feat: add completion for global variables

lib/ruby_lsp/listeners/completion.rb

@@ -85,6 +85,7 @@ def initialize( # rubocop:disable Metrics/ParameterLists
           :on_constant_path_node_enter,
           :on_constant_read_node_enter,
           :on_call_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,
@@ -180,6 +181,29 @@ def on_call_node_enter(node)
         end
       end
 
+      sig { params(node: Prism::GlobalVariableReadNode).void }
+      def on_global_variable_read_node_enter(node)
+        candidates = @index.prefix_search(node.name.to_s)
+
+        return if candidates.none?
+
+        range = range_from_location(node.location)
+
+        candidates.flatten.each do |entry|
+          entry_name = entry.name
+
+          @response_builder << Interface::CompletionItem.new(
+            label: entry_name,
+            filter_text: entry_name,
+            label_details: Interface::CompletionItemLabelDetails.new(
+              description: entry.file_name,
+            ),
+            text_edit: Interface::TextEdit.new(range: range, new_text: entry_name),
+            kind: Constant::CompletionItemKind::VARIABLE,
+          )
+        end
+      end
+
       sig { params(node: Prism::InstanceVariableReadNode).void }
       def on_instance_variable_read_node_enter(node)
         handle_instance_variable_completion(node.name.to_s, node.location)

lib/ruby_lsp/requests/completion.rb

@@ -17,7 +17,7 @@ class << self
         def provider
           Interface::CompletionOptions.new(
             resolve_provider: true,
-            trigger_characters: ["/", "\"", "'", ":", "@", ".", "=", "<"],
+            trigger_characters: ["/", "\"", "'", ":", "@", ".", "=", "<", "$"],
             completion_item: {
               labelDetailsSupport: true,
             },
@@ -50,6 +50,7 @@ def initialize(document, global_state, params, sorbet_level, dispatcher)
             Prism::CallNode,
             Prism::ConstantReadNode,
             Prism::ConstantPathNode,
+            Prism::GlobalVariableReadNode,
             Prism::InstanceVariableReadNode,
             Prism::InstanceVariableAndWriteNode,
             Prism::InstanceVariableOperatorWriteNode,

test/requests/completion_test.rb

@@ -1431,6 +1431,34 @@ def test_guessed_type_name_is_only_included_for_guessed_types
     end
   end
 
+  def test_completion_for_global_variables
+    source = <<~RUBY
+      $
+      $LOAD
+    RUBY
+
+    with_server(source) do |server, uri|
+      index = server.instance_variable_get(:@global_state).index
+      RubyIndexer::RBSIndexer.new(index).index_ruby_core
+
+      server.process_message(id: 1, method: "textDocument/completion", params: {
+        textDocument: { uri: uri },
+        position: { line: 0, character: 1 },
+      })
+      items = server.pop_response.response
+      assert_operator(items.size, :>, 40)
+
+      server.process_message(id: 1, method: "textDocument/completion", params: {
+        textDocument: { uri: uri },
+        position: { line: 1, character: 1 },
+      })
+      items = server.pop_response.response
+      assert_operator(items.size, :>=, 2)
+      assert_includes(items.map(&:label), "$LOADED_FEATURES")
+      assert_includes(items.map(&:label), "$LOAD_PATH")
+    end
+  end
+
   private
 
   def with_file_structure(server, &block)