From: "byroot (Jean Boussier) via ruby-core" <ruby-core@...>
Date: 2023-06-20T14:55:35+00:00
Subject: [ruby-core:113955] [Ruby master Bug#19739] Key cannot be found in a Hash when slice! method is applied to the key

Issue #19739 has been updated by byroot (Jean Boussier).





That is very interesting.



The two strings are identical (aside from one being frozen):



```ruby

require "objspace"



hash = {}

key = "ABC O�"

p key.hash

key.slice!(/ o�$/i) 



p key.hash

puts ObjectSpace.dump(key)

hash[key] = true

p "#{key} in #{hash}: value is #{hash[key].inspect}"

puts ObjectSpace.dump(hash.keys.first)

p [hash.keys.first, key, hash.keys.first == key]

p [hash.keys.first.hash, key.hash]

```



```

1883393806954673666

-2878200511277543492

{"address":"0x10129f048", "type":"STRING", "class":"0x1011c2418", "embedded":true, "bytesize":3, "encoding":"UTF-8", "memsize":40, "flags":{"wb_protected":true}}

"ABC in {\"ABC\"=>true}: value is nil"

{"address":"0x10129ebc0", "type":"STRING", "class":"0x1011c2418", "frozen":true, "embedded":true, "fstring":true, "bytesize":3, "value":"ABC", "encoding":"UTF-8", "memsize":40, "flags":{"wb_protected":true}}

["ABC", "ABC", true]

[-2878200511277543491, -2878200511277543491]

```



The hash code is the same, and `==` returns true.



I had a quick look at recent changes in `String#slice!` that could explain why it's fixed in 3.2, but didn't spot anything yet.



What is interesting though is that the first access to `key.hash` returns `-2878200511277543492`, but then later it consistently returns `-2878200511277543491`. I wonder if there is an off by one bug somewhere.



----------------------------------------

Bug #19739: Key cannot be found in a Hash when slice! method is applied to the key

https://bugs.ruby-lang.org/issues/19739#change-103610



* Author: ilya.andreyuk (Ilya Andreyuk)

* Status: Open

* Priority: Normal

* ruby -v: 3.1.4

* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN

----------------------------------------

Hello,

Key cannot be found in a Hash when slice! method is applied to the key. I cannot reproduce this behaviour with sub! or gsub! methods:



``` ruby

hash = {}

key = "ABC O�"

key.slice!(/ o�$/i) 

# key.sub!(/ o�$/i, '')

# key.gsub!(/ o�$/i, '')

hash[key] = true

"#{key} in #{hash}: value is #{hash[key]}"



=> "ABC in {\"ABC\"=>true}: value is "

```



Also it seems that ruby 2.7.6 and 3.2.2 don't have this issue.







-- 

https://bugs.ruby-lang.org/

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