See issue #7950.

Nothing should be raised anyway 😄

Thanks @spastorino ❤
https://github.com/rails/rails/pull/8202/files#r2112067

Closes #7551

Rather than just changing it and hoping for the best.

Requested by @jeremy:

https://github.com/rails/rails/commit/ba1544d71628abff2777c9c514142d7e9a159111#commitcomment-2106059

So that the scope may be a NullRelation and return a result without
executing a query.

Fixes #7928

Fixes #8102.

I couldn't find a nicer way to deal with this than delegate the call to
 #scope, which will be a NullRelation when we want it to be.

For example, the following should not run any query on the database:

Post.new.comments.where(body: 'omg').to_a # => []

Fixes #5215.

Also refactor the test a bit.

message

This was there due historical reasons since
7dc45818 to give the user the
possibility to create unique indexes passing "UNIQUE" as the third
argument

Closes #8104

This reverts commit 3b890520.

Reason: changes made to a test, albeit in commented lines - non-uniform
change.

[ci skip]

When calling first(n) or last(n) in a collection, Active Record was
improperly trying to set the inverse of instance in case that option
existed. This change was introduced by
fdf4eae5.

In such cases we don't need to do that "manually", since the way
collection will be loaded will already handle that, so we just skip
setting the inverse association when any argument is given to
first(n)/last(n).

The test included ensures that these scenarios will have the inverse of
instance set properly.

Fixes #8087, Closes #8094.

Squashed cherry-pick from d37d40b2 and c368b660.

Conflicts:
	activerecord/CHANGELOG.md
	activerecord/lib/active_record/associations/collection_association.rb

Public method `attributes_before_type_cast` used to return internal AR structure (ActiveRecord::AttributeMethods::Serialization::Attribute), patch fixes this. Now behaves like `read_attribute_before_type_cast` and returns unserialised values.

This can occur if the user is using :integer columns to store boolean
values. Now we are handling the boolean values but it still raises if
the value can't type cast to integer and is not a boolean. See #7509.

Fixes #8067.

Conflicts:
	activerecord/CHANGELOG.md

Checking for the constant doesn't work

Didn't work before because it updated the model-in-memory first, so the DB query couldn't find the record.