tryStack {berryFunctions}R Documentation

try an expression, returning the error stack

Description

As in try, the result of an expression if it works. If it fails, execution is not halted, but an invisible try-error class object is returned and (unless silent=TRUE) a message catted to the console.
Unlike try, tryStack also returns the calling stack to trace errors and warnings and ease debugging.

Usage

tryStack(
  expr,
  silent = FALSE,
  warn = TRUE,
  short = TRUE,
  file = "",
  removetry = TRUE,
  skip = NULL
)

Arguments

expr

Expression to try, potentially wrapped in curly braces if spanning several commands.

silent

Logical: Should printing of error message + stack be suppressed? Does not affect warnings and messages. DEFAULT: FALSE

warn

Logical: trace warnings and messages also? They are still handled like regular warnings / messages unless file !="", when they are catted into that file. DEFAULT: TRUE

short

Logical: should trace be abbreviated to upper -> middle -> lower? If NA, it is set to TRUE for warnings and messages, FALSE for errors. DEFAULT: TRUE

file

File name passed to cat. If given, Errors will be appended to the file after two empty lines. if warn=T and file!="", warnings and messages will not be shown, but also appended to the file. This is useful in lapply simulation runs. DEFAULT: "" (catted to the console)

removetry

Logical: should all stack entries matching typical tryCatch expressions be removed? Unless the call contains customized tryCatch code, this can be left to the DEFAULT: TRUE

skip

Character string(s) to be removed from the stack. e.g. "eval(expr, p)". Use short=F to find exact matches. DEFAULT: NULL

Value

Value of expr if evaluated successfully. If not, an invisible object of class "try-error" as in try with the stack in object[2]. For nested tryStack calls, object[3], object[4] etc. will contain "– empty error stack –"

Author(s)

Berry Boessenkool, berry-b@gmx.de, Nov 2016

See Also

try, traceCall, https://r.789695.n4.nabble.com/Stack-trace-td4021537.html, https://stackoverflow.com/questions/15282471/get-stack-trace-on-trycatched-error-in-r, https://stackoverflow.com/questions/1975110/printing-stack-trace-and-continuing-after-error-occurs-in-r, https://stackoverflow.com/questions/16879821/save-traceback-on-error-using-trycatch

Examples


# Functions -----

lower <- function(a) {message("fake message, a = ", a); a+10}
middle <- function(b) {plot(b, main=b) ; warning("fake warning, b = ", b); lower(b) }
upper <- function(c) {cat("printing c:", c, "\n") ; middle(c)}
d <- upper(42)
d
rm(d)


# Classical error management with try -----

is.error( d <- upper("42"), TRUE, TRUE) # error, no d creation
traceback()                     # calling stack, but only in interactive mode

d <- try(upper("42"), silent=TRUE)      # d created
cat(d)                                  # with error message, but no traceback
inherits(d, "try-error")                # use for coding


# way cooler with tryStack -----

d <- tryStack(upper("42") ) # like try, but with traceback, even for warnings
cat(d)
d <- tryStack(upper("42"), silent=TRUE, warn=0) # don't trace warnings
d <- tryStack(upper("42"), short=FALSE)

tryStack(upper(42)) # returns normal output, but warnings are easier to debug
# Note: you can also set options(showWarnCalls=TRUE)

stopifnot(inherits(d, "try-error"))
stopifnot(tryStack(upper(42))==52)

## Not run:  ## file writing not wanted by CRAN checks
d <- tryStack(upper("42"), silent=TRUE, file="log.txt")
openFile("log.txt")
unlink("log.txt")

## End(Not run)

op <- options(warn=2)
d <- try(upper("42") )
cat(d)
d <- tryStack(upper("42") )
d <- tryStack(upper("42"), warn=FALSE)
cat(d)
options(op) ; rm(op)

# Nested calls -----

f <- function(k) tryStack(upper(k), silent=TRUE)
d <- f(42)                 ; cat("-----\n", d, "\n-----\n") ; rm(d)
d <- f("42")               ; cat("-----\n", d, "\n-----\n") ; rm(d)
d <- tryStack(f(4) )       ; cat("-----\n", d, "\n-----\n") ; rm(d)
# warnings in nested calls are printed twice, unless warn=0
d <- tryStack(f(4), warn=0) # could also be set within 'f'

d <- tryStack(f("4"))      ; cat("-----\n", d, "\n-----\n")
d[1:3] ; rm(d)
# empty stack at begin - because of tryStack in f, no real error happened in f


# Other tests -----

cat( tryStack(upper("42")) )
f <- function(k) tryStack(stop("oh oh"))
d <- f(42) ; cat("-----\n", d, "\n-----\n") ; rm(d) # level 4 not helpful, but OK

# stuff with base::try
f <- function(k) try(upper(k), silent=TRUE)
d <- f(42)     ; cat("-----\n", d, "\n-----\n") ; rm(d)
d <- f("42")   ; cat("-----\n", d, "\n-----\n") ; rm(d) # regular try output

f2 <- function(k) tryStack(f(k), warn=0, silent=TRUE)
d <- f2(42)    ; cat("-----\n", d, "\n-----\n") ; rm(d)
d <- f2("42")  ; cat("-----\n", d, "\n-----\n") ; rm(d) # try -> no error.
# -> Use tryCatch and you can nest those calls. note that d gets longer.



[Package berryFunctions version 1.20.1 Index]