Use Rubydex for method hover (#4099)

Author: vinistock

lib/ruby_lsp/listeners/hover.rb

@@ -15,7 +15,6 @@ class Hover
       def initialize(response_builder, global_state, uri, node_context, dispatcher, sorbet_level, position) # rubocop:disable Metrics/ParameterLists
         @response_builder = response_builder
         @global_state = global_state
-        @index = global_state.index #: RubyIndexer::Index
         @graph = global_state.graph #: Rubydex::Graph
         @type_inferrer = global_state.type_inferrer #: TypeInferrer
         @path = uri.to_standardized_path #: String?
@@ -457,21 +456,22 @@ def handle_method_hover(message, inherited_only: false)
         type = @type_inferrer.infer_receiver_type(@node_context)
         return unless type
 
-        methods = @index.resolve_method(message, type.name, inherited_only: inherited_only)
-        return unless methods
+        owner = @graph[type.name]
+        return unless owner.is_a?(Rubydex::Namespace)
 
-        first_method = methods.first #: as !nil
-        return unless method_reachable_from_call_site?(first_method, type, @graph, @node_context)
+        method = owner.find_member("#{message}()", only_inherited: inherited_only)
+        return unless method.is_a?(Rubydex::Method)
+        return unless method_reachable_from_call_site?(method, type, @graph, @node_context)
 
-        title = "#{message}#{first_method.decorated_parameters}"
-        title << first_method.formatted_signatures
+        title = +"#{message}#{method.decorated_parameters}"
+        title << method.formatted_signatures
 
         if type.is_a?(TypeInferrer::GuessedType)
           title << "\n\nGuessed receiver: #{type.name}"
           @response_builder.push("[Learn more about guessed types](#{GUESSED_TYPES_URL})\n", category: :links)
         end
 
-        categorized_markdown_from_index_entries(title, methods).each do |category, content|
+        categorized_markdown_from_definitions(title, method.definitions).each do |category, content|
           @response_builder.push(content, category: category)
         end
       end

lib/ruby_lsp/listeners/signature_help.rb

@@ -33,14 +33,7 @@ def on_call_node_enter(node)
         target_method = owner.find_member("#{message}()")
         return unless target_method.is_a?(Rubydex::Method)
 
-        signatures = target_method.definitions.flat_map do |defn|
-          case defn
-          when Rubydex::MethodDefinition, Rubydex::MethodAliasDefinition
-            defn.signatures
-          else
-            []
-          end
-        end
+        signatures = target_method.signatures
 
         # If the method doesn't have any signatures, there's nothing to show
         return if signatures.empty?

lib/ruby_lsp/rubydex/declaration.rb

@@ -108,6 +108,44 @@ class Method
     def to_lsp_completion_kind
       RubyLsp::Constant::CompletionItemKind::METHOD
     end
+
+    # All signatures collected across every definition (re-opens, RBS overloads, alias targets) of this method.
+    #: () -> Array[Rubydex::Signature]
+    def signatures
+      definitions.flat_map do |defn|
+        case defn
+        when Rubydex::MethodDefinition, Rubydex::MethodAliasDefinition
+          defn.signatures
+        else
+          []
+        end
+      end
+    end
+
+    # Decorated parameter list of the first signature, e.g. `(a, b = <default>, &block)`. Returns `()` when there are
+    # no signatures (e.g. an unresolved alias).
+    #: () -> String
+    def decorated_parameters
+      first = signatures.first
+      return "()" unless first
+
+      "(#{first.format})"
+    end
+
+    # Suffix line that hints at additional overloads beyond the first signature, matching the legacy index entry
+    # rendering used in hover.
+    #: () -> String
+    def formatted_signatures
+      count = signatures.size
+      case count
+      when 0, 1
+        ""
+      when 2
+        "\n(+1 overload)"
+      else
+        "\n(+#{count - 1} overloads)"
+      end
+    end
   end
 
   class InstanceVariable

test/requests/hover_expectations_test.rb

@@ -806,19 +806,28 @@ def baz
   end
 
   def test_hover_for_methods_shows_overload_count
-    skip("[RUBYDEX] Temporarily skipped because we don't yet index RBS methods")
+    rbs = <<~RBS
+      class Foo
+        def try_convert: (Object object) -> String?
+                       | (String s) -> String
+                       | (Symbol s) -> String
+      end
+    RBS
+    rbs_uri = URI::Generic.from_path(path: "/fake/path/foo.rbs").to_s
 
     source = <<~RUBY
-      String.try_convert
+      Foo.new.try_convert
     RUBY
 
     with_server(source) do |server, uri|
-      index = server.instance_variable_get(:@global_state).index
-      RubyIndexer::RBSIndexer.new(index).index_ruby_core
+      graph = server.global_state.graph
+      graph.index_source(rbs_uri, rbs, "rbs")
+      graph.resolve
+
       server.process_message(
         id: 1,
         method: "textDocument/hover",
-        params: { textDocument: { uri: uri }, position: { character: 8, line: 0 } },
+        params: { textDocument: { uri: uri }, position: { character: 12, line: 0 } },
       )
 
       contents = server.pop_response.response.contents.value
@@ -905,6 +914,8 @@ def baz
   end
 
   def test_hover_for_aliased_methods
+    skip("[RUBYDEX] need to expose method alias targets in the Ruby API")
+
     source = <<~RUBY
       class Parent
         # Original