Ruby: namespaced-constant receivers (A::B.call) get no references edge, so the class has 0 callers #2503

Summary

A Ruby call whose receiver is a namespaced constant (Billing::ChargeCard.call(...)) gets no references edge to the class, so the class shows 0 callers / 0 dependents even though it is called from many places. #1110 added the receiver references edge for a bare constant (ChargeCard.call), but the scope_resolution form is excluded.

This pattern is the norm in Rails apps that organize service objects or commands under namespaces (app/services/billing/charge_card.rb → Billing::ChargeCard.call(...)). In the Rails codebase we evaluated (v1.6.2), it accounts for roughly 1.6k call sites, and callers / impact / codegraph_explore returned nothing for any of the classes we checked.

Repro (v1.6.2)

# app/services/billing/charge_card.rb
module Billing
  class ChargeCard
    def self.call(**kw) = new(**kw).call
    def initialize(amount:) = @amount = amount
    def call = @amount
  end
end

# app/services/checkout/complete.rb
module Checkout
  class Complete
    def call
      Billing::ChargeCard.call(amount: 1)   # namespaced receiver: no edge
    end
  end
end

# app/services/billing/refund.rb
module Billing
  class Refund
    def call
      ChargeCard.call(amount: 2)            # bare receiver: edge recorded
    end
  end
end

Actual output (v1.6.2, fresh codegraph init):

$ codegraph callers ChargeCard
Callers of "ChargeCard" (1):

class Billing::ChargeCard (ruby) — app/services/billing/charge_card.rb:2
method      call [references]
  app/services/billing/refund.rb:3          <- only the bare-receiver caller

$ codegraph callees call -f checkout/complete.rb
Callees of "call" (0):

method Checkout::Complete::call (ruby) — app/services/checkout/complete.rb:3
ℹ No callees found for "call"

$ codegraph callees call -f billing/refund.rb
Callees of "call" (2):
...
class       ChargeCard [references]
  app/services/billing/charge_card.rb:2

Expected: Checkout::Complete#call is listed as a caller of Billing::ChargeCard, the same as Billing::Refund#call.

Root cause

codegraph-kernel/src/ruby.rs emits the extra receiver references ref only when the receiver node kind is constant. The comment says so explicitly:

// Capitalized constant receiver (`Klass.static_call`, `RETRY_MAX.times`)
// → an ADDITIONAL references ref at the RECEIVER's position.
// (scope_resolution receivers get none — type ≠ constant.)
if !skip && receiver.kind() == "constant" {

Suggested fix

Also emit the references ref when receiver.kind() == "scope_resolution" and its last segment is capitalized. Either:

• reference the full qualified name (Billing::ChargeCard), resolving against the class node's qualified name, which is the precise option since last segments like Create / Update repeat across namespaces; or
• reference the last segment, mirroring how NS::Widget.new → instantiates Widget is already handled a few lines above (L796-L811), and let the resolver disambiguate.

The first is preferable for Rails/Zeitwerk codebases, where the fully qualified constant maps one-to-one to a file.