Use alias_method for invalid names

This allows using the same code for both "specially named" and regular
methods. This uses :__delegate as the name, which may be visible to
users in backtraces for these methods.

Co-authored-by: Luke Gruber <luke.gruber@shopify.com>

Author: jhawthorn

lib/delegate.rb

@@ -400,14 +400,29 @@ def DelegateClass(superclass, &block)
   public_instance_methods = superclass.public_instance_methods
   public_instance_methods -= ignores
 
-  normal, special = public_instance_methods.partition { |m| m.match?(/\A[a-zA-Z]\w*[!\?]?\z/) }
+  methods_to_define =
+    public_instance_methods.map{|x| [x, true] } +
+    protected_instance_methods.map{|x| [x, false] }
 
-  source = normal.map do |method|
-    "def #{method}(...); __getobj__.#{method}(...); end"
-  end
+  source = []
+
+  methods_to_define.each do |target_name, is_protected|
+    unless target_name.match?(/\A[a-zA-Z]\w*[!\?]?\z/)
+      placeholder_name = :__delegate
+    end
 
-  protected_instance_methods.each do |method|
-    source << "def #{method}(...); __getobj__.__send__(#{method.inspect}, ...); end"
+    send_source =
+      if is_protected || placeholder_name
+        "__getobj__.__send__(#{target_name.inspect}, ...)"
+      else
+        "__getobj__.#{target_name}(...)"
+      end
+    source << "def #{placeholder_name || target_name}(...); #{send_source}; end"
+
+    if placeholder_name
+      source << "alias_method #{target_name.inspect}, :#{placeholder_name}"
+      source << "remove_method :#{placeholder_name}"
+    end
   end
 
   klass.module_eval do
@@ -426,10 +441,6 @@ def __setobj__(obj)  # :nodoc:
 
     class_eval(source.join(";"), __FILE__, __LINE__)
 
-    special.each do |method|
-      define_method(method, Delegator.delegating_block(method))
-    end
-
     protected(*protected_instance_methods)
   end
 

test/test_delegate.rb

@@ -170,6 +170,22 @@ def test_call_visibiltiy
     assert_raise(NoMethodError) { obj.__send__(:parent_private) }
   end
 
+  class ClassWithInvalidName
+    define_method(:" ") { :space }
+    define_method(:"\t") { :tab }
+    protected :"\t"
+  end
+
+  def test_delegateclass_invalid_name
+    delegate = DelegateClass(ClassWithInvalidName)
+    instance = delegate.new(ClassWithInvalidName.new)
+    assert_equal :space, instance.send(:" ")
+    assert_equal :space, instance.__send__(:" ")
+
+    assert_equal :tab, instance.send(:"\t")
+    assert_equal :tab, instance.__send__(:"\t")
+  end
+
   class IV < DelegateClass(Integer)
     attr_accessor :var