Merge pull request #20737 from gouravtiwari/multibyte_chars_slice_fix

Fixed multibyte-chars slice! behavior to return nil for out-of-bound
parameters

3 files changed, 23 insertions, 2 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index c02c5a82f5..e5d945bb42 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,8 @@
+*   Update `ActiveSupport::Multibyte::Chars#slice!` to return `nil` if the
+    arguments are out of bounds, to mirror the behavior of `String#slice!`
+
+    *Gourav Tiwari*
+
 *   Fix `number_to_human` so that 999999999 rounds to "1 Billion" instead of
     "1000 Million".
 
diff --git a/activesupport/lib/active_support/multibyte/chars.rb b/activesupport/lib/active_support/multibyte/chars.rb
index f6a2e7e949..707cf200b5 100644
--- a/activesupport/lib/active_support/multibyte/chars.rb
+++ b/activesupport/lib/active_support/multibyte/chars.rb
@@ -86,7 +86,8 @@ module ActiveSupport #:nodoc:
       end
 
       # Works like <tt>String#slice!</tt>, but returns an instance of
-      # Chars, or nil if the string was not modified.
+      # Chars, or nil if the string was not modified. The string will not be
+      # modified if the range given is out of bounds
       #
       #   string = 'Welcome'
       #   string.mb_chars.slice!(3)    # => #<ActiveSupport::Multibyte::Chars:0x000000038109b8 @wrapped_string="c">
@@ -94,7 +95,10 @@ module ActiveSupport #:nodoc:
       #   string.mb_chars.slice!(0..3) # => #<ActiveSupport::Multibyte::Chars:0x00000002eb80a0 @wrapped_string="Welo">
       #   string # => 'me'
       def slice!(*args)
-        chars(@wrapped_string.slice!(*args))
+        string_sliced = @wrapped_string.slice!(*args)
+        if string_sliced
+          chars(string_sliced)
+        end
       end
 
       # Reverses all characters in the string.
diff --git a/activesupport/test/multibyte_chars_test.rb b/activesupport/test/multibyte_chars_test.rb
index e1c4b705f8..8d4d9d736c 100644
--- a/activesupport/test/multibyte_chars_test.rb
+++ b/activesupport/test/multibyte_chars_test.rb
@@ -413,12 +413,24 @@ class MultibyteCharsUTF8BehaviourTest < ActiveSupport::TestCase
     assert_equal 'にち', @chars.slice!(1..2)
   end
 
+  def test_slice_bang_returns_nil_on_out_of_bound_arguments
+    assert_equal nil, @chars.mb_chars.slice!(9..10)
+  end
+
   def test_slice_bang_removes_the_slice_from_the_receiver
     chars = 'úüù'.mb_chars
     chars.slice!(0,2)
     assert_equal 'ù', chars
   end
 
+  def test_slice_bang_returns_nil_and_does_not_modify_receiver_if_out_of_bounds
+    string = 'úüù'
+    chars = string.mb_chars
+    assert_nil chars.slice!(4, 5)
+    assert_equal 'úüù', chars
+    assert_equal 'úüù', string
+  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) }