Issue #15778 has been updated by st0012 (Stan Lo). I had a chance to chat with multiple people about this proposal, so I want to share what I found here: - From chatting with @maximecb, my understanding is that such feature requires Ruby to keep all the frames on the stack in an accessible format, which will limit the optimisation YJIT could do. This is fine for development, but using it in production with YJIT "might" not be ideal. - Rails would be happy to use such feature to enrich its exception backtrace in log, which will be helpful in development. - In production, in addition to the potential issue with YJIT, more things like data scrubbing needs to be considered. ---------------------------------------- Feature #15778: Expose an API to pry-open the stack frames in Ruby https://bugs.ruby-lang.org/issues/15778#change-101560 * Author: gsamokovarov (Genadi Samokovarov) * Status: Open * Priority: Normal * Assignee: ko1 (Koichi Sasada) ---------------------------------------- Hello, I'm the maintainer of the web-console (https://github.com/rails/web-console/) gem, where one of our features is to jump between the frames in which an error occurred. To accomplish this, I currently use the Debug Inspector CRuby API. I think we should expose this functionality in Rubyland, so tools like web-console don't need to resort to C code for this. This also makes it quite harder for me to support different implementations like JRuby or TruffleRuby as everyone is having a different way to create Ruby Binding objects that represent the frames. Here the API ideas: Add `Thread::Backtrace::Location#binding` method that can create a binding for a specific caller of the current frame. We can reuse the existing `Kernel.caller_locations` method to generate the array of `Thread::Backtrace::Location` objects. We can optionally have the `Kernel.caller_locations(debug: true)` argument if we cannot generate the bindings lazily on the VM that can instruct the VM to do the slower operation. - `Thread::Backtrace::Location#binding` returns `Binding|nil`. Nil result may mean that the current location is a C frame or a JITted/optimized frame and we cannot debug it. We can also expose the DebugInspector API directly, as done in the https://github.com/banister/debug_inspector gem, but for tools like web-console, we'd need to map the bindings with the backtrace, as we cannot generate Bindings for every frame (C frames) and this needs to be done in application code, so I think the `Thread::Backtrace::Location#binding` is the better API for Ruby-land. Such API can help us eventually write most of our debuggers in Ruby as right now we don't have a way to do Post-Mortem debugging without native code or even start our debuggers without monkey-patching `Binding`. I have presented this idea in a RubyKaigi's 2019 talk called "Writing Debuggers in Plain Ruby", you can check-out the slides for more context: http://kaigi-debuggers-in-ruby.herokuapp.com. -- https://bugs.ruby-lang.org/