (rather than just read from it), then it is
+        #   a good idea to set the <tt>:inverse_of</tt> option.
         # [:source]
         #   Specifies the source association name used by #has_one <tt>:through</tt> queries.
         #   Only use it if the name cannot be inferred from the association.
@@ -1484,8 +1486,7 @@ def has_many(name, scope = nil, **options, &extension)
         #   <tt>:autosave</tt> to <tt>true</tt>.
         # [:inverse_of]
         #   Specifies the name of the #belongs_to association on the associated object
-        #   that is the inverse of this #has_one association. Does not work in combination
-        #   with <tt>:through</tt> or <tt>:as</tt> options.
+        #   that is the inverse of this #has_one association.
         #   See ActiveRecord::Associations::ClassMethods's overview on Bi-directional associations for more detail.
         # [:required]
         #   When set to +true+, the association will also have its presence validated.
@@ -1570,6 +1571,9 @@ def has_one(name, scope = nil, **options)
         #   association will use "person_id" as the default <tt>:foreign_key</tt>. Similarly,
         #   <tt>belongs_to :favorite_person, class_name: "Person"</tt> will use a foreign key
         #   of "favorite_person_id".
+        #
+        #   If you are going to modify the association (rather than just read from it), then it is
+        #   a good idea to set the <tt>:inverse_of</tt> option.
         # [:foreign_type]
         #   Specify the column used to store the associated object's type, if this is a polymorphic
         #   association. By default this is guessed to be the name of the association with a "_type"
@@ -1619,8 +1623,7 @@ def has_one(name, scope = nil, **options)
         #   +after_commit+ and +after_rollback+ callbacks are executed.
         # [:inverse_of]
         #   Specifies the name of the #has_one or #has_many association on the associated
-        #   object that is the inverse of this #belongs_to association. Does not work in
-        #   combination with the <tt>:polymorphic</tt> options.
+        #   object that is the inverse of this #belongs_to association.
         #   See ActiveRecord::Associations::ClassMethods's overview on Bi-directional associations for more detail.
         # [:optional]
         #   When set to +true+, the association will not have its presence validated.
@@ -1789,6 +1792,9 @@ def belongs_to(name, scope = nil, **options)
         #   of this class in lower-case and "_id" suffixed. So a Person class that makes
         #   a #has_and_belongs_to_many association to Project will use "person_id" as the
         #   default <tt>:foreign_key</tt>.
+        #
+        #   If you are going to modify the association (rather than just read from it), then it is
+        #   a good idea to set the <tt>:inverse_of</tt> option.
         # [:association_foreign_key]
         #   Specify the foreign key used for the association on the receiving side of the association.
         #   By default this is guessed to be the name of the associated class in lower-case and "_id" suffixed.

guides/source/association_basics.md

@@ -735,12 +735,9 @@ a.first_name = 'David'
 a.first_name == b.author.first_name # => true
 ```
 
-Active Record supports automatic identification for most associations with standard names. However, Active Record will not automatically identify bi-directional associations that contain any of the following options:
+Active Record supports automatic identification for most associations with standard names. However, Active Record will not automatically identify bi-directional associations that contain a scope or any of the following options:
 
-* `:conditions`
 * `:through`
-* `:polymorphic`
-* `:class_name`
 * `:foreign_key`
 
 For example, consider the following model declarations:
@@ -787,12 +784,6 @@ a.first_name = 'David'
 a.first_name == b.writer.first_name # => true
 ```
 
-There are a few limitations to `:inverse_of` support:
-
-* They do not work with `:through` associations.
-* They do not work with `:polymorphic` associations.
-* They do not work with `:as` associations.
-
 Detailed Association Reference
 ------------------------------
 
@@ -1012,7 +1003,7 @@ When we execute `@user.todos.create` then the `@todo` record will have its
 
 ##### `:inverse_of`
 
-The `:inverse_of` option specifies the name of the `has_many` or `has_one` association that is the inverse of this association. Does not work in combination with the `:polymorphic` options.
+The `:inverse_of` option specifies the name of the `has_many` or `has_one` association that is the inverse of this association.
 
 ```ruby
 class Author < ApplicationRecord
@@ -1066,7 +1057,8 @@ There may be times when you wish to customize the query used by `belongs_to`. Su
 ```ruby
 class Book < ApplicationRecord
   belongs_to :author, -> { where active: true },
-                        dependent: :destroy
+                        dependent: :destroy,
+                        inverse_of: :books
 end
 ```
 
@@ -1082,8 +1074,8 @@ You can use any of the standard [querying methods](active_record_querying.html)
 The `where` method lets you specify the conditions that the associated object must meet.
 
 ```ruby
-class book < ApplicationRecord
-  belongs_to :author, -> { where active: true }
+class Book < ApplicationRecord
+  belongs_to :author, -> { where active: true }, inverse_of: :books
 end
 ```
 
@@ -1299,7 +1291,7 @@ TIP: In any case, Rails will not create foreign key columns for you. You need to
 
 ##### `:inverse_of`
 
-The `:inverse_of` option specifies the name of the `belongs_to` association that is the inverse of this association. Does not work in combination with the `:through` or `:as` options.
+The `:inverse_of` option specifies the name of the `belongs_to` association that is the inverse of this association.
 
 ```ruby
 class Supplier < ApplicationRecord
@@ -1337,7 +1329,7 @@ There may be times when you wish to customize the query used by `has_one`. Such
 
 ```ruby
 class Supplier < ApplicationRecord
-  has_one :account, -> { where active: true }
+  has_one :account, -> { where active: true }, inverse_of: :supplier
 end
 ```
 
@@ -1694,7 +1686,7 @@ TIP: In any case, Rails will not create foreign key columns for you. You need to
 
 ##### `:inverse_of`
 
-The `:inverse_of` option specifies the name of the `belongs_to` association that is the inverse of this association. Does not work in combination with the `:through` or `:as` options.
+The `:inverse_of` option specifies the name of the `belongs_to` association that is the inverse of this association.
 
 ```ruby
 class Author < ApplicationRecord