Make Chars#slice! behave more like String#slice! [#1243 state:resolved]

- Chars#slice! now returns the slice instead of itself
- Chars#slice! now removes the slice from itself

Signed-off-by: Pratik Naik <pratiknaik@gmail.com>

activesupport/lib/active_support/multibyte/chars.rb

@@ -344,7 +344,19 @@ def slice(*args)
       end
       alias_method :[], :slice
 
-      # Converts first character in the string to Unicode value
+      # Like <tt>String#slice!</tt>, except instead of byte offsets you specify character offsets.
+      #
+      # Example:
+      #   s = 'こんにちは'
+      #   s.mb_chars.slice!(2..3).to_s #=> "にち"
+      #   s #=> "こんは"
+      def slice!(*args)
+        slice = self[*args]
+        self[*args] = ''
+        slice
+      end
+
+      # Returns the codepoint of the first character in the string.
       #
       # Example:
       #   'こんにちは'.mb_chars.ord #=> 12371
@@ -432,7 +444,7 @@ def tidy_bytes
         chars(self.class.tidy_bytes(@wrapped_string))
       end
 
-      %w(lstrip rstrip strip reverse upcase downcase slice tidy_bytes capitalize).each do |method|
+      %w(lstrip rstrip strip reverse upcase downcase tidy_bytes capitalize).each do |method|
         define_method("#{method}!") do |*args|
           unless args.nil?
             @wrapped_string = send(method, *args).to_s

activesupport/test/multibyte_chars_test.rb

@@ -123,7 +123,6 @@ def test_overridden_bang_methods_return_self
       [:rstrip!, :lstrip!, :strip!, :reverse!, :upcase!, :downcase!, :capitalize!].each do |method|
         assert_equal @chars.object_id, @chars.send(method).object_id
       end
-      assert_equal @chars.object_id, @chars.slice!(1).object_id
     end
 
     def test_overridden_bang_methods_change_wrapped_string
@@ -133,10 +132,6 @@ def test_overridden_bang_methods_change_wrapped_string
         proxy.send(method)
         assert_not_equal original, proxy.to_s
       end
-      proxy = chars('Café')
-      proxy.slice!(3)
-      assert_equal 'é', proxy.to_s
-
       proxy = chars('òu')
       proxy.capitalize!
       assert_equal 'Òu', proxy.to_s
@@ -391,6 +386,15 @@ def test_slice_should_take_character_offsets
     assert_equal nil, @chars.slice(7..6)
   end
 
+  def test_slice_bang_returns_sliced_out_substring
+    assert_equal 'にち', @chars.slice!(1..2)
+  end
+
+  def test_slice_bang_removes_the_slice_from_the_receiver
+    @chars.slice!(1..2)
+    assert_equal 'こわ', @chars
+  end
+
   def test_slice_should_throw_exceptions_on_invalid_arguments
     assert_raise(TypeError) { @chars.slice(2..3, 1) }
     assert_raise(TypeError) { @chars.slice(1, 2..3) }