[ruby/irb] Display and prioritise instance methods in `ls

<module/class>`
(https://github.com/ruby/irb/pull/496)

https://github.com/ruby/irb/commit/e3d21f9329

lib/irb/cmd/ls.rb

@@ -38,21 +38,34 @@ module IRB
 
       def dump_methods(o, klass, obj)
         singleton_class = begin obj.singleton_class; rescue TypeError; nil end
-        maps = class_method_map((singleton_class || klass).ancestors)
+        dumped_mods = Array.new
+        # singleton_class' ancestors should be at the front
+        maps = class_method_map(singleton_class&.ancestors || [], dumped_mods) + class_method_map(klass.ancestors, dumped_mods)
         maps.each do |mod, methods|
           name = mod == singleton_class ? "#{klass}.methods" : "#{mod}#methods"
           o.dump(name, methods)
         end
       end
 
-      def class_method_map(classes)
-        dumped = Array.new
-        classes.reject { |mod| mod >= Object }.map do |mod|
-          methods = mod.public_instance_methods(false).select do |m|
-            dumped.push(m) unless dumped.include?(m)
+      def class_method_map(classes, dumped_mods)
+        dumped_methods = Array.new
+        classes = classes.reject { |mod| mod >= Object }
+        classes.map do |mod|
+          next if dumped_mods.include? mod
+
+          dumped_mods << mod
+
+          methods = mod.public_instance_methods(false).select do |method|
+            if dumped_methods.include? method
+              false
+            else
+              dumped_methods << method
+              true
+            end
           end
+
           [mod, methods]
-        end.reverse
+        end.compact
       end
 
       class Output

test/irb/test_cmd.rb

@@ -672,6 +672,66 @@ module TestIRB
       assert_match(/C.methods:\s+m5\n/m, out)
     end
 
+    def test_ls_class
+      out, err = execute_lines(
+        "module M1\n",
+        "  def m2; end\n",
+        "  def m3; end\n",
+        "end\n",
+
+        "class C1\n",
+        "  def m1; end\n",
+        "  def m2; end\n",
+        "end\n",
+
+        "class C2 < C1\n",
+        "  include M1\n",
+        "  def m3; end\n",
+        "  def m4; end\n",
+        "  def self.m3; end\n",
+        "  def self.m5; end\n",
+        "end\n",
+        "ls C2"
+      )
+
+      assert_empty err
+      assert_match(/C2.methods:\s+m3\s+m5\n/, out)
+      assert_match(/C2#methods:\s+m3\s+m4\n.*M1#methods:\s+m2\n.*C1#methods:\s+m1\n/, out)
+    end
+
+    def test_ls_module
+      out, err = execute_lines(
+        "module M1\n",
+        "  def m1; end\n",
+        "  def m2; end\n",
+        "end\n",
+
+        "module M2\n",
+        "  include M1\n",
+        "  def m1; end\n",
+        "  def m3; end\n",
+        "  def self.m4; end\n",
+        "end\n",
+        "ls M2"
+      )
+
+      assert_empty err
+      assert_match(/M2\.methods:\s+m4\nModule#methods:/, out)
+      assert_match(/M2#methods:\s+m1\s+m3\n.*M1#methods:\s+m2\n/, out)
+    end
+
+    def test_ls_instance
+      out, err = execute_lines(
+        "class Foo; def bar; end; end\n",
+        "ls Foo.new"
+      )
+
+      assert_empty err
+      assert_match(/Foo#methods:\s+bar/, out)
+      # don't duplicate
+      assert_not_match(/Foo#methods:\s+bar\n.*Foo#methods/, out)
+    end
+
     def test_ls_grep
       pend if RUBY_ENGINE == 'truffleruby'
       out, err = execute_lines("ls 42\n")