Avoid showing private methods for external references

lib/ruby_lsp/listeners/completion.rb

@@ -440,8 +440,11 @@ def complete_methods(node, name)
         return unless range
 
         guessed_type = type.is_a?(TypeInferrer::GuessedType) && type.name
+        external_references = @node_context.fully_qualified_name != type.name
 
         @index.method_completion_candidates(method_name, type.name).each do |entry|
+          next if entry.visibility == RubyIndexer::Entry::Visibility::PRIVATE && external_references
+
           entry_name = entry.name
           owner_name = entry.owner&.name
 

test/requests/completion_test.rb

@@ -1497,6 +1497,42 @@ def test_guessed_type_name_is_only_included_for_guessed_types
     end
   end
 
+  def test_completion_for_private_methods
+    source = +<<~RUBY
+      class Foo
+        def bar
+          b
+        end
+
+        private
+
+        def baz
+        end
+      end
+
+      foo = Foo.new
+      foo.b
+    RUBY
+
+    with_server(source) do |server, uri|
+      server.process_message(id: 1, method: "textDocument/completion", params: {
+        textDocument: { uri: uri },
+        position: { line: 2, character: 5 },
+      })
+
+      result = server.pop_response.response
+      assert_includes(result.map(&:label), "baz")
+
+      server.process_message(id: 1, method: "textDocument/completion", params: {
+        textDocument: { uri: uri },
+        position: { line: 12, character: 5 },
+      })
+
+      result = server.pop_response.response
+      refute_includes(result.map(&:label), "baz")
+    end
+  end
+
   private
 
   def with_file_structure(server, &block)