Add go-to-definition for global variables (#2673)

feat: add go-to-definition for global variables

lib/ruby_lsp/listeners/definition.rb

@@ -39,6 +39,7 @@ def initialize(response_builder, global_state, language_id, uri, node_context, d
           :on_block_argument_node_enter,
           :on_constant_read_node_enter,
           :on_constant_path_node_enter,
+          :on_global_variable_read_node_enter,
           :on_instance_variable_read_node_enter,
           :on_instance_variable_write_node_enter,
           :on_instance_variable_and_write_node_enter,
@@ -120,6 +121,25 @@ def on_constant_read_node_enter(node)
         find_in_index(name)
       end
 
+      sig { params(node: Prism::GlobalVariableReadNode).void }
+      def on_global_variable_read_node_enter(node)
+        entries = @index[node.name.to_s]
+
+        return unless entries
+
+        entries.each do |entry|
+          location = entry.location
+
+          @response_builder << Interface::Location.new(
+            uri: URI::Generic.from_path(path: entry.file_path).to_s,
+            range: Interface::Range.new(
+              start: Interface::Position.new(line: location.start_line - 1, character: location.start_column),
+              end: Interface::Position.new(line: location.end_line - 1, character: location.end_column),
+            ),
+          )
+        end
+      end
+
       sig { params(node: Prism::InstanceVariableReadNode).void }
       def on_instance_variable_read_node_enter(node)
         handle_instance_variable_definition(node.name.to_s)

lib/ruby_lsp/requests/definition.rb

@@ -46,6 +46,7 @@ def initialize(document, global_state, position, dispatcher, sorbet_level)
             Prism::ConstantReadNode,
             Prism::ConstantPathNode,
             Prism::BlockArgumentNode,
+            Prism::GlobalVariableReadNode,
             Prism::InstanceVariableReadNode,
             Prism::InstanceVariableAndWriteNode,
             Prism::InstanceVariableOperatorWriteNode,

test/requests/definition_expectations_test.rb

@@ -671,6 +671,27 @@ def baz
     end
   end
 
+  def test_definition_for_global_variables
+    source = <<~RUBY
+      $DEBUG
+    RUBY
+
+    with_server(source) do |server, uri|
+      index = server.instance_variable_get(:@global_state).index
+      RubyIndexer::RBSIndexer.new(index).index_ruby_core
+
+      server.process_message(
+        id: 1,
+        method: "textDocument/definition",
+        params: { textDocument: { uri: uri }, position: { character: 1, line: 0 } },
+      )
+      response = server.pop_response.response.first
+      assert_match(%r{/gems/rbs-.*/core/global_variables.rbs}, response.uri)
+      assert_equal(response.range.start.line, response.range.end.line)
+      assert_operator(response.range.start.character, :<, response.range.end.character)
+    end
+  end
+
   def test_definition_for_instance_variables
     source = <<~RUBY
       class Foo