From: "wanabe (_ wanabe) via ruby-core" <ruby-core@...>
Date: 2026-08-16T04:33:02+00:00
Subject: [ruby-core:126399] [Ruby Bug#19910] Set#delete_if behavior inconsistent with Array/Hash

Issue #19910 has been updated by wanabe (_ wanabe).

Status changed from Open to Closed

This behavior was fixed by e4f85bfc311a3812de7bc2e9d068934e8b364574 == https://bugs.ruby-lang.org/issues/21216.

```
$ git checkout e4f85bfc311a3812de7bc2e9d068934e8b364574~ && make -j miniruby > /de
v/null && ./miniruby -I$(git rev-parse --show-toplevel)/lib a.rb
Previous HEAD position was e4f85bfc311 Implement Set as a core class
HEAD is now at b1283b45e62 maybe fix bindgen
[1, 3, 5, 6, 7]
{1 => 1, 3 => 3, 5 => 5, 6 => 6, 7 => 7}
#<Set: {0, 1, 2, 3, 4, 5, 6, 7}>

$ git checkout e4f85bfc311a3812de7bc2e9d068934e8b364574 && make -j miniruby > /dev
/null && ./miniruby -I$(git rev-parse --show-toplevel)/lib a.rb
Previous HEAD position was b1283b45e62 maybe fix bindgen
HEAD is now at e4f85bfc311 Implement Set as a core class
[1, 3, 5, 6, 7]
{1 => 1, 3 => 3, 5 => 5, 6 => 6, 7 => 7}
#<Set: {1, 3, 5, 6, 7}>
```

----------------------------------------
Bug #19910: Set#delete_if behavior inconsistent with Array/Hash
https://bugs.ruby-lang.org/issues/19910#change-118537

* Author: segiddins (Samuel Giddins)
* Status: Closed
* ruby -v: 3.2.2
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
Given the following script:

```ruby
#!/usr/bin/env ruby

require 'set'

def enum(collection)
  i = 0
  collection.delete_if do
    i += 1
    raise ArgumentError if i == 6
    i.odd?
  end
rescue ArgumentError
  return collection
end

pp enum([0, 1, 2, 3, 4, 5, 6, 7])
pp enum([0, 1, 2, 3, 4, 5, 6, 7].to_h { [_1, _1] })
pp enum([0, 1, 2, 3, 4, 5, 6, 7].to_set)
```

It results in:

```
[1, 3, 5, 6, 7]
{1=>1, 3=>3, 5=>5, 6=>6, 7=>7}
#<Set: {0, 1, 2, 3, 4, 5, 6, 7}>
```

As you can see, when an exception is raise inside `delete_if` on Hash/Array, the already-considered elements are still removed from the array. For `Set`, no elements are deleted (due to the implementation that builds up an intermediary list of elements to delete, then removes them from the underlying hash afterwards). It would be very helpful if `Set#delete_if` behaved consistently with other core collection types



-- 
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