Capture Arbitrary Conditions with `withCallingHandlers`

Question

The Problem

I\'m trying to write a function that will evaluate code and store the results, including any possible conditions signaled in the code. I\'ve got this

Answer 1

I think what you're looking for is to use withRestarts when your special condition is signaled, like from warning:

    withRestarts({
        .Internal(.signalCondition(cond, message, call))
        .Internal(.dfltWarn(message, call))
    }, muffleWarning = function() NULL)

so

evalcapt <- function(expr) {
  conds <- list()
  withCallingHandlers(
    val <- eval(expr),
    custom=function(e) {
      message("Caught condition of class ", deparse(class(e)))
      conds <<- c(conds, list(e))
      invokeRestart("muffleCustom")
  } )
  list(val=val, conditions=conds)
}

expr <- expression(withRestarts({
    signalCondition(myCondition)
}, muffleCustom=function() NULL), 25)

leads to

> tryCatch(evalcapt(expr))   
Caught condition of class c("custom", "simpleCondition", "condition")
$val
[1] 25

$conditions
$conditions[[1]]



> tryCatch(
+   evalcapt(expr),               
+   custom=function(e) stop("Hijacked `evalcapt`!")  
+ )
Caught condition of class c("custom", "simpleCondition", "condition")
$val
[1] 25

$conditions
$conditions[[1]]