From 2a8a7312032c38cb59125d232f67bfede2c11742 Mon Sep 17 00:00:00 2001
From: Kevin Clark <kclark@apache.org>
Date: Wed, 18 Jun 2008 01:01:07 +0000
Subject: [PATCH] deprecate_class! now sets up a proxy class that logs a
 warning when used

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@668926 13f79535-47bb-0310-9956-ffa450edef68
---
 lib/rb/lib/thrift/deprecation.rb | 41 ++++++++++++++++++++++++++++----
 lib/rb/spec/deprecation_spec.rb  | 29 ++++++++++++++++++++++
 2 files changed, 66 insertions(+), 4 deletions(-)

diff --git a/lib/rb/lib/thrift/deprecation.rb b/lib/rb/lib/thrift/deprecation.rb
index e170f57f..d237ee49 100644
--- a/lib/rb/lib/thrift/deprecation.rb
+++ b/lib/rb/lib/thrift/deprecation.rb
@@ -31,6 +31,42 @@ class Module
   end
 end
 
+module Thrift::DeprecationProxy
+  def self.new(obj)
+    Class.new(obj) do
+      klass = self
+      @@self = klass
+      @@obj = obj
+      instance_methods.sort.reject { |x| [:__id__,:__send__].include? x.to_sym }.each do |sym|
+        undef_method sym
+      end
+      def method_missing(sym, *args, &block)
+        @@obj.instance_method(sym).bind(self).call(*args, &block)
+      end
+      (class << self;self;end).class_eval do
+        @@self = klass
+        @@obj = obj
+        @@warned = false
+        instance_methods.sort.reject { |x| [:__id__,:__send__].include? x.to_sym }.each do |sym|
+          undef_method sym
+        end
+        def method_missing(sym, *args, &block)
+          unless @@warned
+            STDERR.puts "Warning: class #{@@obj.inspect} is deprecated"
+            STDERR.puts "  from #{caller.first}"
+            @@warned = true
+          end
+          if @@self.__id__ == self.__id__
+            @@obj.send sym, *args, &block
+          else
+            @@obj.method(sym).unbind.bind(self).call(*args, &block)
+          end
+        end
+      end
+    end
+  end
+end
+
 module Kernel
   # Provides an alternate name for the class for deprecation purposes
   # Example:
@@ -39,13 +75,10 @@ module Kernel
   # at the moment this only works for creating top-level constants
   # if necessary, this can be extended to take something like :'Thrift::TBinaryProtocol'
   # alternately, Module can be extended with a similar method
-  #
-  # another idea is to not make the old name a pointer to the new, but rather
-  # a pointer to a proxy class that logs deprecation warnings and forwards methods
   def deprecate_class!(klasses)
     return unless Thrift::DEPRECATION
     klasses.each_pair do |old, new|
-      Object.const_set old, new
+      Object.const_set old, Thrift::DeprecationProxy.new(new)
     end
   end
 end
diff --git a/lib/rb/spec/deprecation_spec.rb b/lib/rb/spec/deprecation_spec.rb
index cb462b45..ff10177c 100644
--- a/lib/rb/spec/deprecation_spec.rb
+++ b/lib/rb/spec/deprecation_spec.rb
@@ -168,6 +168,12 @@ end
 describe "deprecate_class!" do
   it_should_behave_like "deprecation"
 
+  def stub_stderr(callstr, offset=1)
+    STDERR.should_receive(:puts).with("Warning: class #{callstr} is deprecated")
+    line = caller.first[/\d+$/].to_i + offset
+    STDERR.should_receive(:puts).with("  from #{__FILE__}:#{line}")
+  end
+
   it "should create a new global constant that points to the old one" do
     begin
       klass = Class.new do
@@ -176,6 +182,7 @@ describe "deprecate_class!" do
         end
       end
       deprecate_class! :DeprecationSpecOldClass => klass
+      stub_stderr(klass)
       ::DeprecationSpecOldClass.should eql(klass)
       ::DeprecationSpecOldClass.new.foo.should == "foo"
     ensure
@@ -194,10 +201,32 @@ describe "deprecate_class!" do
         end
         deprecate_class! :DeprecationSpecOldClass => klass
       end
+      stub_stderr(klass)
       ::DeprecationSpecOldClass.should eql(klass)
       ::DeprecationSpecOldClass.new.foo.should == "foo"
     ensure
       Object.send :remove_const, :DeprecationSpecOldClass if Object.const_defined? :DeprecationSpecOldClass
     end
   end
+
+  it "should not prevent the deprecated class from being a superclass" do
+    begin
+      klass = Class.new do
+        def foo
+          "foo"
+        end
+      end
+      deprecate_class! :DeprecationSpecOldClass => klass
+      subklass = Class.new(::DeprecationSpecOldClass) do
+        def foo
+          "subclass #{super}"
+        end
+      end
+      stub_stderr(klass)
+      subklass.superclass.should eql(klass)
+      subklass.new.foo.should == "subclass foo"
+    ensure
+      Object.send :remove_const, :DeprecationSpecOldClass if Object.const_defined? :DeprecationSpecOldClass
+    end
+  end
 end
-- 
2.17.1