[ruby-core:123491] [Ruby Bug#21641] Hash#to_s behaves different in 3.4

16 Oct 2025

      Issue #21641 has been updated by shan (Shannon Skipper).

Please feel free to join us on [Ruby Discord](https://discord.gg/ad2acQFtkh) or [#ruby IRC](https://web.libera.chat/#ruby) to discuss all the options! Refining Hash is one way:
``` ruby
module LegacyHashToS
  refine Hash do
    def to_s = "{#{map { "#{_1.inspect}=>#{_2.inspect}" }.join(', ')}}"
  end
end

using LegacyHashToS

{x: 1}.to_s
#=> "{:x=>1}"
```

----------------------------------------
Bug #21641: Hash#to_s behaves different in 3.4
https://bugs.ruby-lang.org/issues/21641#change-114863

* Author: matheussilvasantos (Matheus Oliveira)
* Status: Open
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
I couldn't find anywhere documenting this change from Ruby 3.3 to Ruby 3.4:

3.3.9:
``` ruby
...
irb
3.3.9 :001 > {x:1}.to_s
 => "{:x=>1}" 
3.3.9 :002 >

3.4.0:
```ruby
3.4.0 :001 > {x:1}.to_s
 => "{x: 1}" 
3.4.0 :002 > 

Is there a way to continue with the old behaviour - flag to compilation, monkey patch, etc.?

Unfortunately, the application I'm working on stores the `to_s` in Redis and use it later; if the result doesn't match for the same Hash, it would break a few things.

-- 
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