<%= cache post do %>

# ActionView::Helpers::CacheHelper

def cache(name = {}, options = {}, &block)
  if controller.respond_to?(:perform_caching) && controller.perform_caching
    name_options = options.slice(:skip_digest, :virtual_path)
    safe_concat(fragment_for(cache_fragment_name(name, name_options), options, &block))
  else
    yield
  end

  nil
end

name = {} # --> Is the Post I'm caching
options = {} # Is empty
controller = PostsController
controller.respond_to?(:perform_caching) # => TRUE
controller.perform_caching # => I'm almost certain it's a rails config that's set to true

INTO THE IF STATEMENT
name_options = options.slice(:skip_digest, :virtual_path) # => empty hash since 
																															# options  is empty

BREAKING DOWN CACHE_FRAGMENT_NAME ===============
def cache_fragment_name(name = {}, skip_digest: nil, virtual_path: nil, digest_path: nil)
  if skip_digest
    name
  else
    fragment_name_with_digest(name, virtual_path, digest_path)
  end
end
cache_fragment_name(name, name_options)

name = post instance is still the post we're trying to cache
virtual_path = nil
digest_path = nil

BREAKING DOWN ==========================
# fragment_name_with_digest(name, virtual_path, digest_path)
def fragment_name_with_digest(name, virtual_path, digest_path)
  virtual_path ||= @virtual_path

  if virtual_path || digest_path
    name = controller.url_for(name).split("://").last if name.is_a?(Hash)

    digest_path ||= digest_path_from_template(@current_template)

    [ digest_path, name ]
  else
    name
  end
end

virtual_path is set to whatever @virtual path is. In this case:
@virtual_path = "posts/_post"  !--- component ----!  '/post_component'
We also have access to:
@current_template               !---component----! 
	.locals =  post               !---component----! no method error (this is not a template with locals)
	.short_identifier = 'app/views/posts/_post.html.erb !---component----! (this is not a template)
	.class = ActionView::Template  !---component----! PostComponent.rb
	.virtual_path = "posts/_post"  !---component----! "/post_component"

--- inside -> if virtual_path || digest_path
name is not a hash, name is still the post instance

BREAKING DOWN =====================
#digest_path_from_template

def digest_path_from_template(template) # :nodoc:
  digest = Digestor.digest(name: template.virtual_path, format: template.format, finder: lookup_context, dependencies: view_cache_dependencies)

  if digest.present?
    "#{template.virtual_path}:#{digest}"
  else
    template.virtual_path
  end
end

template is an ActionView::Template, the same as @current_template !---component----! template is a PostComponent.rb instance
template.short_identifier = 'app/views/posts/_post.html.erb' # for reference
The result from Digestor.digest(...) is 586517e78be822fa6f6e60856e002275

!---component----!
COMPONENT'S RESULT FROM DIGESTOR IS AN EMPTY STRING!!!
!---component----!

"#{template.virtual_path}:#{digest}" == 'posts/_post:586517e78be822fa6f6e60856e002275'

RETURNED TO fragment_name_with_digest ==============
[ digest_path, name ] = [ 'posts/_post:586517e78be822fa6f6e60856e002275', the_same_post_were_using_to_cache ] 

RETURNED TO `cache`=========================
GOING INTO ================================
  fragment_for with the return from cache_fragment_name 
	which is the return of fragment_name_with_digest, ergo: 
  [ digest_path, name ] = [ 'posts/_post:586517e78be822fa6f6e60856e002275', the_same_post_were_using_to_cache ] 

def fragment_for(name = {}, options = nil, &block)
  if content = read_fragment_for(name, options)
    @view_renderer.cache_hits[@virtual_path] = :hit if defined?(@view_renderer)
    content
  else
    @view_renderer.cache_hits[@virtual_path] = :miss if defined?(@view_renderer)
    write_fragment_for(name, options, &block)
  end
end

content = read_fragment_for(name, options) is nil because there's nothing cached
in the db at this point. 

@view_renderer is defined => ActionView::Renderer
	.lookup_context => 
		.view_paths
			.paths => app/views, actiontext/app/views, actionmailbox/app/views

write_fragment_for(name, options, &block) #=> will write the cache. 
# I'll stop here since I don't think writing the cache has anyting to do with
# the view-component caching issue