When trying to access a character on a string buffer object via `:[]`, if the object being accessed currently returns `html_safe?` as true,

we used to set  `@html_safe` variable as true on new object created. When doing something like

x = 'Hello'.html_safe
x[/a/, 1]

would throw an error on ruby 2.2, since when nothign gets matched nil is returned by the code and it tries to set   `@html_safe` value to true,
which would error since starting 2.2 nil is frozen.

This change adds a safety net to avoid setting `@html_safe = true` on frozen objects.

Fixes #18235

1 files changed, 9 insertions, 0 deletions

diff --git a/activesupport/test/safe_buffer_test.rb b/activesupport/test/safe_buffer_test.rb
index efa9d5e61f..fca4b45276 100644
--- a/activesupport/test/safe_buffer_test.rb
+++ b/activesupport/test/safe_buffer_test.rb
@@ -165,4 +165,13 @@ class SafeBufferTest < ActiveSupport::TestCase
     x = 'foo %{x} bar'.html_safe % { x: 'qux' }
     assert x.html_safe?, 'should be safe'
   end
+
+  test 'Should not affect frozen objects when accessing characters' do
+    x = 'Hello'.html_safe
+    assert_nothing_raised do
+      x[/a/, 1]
+    end
+  end
+
+
 end