Making this change revealed several subtle bugs related to models with
no primary key, and anonymous classes. These have been fixed as well,
with regression tests added.
This will make it less painful to add additional properties, which
should persist across writes, such as `name`.
Conflicts:
activerecord/lib/active_record/attribute_set.rb
Moved `Builder` to its own file, as it started looking very weird once I
added private methods to the `AttributeSet` class and the `Builder`
class started to grow.
Would like to refactor `fetch_value` to change to
```ruby
self[name].value(&block)
```
But that requires the attributes to know about their name, which they
currently do not.
Adding `# :nodoc:` to the parent `class` / `module` is not going
to ignore nested classes or modules.
There is a modifier `# :nodoc: all` but sadly the containing class
or module will continue to be in the docs.
/cc @sgrif
There's a lot more that can be moved to these, but this felt like a good
place to introduce the object. Plans are:
- Remove all knowledge of type casting from the columns, beyond a
reference to the cast_type
- Move type_cast_for_database to these objects
- Potentially make them mutable, introduce a state machine, and have
dirty checking handled here as well
- Move `attribute`, `decorate_attribute`, and anything else that
modifies types to mess with this object, not the columns hash
- Introduce a collection object to manage these, reduce allocations, and
not require serializing the types
