improve traceback in remote errors

[mtmorgan]

• do not report traceback 'above' the user-provided FUN in bplapply
• closes #245

[mtmorgan]

@MikeDMorgan could you see if this addresses (mostly) your concern?

BiocManager::install("Bioconductor/BiocParallel", ref = "issue-245")

My simple example gives me

g = function() stop("stopping in 'g'")
f = function(i) { if (i == 2) g(); i }
result <- bptry(bplapply(1:4, f, BPPARAM = SerialParam()))

and then

> attr(result[[2]], "traceback") |> cat(sep = "\n")
6: handle_error(e)
5: h(simpleError(msg, call))
4: .handleSimpleError(function (e)
   {
       annotated_condition <- handle_error(e)
       stop(annotated_condition)
   }, "stopping in 'g'", base::quote(g()))
3: stop("stopping in 'g'") at #1
2: g() at #1
1: FUN(...)

where the interesting stuff is frames 1, 2, and 3 (so trimming 45+ calls...) and extends 'into' the tryCatch; currently 4, 5, and 6 are not relevant, but I'm not sure how to robustly mask them... The call stack is also presented in the same way as traceback(), whereas before it was reversed.

[MikeDMorgan]

Hi @mtmorgan - I can now get the full callstack down to Rcpp - thank you for implemeting this so quickly. I'll consider #245 resolved.