From: "Eregon (Benoit Daloze) via ruby-core" <ruby-core@...>
Date: 2025-12-16T09:36:24+00:00
Subject: [ruby-core:124228] [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).


byroot (Jean Boussier) wrote in #note-10:
> Maybe I'm totally off, but I expect this data to be used to extract the source code, e.g show a snippet of code in an error message, or something akin to that, hence byte offsets seem actually more convenient? (and performant).

Yes, for that case which might indeed be the most common one, it's more convenient to have the columns in bytes.
And I suspect many of these cases would likely use `Prism` and specifically [Prism.node_for](https://github.com/ruby/prism/pull/3808) to get more information, such as showing the method call to which the block was given, highlight some specific part of the block or method, etc.

----------------------------------------
Bug #21783: {Method,UnboundMethod,Proc}#source_location returns columns in bytes and not in characters
https://bugs.ruby-lang.org/issues/21783#change-115714

* 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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