[ruby-core:121360] [Ruby Misc#20968] `Array#fetch_values` unexpected method name in stack trace

["mame (Yusuke Endoh) via ruby-core" <ruby-core@ml.ruby-lang.org>]

Issue #20968 has been updated by mame (Yusuke Endoh).


So now Method#call can directly invoke a block?
No, it's just the stack trace deceiving you by hiding crucial details.

At the dev meeting, @ko1 also raised this issue. He suggested that, for this reason, we should stop writing in Ruby and revert to C. However, I expect @k0kubun to oppose this change due to YJIT’s performance benefits.

The root of the problem lies in the distinction between different types of function calls: standard C function calls do not appear in the Ruby backtrace, whereas calls made via `rb_funcall`, etc., do.

I proposed that the Ruby method should maintain this distinction: normal method calls should not appear in the backtrace, and if a Ruby method is invoked explicitly using `Primitive.rb_funcall` or something, it should be included in the backtrace.
However, a decision on my proposal was postponed until we could confirm whether there are sufficient real-world cases where naive hiding would cause issues.

In any case, it was reaffirmed that matz strongly prefers that `<internal:` not be displayed. Given this, implementation costs and some runtime overhead are considered acceptable. If no one else takes it on, I will implement it myself (probably after RubyKaigi).

----------------------------------------
Misc #20968: `Array#fetch_values` unexpected method name in stack trace
https://bugs.ruby-lang.org/issues/20968#change-112331

* 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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