Use RBS for indexing Core classes

Gemfile.lock

@@ -12,11 +12,13 @@ PATH
     ruby-lsp (0.17.2)
       language_server-protocol (~> 3.17.0)
       prism (>= 0.29.0, < 0.30)
+      rbs
       sorbet-runtime (>= 0.5.10782)
 
 GEM
   remote: https://rubygems.org/
   specs:
+    abbrev (0.1.2)
     ansi (1.5.0)
     ast (2.4.2)
     builder (3.2.4)
@@ -54,6 +56,8 @@ GEM
     rbi (0.1.13)
       prism (>= 0.18.0, < 1.0.0)
       sorbet-runtime (>= 0.5.9204)
+    rbs (3.4.4)
+      abbrev
     regexp_parser (2.9.2)
     reline (0.5.0)
       io-console (~> 0.5)

lib/ruby_indexer/lib/ruby_indexer/index_rbs.rb

@@ -0,0 +1,45 @@
+# typed: strict
+# frozen_string_literal: true
+
+module RubyIndexer
+  class IndexRbs
+    extend T::Sig
+
+    sig { params(index: Index).void }
+    def initialize(index)
+      @index = index
+    end
+
+    sig { void }
+    def index_core_classes
+      loader = RBS::EnvironmentLoader.new
+      RBS::Environment.from_loader(loader).resolve_type_names
+
+      loader.each_signature do |source, pathname, _buffer, declarations, _directives|
+        process_signature(source, pathname, declarations)
+      end
+    end
+
+    private
+
+    sig { params(source: T.untyped, pathname: Pathname, declarations: T::Array[RBS::AST::Declarations::Base]).void }
+    def process_signature(source, pathname, declarations)
+      declarations.each do |declaration|
+        process_declaration(declaration, pathname)
+      end
+    end
+
+    sig { params(declaration: RBS::AST::Declarations::Base, pathname: Pathname).void }
+    def process_declaration(declaration, pathname)
+      return unless declaration.is_a?(RBS::AST::Declarations::Class)
+
+      nesting = [declaration.name.name.to_s]
+      file_path = pathname.to_s
+      location = RubyIndexer::Location.from_rbs_location(declaration.location)
+      comments = Array(declaration.comment&.string&.lines)
+      parent_class = nil
+      class_entry = Entry::Class.new(nesting, file_path, location, comments, parent_class)
+      @index << class_entry
+    end
+  end
+end

lib/ruby_indexer/lib/ruby_indexer/location.rb

@@ -8,6 +8,19 @@ class Location
     sig { returns(Integer) }
     attr_reader :start_line, :end_line, :start_column, :end_column
 
+    class << self
+      extend T::Sig
+      sig { params(rbs_location: RBS::Location).returns(Location) }
+      def from_rbs_location(rbs_location)
+        new(
+          rbs_location.start_line,
+          rbs_location.end_line,
+          rbs_location.start_column,
+          rbs_location.end_column,
+        )
+      end
+    end
+
     sig do
       params(
         start_line: Integer,

lib/ruby_indexer/ruby_indexer.rb

@@ -11,6 +11,7 @@
 require "ruby_indexer/lib/ruby_indexer/configuration"
 require "ruby_indexer/lib/ruby_indexer/prefix_tree"
 require "ruby_indexer/lib/ruby_indexer/location"
+require "ruby_indexer/lib/ruby_indexer/index_rbs"
 
 module RubyIndexer
   @configuration = T.let(Configuration.new, Configuration)

lib/ruby_indexer/test/index_rbs_test.rb

@@ -0,0 +1,30 @@
+# typed: true
+# frozen_string_literal: true
+
+require_relative "test_case"
+
+module RubyIndexer
+  class IndexRbsTest < TestCase
+    def setup
+      @index = RubyIndexer::Index.new
+      IndexRbs.new(@index).index_core_classes
+    end
+
+    def test_index_core_classes
+      entries = @index["String"]
+      refute_nil(entries)
+      assert_equal(1, entries.length)
+      entry = entries.first
+      assert_match(%r{/gems/rbs-.*/core/string.rbs}, entry.file_path)
+      assert_equal("string.rbs", entry.file_name)
+
+      # Using fixed positions would be fragile, so let's just check some basics.
+      assert_operator(entry.location.start_line, :>, 0)
+      assert_operator(entry.location.end_line, :>, entry.location.start_line)
+      assert_equal(0, entry.location.start_column)
+      assert_operator(entry.location.end_column, :>, 0)
+
+      assert(@index.instance_variable_get(:@entries).key?("String"))
+    end
+  end
+end

lib/ruby_lsp/internal.rb

@@ -18,6 +18,7 @@
 require "prism"
 require "prism/visitor"
 require "language_server-protocol"
+require "rbs"
 
 require "ruby-lsp"
 require "ruby_lsp/base_server"

lib/ruby_lsp/server.rb

@@ -690,6 +690,7 @@ def shutdown
 
     sig { params(config_hash: T::Hash[String, T.untyped]).void }
     def perform_initial_indexing(config_hash)
+      RubyIndexer::IndexRbs.new(@global_state.index).index_core_classes
       # The begin progress invocation happens during `initialize`, so that the notification is sent before we are
       # stuck indexing files
       RubyIndexer.configuration.apply_config(config_hash)

ruby-lsp.gemspec

@@ -20,6 +20,7 @@ Gem::Specification.new do |s|
 
   s.add_dependency("language_server-protocol", "~> 3.17.0")
   s.add_dependency("prism", ">= 0.29.0", "< 0.30")
+  s.add_dependency("rbs")
   s.add_dependency("sorbet-runtime", ">= 0.5.10782")
 
   s.required_ruby_version = ">= 3.0"