Modify methods using Pry::Method#redefine

I considered calling redefine source=, but Pry::Method objects are not
designed to be mutable.

lib/pry/commands/edit.rb

@@ -83,7 +83,7 @@ class Pry
         ExceptionPatcher.new(_pry_, state, file_and_line_for_current_exception).perform_patch
       else
         if code_object.is_a?(Pry::Method)
-          Method::Patcher.new(code_object).perform_patch
+          code_object.redefine Pry::Editor.edit_tempfile_with_content(code_object.source)
         else
           raise NotImplementedError, "Cannot yet patch #{code_object} objects!"
         end

lib/pry/method.rb

@@ -270,6 +270,12 @@ class Pry
                   end
     end
 
+    # Update the live copy of the method's source.
+    def redefine(source)
+      Patcher.new(self).patch_in_ram source
+      Pry::Method(owner.instance_method(name))
+    end
+
     # Can we get the source code for this method?
     # @return [Boolean]
     def source?

lib/pry/method/patcher.rb

@@ -14,30 +14,25 @@ class Pry
       end
 
       # perform the patch
-      def perform_patch
-        source = patched_code
+      def patch_in_ram(source)
         if method.alias?
           with_method_transaction do
-            cached_eval source
+            redefine source
           end
         else
-          cached_eval source
+          redefine source
         end
       end
 
       private
 
-      def cached_eval(source)
+      def redefine(source)
         @@source_cache[cache_key] = source
-        TOPLEVEL_BINDING.eval source, cache_key
-      end
-
-      def patched_code
-        @patched_code ||= wrap(Pry::Editor.edit_tempfile_with_content(method.source.lines.to_a))
+        TOPLEVEL_BINDING.eval wrap(source), cache_key
       end
 
       def cache_key
-        "pry!#{method.owner.object_id}!#{method.name}"
+        "pry-redefined(0x#{method.owner.object_id.to_s(16)}##{method.name})"
       end
 
       # Run some code ensuring that at the end target#meth_name will not have changed.

spec/method/patcher_spec.rb

@@ -0,0 +1,27 @@
+require 'helper'
+
+describe Pry::Method::Patcher do
+
+  before do
+    @x = Object.new
+    def @x.test; :before; end
+    @method = Pry::Method(@x.method(:test))
+  end
+
+  it "should change the behaviour of the method" do
+    @x.test.should == :before
+    @method.redefine "def @x.test; :after; end\n"
+    @x.test.should == :after
+  end
+
+  it "should return a new method with new source" do
+    @method.source.strip.should == "def @x.test; :before; end"
+    @method.redefine("def @x.test; :after; end\n").
+      source.strip.should == "def @x.test; :after; end"
+  end
+
+  it "should change the source of new Pry::Method objects" do
+    @method.redefine "def @x.test; :after; end\n"
+    Pry::Method(@x.method(:test)).source.strip.should == "def @x.test; :after; end"
+  end
+end