How does a Model have access to a class method like where?

[AlvesJorge]

As per the docs, one should add include Mongoid::Document to their class to have any new document saved to the database, and overall have the ORM working as intended.
So far so good, my app works, no problem there.

class Band
 include Mongoid::Document
end

However my question is, according to this and other stack overflow posts, include makes the included class methods available to the target class instances, but it shouldn't do anything about adding the included class methods to the target class itself as class methods.
So how can can we use something like Band.where("...") if .where isn't being inherited?

Obviously it is being inherited I'm just trying to understand how, and where I went wrong with my logic :) Thanks

Context: My LSP can't pick up the where method on a class, so I have to go on a rabbit hole finding out why

[jamis]

Mongoid makes very heavy use of delegation and metaprogramming. It also uses ActiveSupport::Concern (from Rails) so that you can define class methods in a module that get applied when the module is included.

Looking specifically at the #where method will give you a bit of a taste of just how convoluted this gets. :)

• The #where method is defined on the Mongoid::Criteria class: here
• The #where method is included in the set of methods that Mongoid::Criteria::Queryable::Selectable declares as "forwardable", here
• Mongoid::Document includes Mongoid::Composable (here), which extends Mongoid::Findable (here).
• Mongoid::Findable delegates those forwardable defined in Mongoid::Criteria::Queryable::Selectable to with_default_scope (here).
• Mongoid::Composable (which you'll recall is included by Mongoid::Document) also includes Mongoid::Scopable (here), and with_default_scope is declared as a class method of Mongoid::Scopable (here).
• #with_default_scope calls queryable.with_default_scope, and #queryable is also a class method of Mongoid::Scopable (here).
• #queryable returns the active (in-scope) Mongoid::Criteria instance, or if no such instance is currently active, it instantiates a new Mongoid::Criteria instance (here).
• Digging further, we see that Mongoid::Criteria#with_default_scope (here) creates and returns a clone of the current criteria object, possibly initializing it with default scope conditions.

So, putting that all together, we can see that Model.where is delegated to the #where method of whatever Mongoid::Criteria instance is currently in scope (or a new instance if no such object exists). It's quite convoluted, and while it is one of the most complex paths in Mongoid right now (I believe), there are plenty of similar examples throughout the code base.

[AlvesJorge]

Thank you for such a detailed answer!