From: "ko1 (Koichi Sasada) via ruby-core" <ruby-core@...>
Date: 2023-03-10T05:42:50+00:00
Subject: [ruby-core:112822] [Ruby master Feature#19452] `Thread::Backtrace::Location` should have column information if possible.

Issue #19452 has been updated by ko1 (Koichi Sasada).


Let me clear why column information is better than `node_id`

My understanding:

* Better than `node_id`
  * B1. We can get one column information (maybe most wider information, for example: `a.b.c.d.func(...)` for `func()`.
  * B2. We can get (maybe) corresponding node by column information. not exact same with `node_id` but similar.
  * B3. Column information is not magical than `node_id`
  * B4. Can detect file modification on reparsing (not all modification though) because we can not get corresponding node by column information.
* Worse than `node_id`
  * W1. More memory consumption
  * W2. Can not get exact corresponding node with column information because some nodes can have same column information.
  * W3. Can not get corresponding node on reparsing when the script was modified, even if spacing or commenting (<=> B4)
  * W4. (personal concern) if we introduce it, I'm afraid that people ask to hold more and more information than the column information
* Both worse
  * S1. Need to reparse a script and analyze the script to get more information like method name, parameters and so on.



----------------------------------------
Feature #19452: `Thread::Backtrace::Location` should have column information if possible.
https://bugs.ruby-lang.org/issues/19452#change-102329

* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
I discussed this with @mame and it would be pretty useful if we could also get the column information from exception backtrace location, even if it was slow.

A POC:

```ruby
class Thread::Backtrace::Location
  if defined?(RubyVM::AbstractSyntaxTree)
    def first_column
      RubyVM::AbstractSyntaxTree.of(self, keep_script_lines: true).first_column
    end
  else
    def first_column
      raise NotImplementedError
    end
  end
end
```

It would be good to have a standard interface, so we follow the same interface as https://bugs.ruby-lang.org/issues/19451 and vice versa where it makes sense. I'll investigate it.



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