Support on_call_node_leave events in index enhancement

[st0012]

Motivation

For addons to build data structure that mimic scopes defined by DSLs (e.g. RSpec's context blocks), Ruby LSP's index enhancement needs to allow listening to on_call_node_leave events too.

Implementation

1. Convert Enhancement to a class instead of a module and change its interfaces
2. Rename on_call_node to on_call_node_enter so it aligns with Prism's dispatcher event name and will allow a on_call_node_leave event too
3. Support on_call_node_leave event to index enhancement

Automated Tests

Manual Tests

[andyw8]

We'll need to also update jekyll/add-ons.markdown.

[st0012]

We'll need to also update jekyll/add-ons.markdown.

Done 👍

[vinistock]

Nice

[andyw8]

I noticed when updating ruby-lsp-rails in Shopify/ruby-lsp-rails#495 that it's a bit odd to pass @index to @index. What if we change this so that we just pass the class, i.e. @index.register_enhancement(MyIndexingEnhancement), and let register_enhancement instantiate it?

[st0012]

I thought about that but it means addon authors will lose the ability to customize their enhancements' constructor and the data it could hold.

[vinistock]

Why is it odd to pass the index?

[andyw8]

For the basic case it seems like unnecessary argument passing, when you could do something like:

@index.register_enhancement(MyIndexingEnhancement)

with

def register_enhancement(enhancement_class)
  @enhancements << enhancement_class.new(self)
end

but as @st0012 says, it does allow for more flexibility.