debugging code inside %dofuture%

[iagomosqueira]

I have set up a call to browser() inside a foreach loop handled by %dofuture%. When the debugging session opens there I cannot get output on the R terminal. Code uses the sequential plan and has not set up progressr. Is there anything I can do to the std output back?

Running on R 4.3.1 on Linux.

[HenrikBengtsson]

The problem you're experiencing is similar to using browser() or debug() when calling a function with capture.output(). The output produced by browser() and debug() is captured, recorded internally, to be outputted at a later time. See HenrikBengtsson/Wishlist-for-R#90 for an example of this problem. This is also what happens internally when parallelizing using futures.

The solution is to tell the future framework to capture and output at the same time. This can be done by using:

plan(sequential, split = TRUE)

The default is split = FALSE.

See Section 'Interactive debugging' in the blog post 'future 1.20.1 - The Future Just Got a Bit Brighter' on 2020-11-06 for more explanations.

[iagomosqueira]

Perfect, many thanks, sorry I missed that argument.