From: "Dan0042 (Daniel DeLorme) via ruby-core" <ruby-core@...>
Date: 2025-04-08T17:34:21+00:00
Subject: [ruby-core:121593] [Ruby Misc#20968] `Array#fetch_values` unexpected method name in stack trace

Issue #20968 has been updated by Dan0042 (Daniel DeLorme).


> In any case, it was reaffirmed that matz strongly prefers that `<internal:` not be displayed.

I somewhat agree that showing "internal" makes it look like we're leaking internal implementation details, but then what about this:

        <array>:211:in 'Array#fetch': index 42 outside of array bounds: -1...1 (IndexError)
        from <array>:211:in 'block in Array#fetch_values'
        from <array>:211:in 'Array#map!'
        from <array>:211:in 'Array#fetch_values'
        from -e:1:in '<main>'

Already such a simple cosmetic change is enough to improve the appearance of the backtrace imho.

----------------------------------------
Misc #20968: `Array#fetch_values` unexpected method name in stack trace
https://bugs.ruby-lang.org/issues/20968#change-112646

* Author: koic (Koichi ITO)
* Status: Open
----------------------------------------

It seems that the current Ruby implementation is displaying unexpected method name in stack trace.

## Expected

Similar to `Hash#fetch_values`, the method name `Array#fetch_values` is expected to be displayed in the stack trace.

```console
$ ruby -e '{k: 42}.fetch_values(:unknown)'
-e:1:in 'Hash#fetch_values': key not found: :unknown (KeyError)
        from -e:1:in '<main>'

$ ruby -e '[1].fetch_values(42)'
-e:1:in 'Array#fetch_values': index 42 outside of array bounds: -1...1 (IndexError)
        from -e:1:in '<main>'
```


## Actual

The stack trace displays the `Array#fetch` method, which user is not aware of, along with the `<internal.array>` stack trace.

```console
$ ruby -e '[1].fetch_values(42)'
<internal:array>:211:in 'Array#fetch': index 42 outside of array bounds: -1...1 (IndexError)
        from <internal:array>:211:in 'block in Array#fetch_values'
        from <internal:array>:211:in 'Array#map!'
        from <internal:array>:211:in 'Array#fetch_values'
        from -e:1:in '<main>'
```


It likely requires an approach such as implementing it in C, as suggested in https://github.com/ruby/ruby/pull/11555.



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