Feature #21105: Improve Ruby Stack Trace to Include Exact Error Position (Column Number)

• Status: Closed
• Assignee: -
• Target version: -

[ennder (Jérôme BATAILLE)]

Subject

Improve Ruby Stack Trace to Include Exact Error Position (Column Number)

Description

Currently, when an exception occurs in Ruby, the stack trace provides the file name and line number but does not indicate the exact position (column number) where the error occurred within the line. This lack of precision can make debugging more challenging, especially in cases where multiple method calls or expressions are present on the same line.

Example

class Example
  def self.run
    nil.some_method_call  # Error occurs here
  end
end

Example.run

Expected Behavior

The stack trace should include the column number where the error occurred, e.g.:

trace.rb:4:10:in `run': undefined method `some_method_call' for nil:NilClass (NoMethodError)

Benefits

More precise debugging.

Easier identification of errors in complex one-liner expressions.

Better tooling support for editors and debuggers.

Additional Notes

Would it be possible to add this enhancement in a future Ruby version?

Thank you for considering this request!

[ennder (Jérôme BATAILLE)]

• Description updated (diff)

[ennder (Jérôme BATAILLE)]

• Description updated (diff)

[Eregon (Benoit Daloze)]

It is already shown:

class Example
  def self.run
    nil.foo.bar.baz
  end
end

Example.run

example.rb:3:in `run': undefined method `foo' for nil (NoMethodError)

    nil.foo.bar.baz
       ^^^^
	from example.rb:7:in `<main>'

Adding columns would add a lot of noise and would not be clearer than that.
So I think we can close this as "already done, just in a different/clearer way"

[matz (Yukihiro Matsumoto)]

• Status changed from Open to Closed

I like introducing the column number in the error message, but in reality, it is hard to get column numbers from the error object, and I don't think it's worth the extensive overhaul to make that possible.
Probably we will add this in the future wishlist.

Matz.

[mame (Yusuke Endoh)]

I think it is worth to display column info as trace.rb:3:7: in 'run': ... . When you click on it in the vscode terminal, it will open the file and jumpto that location.

However, there are numerous problems to making this happen.

• Which specific column position should be displayed: For NoMethodError, near the beginning of the method name seems appropriate. However, for ArgumentError, you may want to indicate the position of the argument that caused the problem. Appropriate column locations would change on a node-by-node and exception-by-exception basis.
• Overhead: Currently, the interpreter bytecode only holds the node IDs, not the column information. We need to store column information for each bytecode instruction, which will require memory overhead, or, to reopen and reparse the source file to restore column information each time a backtrace is generated, which will require performance overhead.
• Compatibility: There are a small number of projects that parse backtrace strings using regular expressions. The addition of column numbers will cause that parsing to stop working.

[ennder (Jérôme BATAILLE)]

Sorry to comment on a closed issue.

As a complement, I find it very useful when there is multiple objects calling the same method for exemple :

class Example
  def self.runnable?
    check_one.same_method_call? && check_two.same_method_call?
  end
end

Example.runnable?

# The position in the line helps to know which object is nil
trace.rb:4:46:in `runnable?': undefined method `same_method_call?' for nil:NilClass (NoMethodError)