Handling errors before warnings in tryCatch

Question

I am dealing with a function that is throwing both errors and warnings. (related: A Warning About Warning )

Often, a warning will proceed an error. In thes

Answer 1

I would write a function that executes an expression and prioritizes the errors.

prioritize.errors <- local({
    # this function executes an expression and stores the warnings 
    # until it finishes executing.
    warnings <- list()
    w.handler <- function(w) {
        warnings <<- c(warnings, list(w))
        invokeRestart('muffleWarning') # here's the trick
    }
    function(expr) {
        withCallingHandlers({expr}, warning=w.handler)
        for (w in warnings) warning(w)
        warnings <<- list()
    }
})

F.warning <- function() {
    warning("a warning")
    message('ok')
}


test <- function(expr) {
    tryCatch(expr, 
        error=function(e) cat("ERROR CAUGHT"), 
        warning=function(w) cat("WARNING CAUGHT")
    )
}

test(prioritize.errors(F.error()))
# ERROR CAUGHT 

test(prioritize.errors(F.warning()))
# ok
# WARNING CAUGHT

test(prioritize.errors(F.errorAndWarning()))
# I have moved on.ERROR CAUGHT