find and exists?

Some methods were added to public API in
5b14129d and they should be not part of
the public API.

Raise `ActiveRecord::RangeError` when values that executed are out of range.

9c9fb19b changed the behaviour of the _ids= setters for associations to
raise an AssociationTypeMismatch when unknown IDs are given:

    Class: <ActiveRecord::AssociationTypeMismatch>
    Message: <"Developer(#43811860) expected, got NilClass(#16732720)">

This restores the original ActiveRecord::RecordNotFound exception with a
much clearer error message:

    Class: <ActiveRecord::RecordNotFound>
    Message: <"Couldn't find all Developers with 'id': (1, -9999) [WHERE \"contracts\".\"company_id\" = ?] (found 1 results, but was looking for 2)">

Fixes #25719

Records fetching order is very important for performance if `limit` is
presented. Should not except the order in the case.

And `exists?` replaces select list to `1 AS one` therefore `:distinct`
is useless (`DISTINCT 1 AS one`). And PostgreSQL raises the following
error if `:distinct` and `:order` are used in the same time.

```
ERROR:  for SELECT DISTINCT, ORDER BY expressions must appear in select list
```

All indentation was normalized by rubocop auto-correct at 80e66cc4.
But heredocs was still kept absolute position. This commit aligns
heredocs indentation for consistency.

Currently `CollectionProxy` inherits `Relation` therefore we can use
its own methods rather than delegating to collection association.

Otherwise CollectionProxy's bang methdos cannot respect dirty target.

Style/SpaceBeforeBlockBraces
Style/SpaceInsideBlockBraces
Style/SpaceInsideHashLiteralBraces

Fix all violations in the repository.

`find_nth` is protected method, therefore `offset` has not been passed
anywhere. `find_nth_with_limit_and_offset` is unnecessary anymore
because `offset` has not been passed.

When calling association.find RecordNotFound is now raised with the same argument as when we do it in Record.find (primary_key, id and model).

Some case expressions remain, need to think about those ones.

The current code base is not uniform. After some discussion,
we have chosen to go with double quotes by default.

`FinderMethods#exists?` should return a boolean rather than raising an
exception.

`UniquenessValidator#build_relation` catches a `RangeError` because it
includes type casting due to a string value truncation. But a string
value truncation was removed at #23523 then type casting in
`build_relation` is no longer necessary. aa062318 removes type casting in
`build_relation` then a `RangeError` moves to `relation.exists?`.

This change will remove the catching a `RangeError`.

`construct_relation_for_association_calculations` pass a string value to
`construct_join_dependency` when setting a string value in `from`.
It should not pass a string value, but always `joins_values`.

Related #14834, #19452.

Fixes #24193.

Currently `exists?` does some hackery where it assumes that we can join
onto anything that we passed to `eager_load` or `includes`, which
doesn't work if we are joining onto a polymorphic association.

Actually figuring out if we want to include something would require
knowledge deep within the join dependency module, which is hard to pull
up. The simplest solution is just to pass a flag down that says we're
not actually going to try to eager load any of the data. It's not the
solution I'd like, but that code really needs to be untangled before we
can do much with it.

This is another attempt at 6d5b1fdf which should address the concerns
that led to reverting it in 4ecabed2.

- we are ending sentences properly
- fixing of space issues
- fixed continuity issues in some sentences.

Reverts https://github.com/rails/rails/commit/8fc97d198ef31c1d7a4b9b849b96fc08a667fb02 .
This change reverts making sure we add '.' at end of deprecation sentences.
This is to keep sentences within Rails itself consistent and with a '.' at the end.

We should use #find_or_initialize_by and #find_or_create_by because #first_or_initialize and #first_or_create methods are not the public API

Clarifying this separation and enforcing relation immutability is the
culmination of the previous efforts to remove the mutator method
delegations.

instead of loading the relation into memory

This removes the following warnings.

```
activerecord/lib/active_record/relation/finder_methods.rb:252: warning: ambiguous first argument; put parentheses or a space even after `-' operator
activerecord/lib/active_record/relation/finder_methods.rb:258: warning: ambiguous first argument; put parentheses or a space even after `-' operator
activerecord/lib/active_record/relation/finder_methods.rb:268: warning: ambiguous first argument; put parentheses or a space even after `-' operator
activerecord/lib/active_record/relation/finder_methods.rb:274: warning: ambiguous first argument; put parentheses or a space even after `-' operator
```

This still isn't as separated as I'd like, but it at least moves most of
the burden of alias mapping in one place.

This reverts commit 9f3730a5, reversing
changes made to 2637fb75.

There are additional issues with this commit that need to be addressed
before this change is ready (see #23377). This is a temporary revert in
order for us to have more time to address the issues with that PR,
without blocking the release of beta2.

instead of loading relation

@bogdan pointed out that a `loaded?` relation would not warn that the supplied
offset would be removed. This fixes that oversight.

https://github.com/rails/rails/commit/16a476e4f8f802774ae7c8dca2e59f4e672dc591#commitcomment-15706834

Although this second argument is probably not widely used, and would be
ignored anyway in the loaded? case, this could protect callers from gotchas.

[Ben Woosley & Victor Kmita]

I realized that `first(2)`, etc. was unnecessarily querying for the
records when they were already preloaded. This was because
`find_nth_with_limit` can not know which `@records` to return because
it conflates the `offset` and `index` into a single variable, while
the `@records` only needs the `index` itself to select the proper
record.

Because `find_nth` and `find_nth_with_limit` are public methods, I
instead introduced a private method `find_nth_with_limit_and_offset`
which is called internally and handles the `loaded?` checking.

Once the `offset` argument is removed from `find_nth`,
`find_nth_with_limit_and_offset` can be collapsed into
`find_nth_with_limit`, with `offset` always equal to `offset_index`.