More effectively determine method ownership for RBI generation

lib/tapioca/gem/listeners/methods.rb

@@ -66,7 +66,7 @@ def compile_directly_owned_methods(tree, module_name, mod, for_visibility = [:pu
         end
         def compile_method(tree, symbol_name, constant, method, visibility = RBI::Public.new)
           return unless method
-          return unless method.owner == constant
+          return unless method_owned_by_constant?(method, constant)
           return if @pipeline.symbol_in_payload?(symbol_name) && !@pipeline.method_in_gem?(method)
 
           signature = signature_of(method)
@@ -142,6 +142,29 @@ def compile_method(tree, symbol_name, constant, method, visibility = RBI::Public
           tree << rbi_method
         end
 
+        # Check whether the method is defined by the constant.
+        #
+        # In most cases, it works to check that the constant is the method owner. However,
+        # in the case that a method is also defined in a module prepended to the constant, it
+        # will be owned by the prepended module, not the constant.
+        #
+        # This method implements a better way of checking whether a constant defines a method.
+        # It walks up the ancestor tree via the `super_method` method; if any of the super
+        # methods are owned by the constant, it means that the constant declares the method.
+        sig { params(method: UnboundMethod, constant: Module).returns(T::Boolean) }
+        def method_owned_by_constant?(method, constant)
+          # Widen the type of `method` to be nilable
+          method = T.let(method, T.nilable(UnboundMethod))
+
+          while method
+            return true if method.owner == constant
+
+            method = method.super_method
+          end
+
+          false
+        end
+
         sig { params(mod: Module).returns(T::Hash[Symbol, T::Array[Symbol]]) }
         def method_names_by_visibility(mod)
           {

spec/tapioca/gem/pipeline_spec.rb

@@ -1210,6 +1210,64 @@ class Bar; end
       assert_equal(output, compile)
     end
 
+    it "compiles method that is also prepended" do
+      add_ruby_file("foo.rb", <<~RUBY)
+        module Foo
+          def bar
+            super
+          end
+        end
+
+        class Baz
+          prepend Foo
+
+          def bar; end
+        end
+      RUBY
+
+      output = template(<<~RBI)
+        class Baz
+          include ::Foo
+
+          def bar; end
+        end
+
+        module Foo
+          def bar; end
+        end
+      RBI
+
+      assert_equal(output, compile)
+    end
+
+    it "compiles a method that is prepended without calling super" do
+      add_ruby_file("foo.rb", <<~RUBY)
+        module Foo
+          def bar; end
+        end
+
+        class Baz
+          prepend Foo
+
+          def bar; end
+        end
+      RUBY
+
+      output = template(<<~RBI)
+        class Baz
+          include ::Foo
+
+          def bar; end
+        end
+
+        module Foo
+          def bar; end
+        end
+      RBI
+
+      assert_equal(output, compile)
+    end
+
     it "ignores methods on other objects" do
       add_ruby_file("bar.rb", <<~RUBY)
         class Bar