`No sourcefile available` when debug gem is required inside an eval and breaking into the debugger inside

[u3shit]

Your environment

• ruby -v: ruby 3.1.0p0 (2021-12-25 revision fb4df44d16) [x86_64-linux]
• rdbg -v: rdbg 1.4.0

Describe the bug
I decided to try out the new debug gem bundled with ruby 3.1.0, but it looks like I did too much black magic with how I load my code and it broke. I'm not 100% sure this is valid usage of this gem though, so feel free to close this issue if it is invalid.

To Reproduce
I have two files, a.rb:

require 'debug'
def foo; binding.debugger; end

and b.rb:

eval File.read('a.rb'), binding, 'a.rb'
foo

Running ruby b.rb, I get:

# No sourcefile available for a.rb
=>#0    Object#foo at a.rb:2
  #1    <main> at b.rb:2

If I require debug in b.rb, it works. If I use require_relative 'a' instead of File.read+eval, it works. If I require debug in a separate eval in b.rb, it also works. So does ruby -rdebug b.rb, and rdbg b.rb, obviously.

Expected behavior
It should display the source properly:

[1, 2] in a.rb
     1| require 'debug'
=>   2| def foo; binding.debugger; end

Additional context
Sorry.

[ko1]

Thank you for your report. I'll investigate it.

BTW binding.debugger you only need to use debugger.
(binding.break or binding.b for users prefer to write binding.xxx like binding.pry)

[ko1]

Ah, this is from Ruby 3.1 changes. I'll fix it soon (maybe in Jan).

[jemmaissroff]

I was curious about this so spent a little time investigating.

@ko1 do you think this is happening because the TracePoint.new(:script_compiled) call occurs after the file a.rb has already been loaded? So the debugger can't see the script as it has already been compiled?

Also, as an aside, while investigating this I found TracePoint.trace which looks like a helper method that does both the TracePoint.new and TracePoint.enable calls, and could be used in the :script_compiled case as well as a few other spots in the codebase. Let me know if it would be useful for me to make that PR.

[ko1]

Your investigation is correct. However, if a file name is given for eval method, debugger should try to check the given file name (and if debugger can find a file, debugger should show the existing file). #544 fixes it.