From: "Eregon (Benoit Daloze) via ruby-core" <ruby-core@...>
Date: 2025-12-16T08:42:00+00:00
Subject: [ruby-core:124225] [Ruby Bug#21783] {Method,UnboundMethod,Proc}#source_location returns columns in bytes and not in characters

Issue #21783 has been updated by Eregon (Benoit Daloze).


matz (Yukihiro Matsumoto) wrote in #note-8:
> I'd like to cancel `source_location` to have column information in 4.0, due to this concern.
> 
> Matz.

Thank you for the quick reply, I think that would be the worst outcome though, https://bugs.ruby-lang.org/issues/6012 was already opened 14 years ago and I have seen multiple users needing this in the last years.
It is one of the features I'm most looking forward to in Ruby 4.0 (in fact it's one of two features that really interests me in 4.0: that and Ractor improvements, the rest looks rather unexciting to me).
IOW, I would much rather have byte columns in 4.0 than no columns at all.

If we delay this, we'll implicitly tell people that using RubyVM::AbstractSyntaxTree is the only way to get column information, and that's bad because it only works on CRuby and it's not a proper API.
Alternative Ruby implementations might have to define their own API to get column information, vs just using the one we have agreed on in #6012 (I'd much rather not get there).

> In my personal opinion, I am leaning toward byte index, though.

Let's go with byte columns then? I can make a PR to document that.
It seems you and @kddnewton agree on that, and I'm basically hesitating which is best, but definitely better byte columns than columns.
I see it has already been reverted though :/ https://github.com/ruby/ruby/commit/065c48cdf11a1c4cece84db44ed8624d294f8fd5

----------------------------------------
Bug #21783: {Method,UnboundMethod,Proc}#source_location returns columns in bytes and not in characters
https://bugs.ruby-lang.org/issues/21783#change-115711

* Author: Eregon (Benoit Daloze)
* Status: Open
* ruby -v: ruby 4.0.0dev (2025-12-14T07:11:02Z master 711d14992e) +PRISM [x86_64-linux]
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
The documentation says:
```
= Proc.source_location

(from ruby core)
------------------------------------------------------------------------
  prc.source_location  -> [String, Integer, Integer, Integer, Integer]

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

Returns the location where the Proc was defined. The returned Array
contains:
  (1) the Ruby source filename
  (2) the line number where the definition starts
  (3) the column number where the definition starts
  (4) the line number where the definition ends
  (5) the column number where the definitions ends

This method will return nil if the Proc was not defined in Ruby (i.e.
native).
```

So it talks about column numbers, so it should be a number of characters and not of bytes.

But currently it's a number of bytes:
```
$ ruby --parser=prism -ve 'def �t�; end; p method(:�t�).source_location'
ruby 4.0.0dev (2025-12-14T07:11:02Z master 711d14992e) +PRISM [x86_64-linux]
["-e", 1, 0, 1, 14]

$ ruby --parser=parse.y -ve 'def �t�; end; p method(:�t�).source_location'
ruby 4.0.0dev (2025-12-14T07:11:02Z master 711d14992e) [x86_64-linux]
["-e", 1, 0, 1, 14]
```

The last number should be 12 because `"def �t�; end".size` is 12 characters.

This is a Ruby-level API so I would never expect "byte columns" here, I think it's clear it should be a number of "editor columns" i.e. a number of characters.



-- 
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