[ruby-core:102960] [Ruby master Bug#17735] `Hash#transform_keys!` drops non evaluated keys

[nobu@ruby-lang.org]

Issue #17735 has been updated by nobu (Nobuyoshi Nakada).


These are just a bug, not a spec.

```ruby
  ruby_version_is ""..."2.5.1" do
    it "partially modifies the contents if we broke from the block" do
      @hash.transform_keys! do |v|
        break if v == :c
        v.succ
      end
      @hash.should == { c: 1, d: 4 }
    end
  end

  ruby_version_is "2.5.1" do
    it "returns the processed keys if we broke from the block" do
      @hash.transform_keys! do |v|
        break if v == :c
        v.succ
      end
      @hash.should == { b: 1, c: 2 }
    end
  end
```

----------------------------------------
Bug #17735: `Hash#transform_keys!` drops non evaluated keys
https://bugs.ruby-lang.org/issues/17735#change-91023

* Author: kachick (Kenichi Kamiya)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-darwin20]
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
```ruby
hash = {a: 1, b: 2, c: 3}
hash.transform_values!(){ raise } rescue
p hash #=> {:a=>1, :b=>2, :c=>3}
```

```ruby
hash = {a: 1, b: 2, c: 3}
hash.transform_keys!(){ raise } rescue
p hash #=> {}
```

Is this an intentional behavior?
I expected behavior like `transform_values!` in `transform_keys!` (Keeping non evaluated key-value pairs when exiting the block).

PR: https://github.com/ruby/ruby/pull/4294



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