Index global variables (#2656)

* feat: handle global variable in RBSIndexer

* style: use super short syntax and oneline signature

* style: remove unnecessary initialize declaration in GlobalVariable

lib/ruby_indexer/lib/ruby_indexer/entry.rb

@@ -529,6 +529,9 @@ def initialize(target, unresolved_alias, encoding)
       end
     end
 
+    # Represents a global variable e.g.: $DEBUG
+    class GlobalVariable < Entry; end
+
     # Represents an instance variable e.g.: @a = 1
     class InstanceVariable < Entry
       sig { returns(T.nilable(Entry::Namespace)) }

lib/ruby_indexer/lib/ruby_indexer/rbs_indexer.rb

@@ -44,6 +44,8 @@ def process_declaration(declaration, pathname)
       when RBS::AST::Declarations::Constant
         namespace_nesting = declaration.name.namespace.path.map(&:to_s)
         handle_constant(declaration, namespace_nesting, pathname.to_s)
+      when RBS::AST::Declarations::Global
+        handle_global_variable(declaration, pathname)
       else # rubocop:disable Style/EmptyElse
         # Other kinds not yet handled
       end
@@ -271,6 +273,23 @@ def handle_constant(declaration, nesting, file_path)
       ))
     end
 
+    sig { params(declaration: RBS::AST::Declarations::Global, pathname: Pathname).void }
+    def handle_global_variable(declaration, pathname)
+      name = declaration.name.to_s
+      file_path = pathname.to_s
+      location = to_ruby_indexer_location(declaration.location)
+      comments = comments_to_string(declaration)
+      encoding = @index.configuration.encoding
+
+      @index.add(Entry::GlobalVariable.new(
+        name,
+        file_path,
+        location,
+        comments,
+        encoding,
+      ))
+    end
+
     sig { params(member: RBS::AST::Members::Alias, owner_entry: Entry::Namespace).void }
     def handle_signature_alias(member, owner_entry)
       file_path = member.location.buffer.name
@@ -294,6 +313,7 @@ def handle_signature_alias(member, owner_entry)
         RBS::AST::Declarations::Class,
         RBS::AST::Declarations::Module,
         RBS::AST::Declarations::Constant,
+        RBS::AST::Declarations::Global,
         RBS::AST::Members::MethodDefinition,
         RBS::AST::Members::Alias,
       )).returns(T.nilable(String))

lib/ruby_indexer/test/rbs_indexer_test.rb

@@ -76,6 +76,20 @@ def test_index_methods
       assert_operator(entry.location.end_column, :>, 0)
     end
 
+    def test_index_global_declaration
+      entries = @index["$DEBUG"]
+      refute_nil(entries)
+      assert_equal(1, entries.length)
+
+      entry = entries.first
+
+      assert_instance_of(Entry::GlobalVariable, entry)
+      assert_equal("$DEBUG", entry.name)
+      assert_match(%r{/gems/rbs-.*/core/global_variables.rbs}, entry.file_path)
+      assert_operator(entry.location.start_column, :<, entry.location.end_column)
+      assert_equal(entry.location.start_line, entry.location.end_line)
+    end
+
     def test_attaches_correct_owner_to_singleton_methods
       entries = @index["basename"]
       refute_nil(entries)