The `ActiveRecord::Fixtures::find_table_name` method was removed from "master" almost a year ago, but it was never deprecated.  Here it comes back, more dead than alive.

See issue #7950.

Nothing should be raised anyway 😄

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

Closes #7551

Thanks @toretore.
https://github.com/rails/rails/commit/9e4c41c903e8e58721f2c41776a8c60ddba7a0a9#commitcomment-2134706

Two threads may be in method_missing at the same time. If so, they might
both try to define the same delegator method.

Such a situation probably wouldn't result in a particularly spectacular
bug as one method would probably just be overridden by an identical
method, but it could cause warnings to pop up. (It could be worse if
method definition is non-atomic in a particular implementation.)

(We will also need this mutex shortly anyway, see #8127.)

We should not need any `serialized_attributes` checks outside `ActiveRecord::AttributeMethods::Serialization` module.

Most apps upgrading from 3.x will have options for mass assigment in
their application.rb and environments/*.rb config files. Rather than
just raising a NoMethodError when copying the config, this commit
adds a warning message until either the protected_attributes gem
is installed or the relevant config options are removed.

These were removed with ActiveRecord::Model in
https://github.com/rails/rails/commit/9e4c41c903e8e58721f2c41776a8c60ddba7a0a9#L15L156

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.

This allows us to avoid hacks like the "return 0 if owner.new_record?"
in #count (which this commit removes).

Also, the relevant foreign key may actually be present even on a new
owner record, in which case we *don't* want a null relation. This logic
is encapsulated in the #null_scope? method.

We also need to make sure that the CollectionProxy is not 'infected'
with the NullRelation module, or else the methods from there will
override the definitions in CollectionProxy, leading to incorrect
results. Hence the nullify: false option to CollectionAssociation#scope.
(This feels a bit nasty but I can't think of a better way.)

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

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

Fixes #5215.

Organized the gemspec files a bit.

 * Made quotes more consistent (single quotes dominated, so I used
   that).
 * Moved license line down a line, separating it logically, and removed
   the extra whitespace before its = operator.
 * Minor whitespace fixes.

This is already handled by #find, it's a duplicate check, since
find_with_ids is not called from anywhere else.