[ruby/ostruct] Add access to public instance methods in case they are overriden

lib/ostruct.rb

@@ -62,8 +62,7 @@
 #   first_pet                 # => #<OpenStruct name="Rowdy">
 #   first_pet == second_pet   # => true
 #
-#
-# == Implementation
+# == Caveats
 #
 # An OpenStruct utilizes Ruby's method lookup structure to find and define the
 # necessary methods for properties. This is accomplished through the methods
@@ -72,10 +71,41 @@
 # This should be a consideration if there is a concern about the performance of
 # the objects that are created, as there is much more overhead in the setting
 # of these properties compared to using a Hash or a Struct.
+# Creating an open struct from a small Hash and accessing a few of the
+# entries can be 200 times slower than accessing the hash directly.
+#
+# This may also be the source of incompatibilities between Ruby versions:
+#
+#   o = OpenStruct.new
+#   o.then # => nil in Ruby < 2.6, enumerator for Ruby >= 2.6
+#
+# Builtin methods may be overwritten this way, which may be a source of bugs
+# or security issues:
+#
+#   o = OpenStruct.new
+#   o.methods # => [:to_h, :marshal_load, :marshal_dump, :each_pair, ...
+#   o.methods = [:foo, :bar]
+#   o.methods # => [:foo, :bar]
+#
+# To help remedy clashes, OpenStruct uses only protected/private methods ending with `!`
+# and defines aliases for builtin public methods by adding a `!`:
+#
+#   o = OpenStruct.new(make: 'Bentley', class: :luxury)
+#   o.class # => :luxury
+#   o.class! # => OpenStruct
+#
+# It is recommended (but not enforced) to not use fields ending in `!`.
+#
+# For all these reasons, consider not using OpenStruct at all.
 #
 class OpenStruct
   VERSION = "0.2.0"
 
+  instance_methods.each do |method|
+    new_name = "#{method}!"
+    alias_method new_name, method
+  end
+
   #
   # Creates a new OpenStruct object.  By default, the resulting OpenStruct
   # object will have no attributes.

test/ostruct/test_ostruct.rb

@@ -241,4 +241,9 @@ class TC_OpenStruct < Test::Unit::TestCase
     assert_equal(:foo, os.method)
     assert_equal(:bar, os.class)
   end
+
+  def test_access_original_methods
+    os = OpenStruct.new(method: :foo)
+    assert_equal(os.object_id, os.method!(:object_id).call)
+  end
 end