Title: Tools for Defensive Programming
Version: 0.3.1
Description: Tools for defensive programming, inspired by 'purrr' mappers and based on 'rlang'.'attempt' extends and facilitates defensive programming by providing a consistent grammar, and provides a set of easy to use functions for common tests and conditions. 'attempt' only depends on 'rlang', and focuses on speed, so it can be easily integrated in other functions and used in data analysis.
License: MIT + file LICENSE
Encoding: UTF-8
URL: https://github.com/ColinFay/attempt
LazyData: true
Suggests: testthat, knitr, rmarkdown, curl
VignetteBuilder: knitr
Imports: rlang
RoxygenNote: 7.1.0
NeedsCompilation: no
Packaged: 2020-05-03 20:24:38 UTC; colin
Author: Colin Fay ORCID iD [aut, cre]
Maintainer: Colin Fay <contact@colinfay.me>
Repository: CRAN
Date/Publication: 2020-05-03 20:50:02 UTC

attempt package

Description

Tools for defensive programming in R. 'attempt' extends and facilitates defensive programming by providing a consistent grammar, and provides a set of easy to use functions for common tests and conditions. 'attempt' only depends on rlang & withr, and focuses on speed, so it can be easily integrated in other functions and used in data analysis.

Author(s)

colin <contact@colinfay.me>

Attempt

Description

A wrapper around base try that allows you to set a custom message when an error/warning occurs. attempt returns the value if there is no error nor message.

Usage

attempt(expr, msg = NULL, verbose = FALSE, silent = FALSE)

Arguments

expr

the expression to be evaluated

msg

the message to return if an error occurs

verbose

wether or not to return to expression producing the error

silent

wether or not the error should be kept under silence

Examples

## Not run: 
attempt(log("a"), msg = "Nop !")

## End(Not run)

discretly

Description

Prevent a funtion from printing message or warning

Usage

discretly(.f)

discreetly(.f)

Arguments

.f

the function to wrap

Value

an error if any, a warning if any, the result if any

Examples

## Not run: 
discrete_mat <- discretly(matrix)
discrete_mat(1:3, 2)

## End(Not run)

Test for all, any or none

Description

Test for all, any or none

Usage

if_all(.l, .p = isTRUE, .f)

if_any(.l, .p = isTRUE, .f)

if_none(.l, .p = isTRUE, .f)

Arguments

.l

the list to test.

.p

the predicate for testing. Defaut is isTRUE.

.f

a mapper or a function run if .p(.x) is TRUE.

Value

If .p(.x) is TRUE, .f() is run.

Examples

if_all(1:10, ~ .x < 11, ~ return(letters[1:10]))
if_any(1:10, is.numeric, ~ return(letters[1:10]))
if_none(1:10, is.numeric, ~ return(letters[1:10]))

If this, then that

Description

If this, then that

Usage

if_then(.x, .p = isTRUE, .f)

if_not(.x, .p = isTRUE, .f)

if_else(.x, .p = isTRUE, .f, .else)

Arguments

.x

the object to test. If NULL (the default), only .p is evaluated.

.p

the predicate for testing. Defaut is isTRUE.

.f

a mapper or a function run if .p(.x) is TRUE

.else

a mapper or a function run if .p(.x) is not TRUE

Value

Depending on wether or not .p(.x) is TRUE, .f() or .else() is run.

Note

If you want these function to return a value, you need to wrap these values into a mapper / a function. E.g, to return a vector, you'll need to write if_then(1, is.numeric, ~ "Yay").

Examples

a <- if_then(1, is.numeric, ~ "Yay")
a <- if_not(1, is.character, ~ "Yay")
a <- if_else(.x = TRUE, .f = ~ "Yay", .else = ~ "Nay")

Is the element of class "try-error"?

Description

Is the element of class "try-error"?

Usage

is_try_error(.x)

Arguments

.x

the object to test

Value

A logical

Examples

x <- attempt(log("a"), silent = TRUE)
is_try_error(x)

Add a function to be run on error

Description

This function behaves as 'on.exit()', but is run on error, and supports mappers.

Usage

on_error(f)

Arguments

f

a function to call on error

Value

A local error handler.

Examples


y <- function(num){
  on_error(~ write( Sys.time(), "error_log.txt", append = TRUE) )
  log(num)
}

Silently attempt

Description

A wrapper around silently and attempt

Usage

silent_attempt(...)

Arguments

...

the expression to evaluate

Value

an error if any, a warning if any.

Examples

## Not run: 
silent_attempt(warn("nop!"))

## End(Not run)

Silently

Description

silently returns a new function that will returns an error or a warning if any, or else returns nothing.

Usage

silently(.f)

Arguments

.f

the function to silence

Value

an error if any, a warning if any. The result is never returned.

Examples

## Not run: 
silent_log <- silently(log)
silent_log(1)
silent_log("a")

## End(Not run)

Warn if

Description

Friendlier messaging functions.

Usage

stop_if(.x, .p = isTRUE, msg = NULL)

stop_if_any(.l, .p = isTRUE, msg = NULL)

stop_if_all(.l, .p = isTRUE, msg = NULL)

stop_if_none(.l, .p = isTRUE, msg = NULL)

stop_if_not(.x, .p = isTRUE, msg = NULL)

warn_if(.x, .p = isTRUE, msg = NULL)

warn_if_any(.l, .p = isTRUE, msg = NULL)

warn_if_all(.l, .p = isTRUE, msg = NULL)

warn_if_none(.l, .p = isTRUE, msg = NULL)

warn_if_not(.x, .p = isTRUE, msg = NULL)

message_if(.x = NULL, .p = isTRUE, msg = NULL)

message_if_any(.l, .p = isTRUE, msg = NULL)

message_if_all(.l, .p = isTRUE, msg = NULL)

message_if_none(.l, .p = isTRUE, msg = NULL)

message_if_not(.x, .p = isTRUE, msg = NULL)

Arguments

.x

the element to evaluate. It can be a predicate function (i.e a function returning TRUE).

.p

the predicate with the condition to test on .x or .l. Default is isTRUE.

msg

the message to return. If NULL (default), the built-in message is printed.

.l

the list of elements to evaluate

Examples

## Not run: 
x <- 12
stop_if(x, ~ .x > 13)
stop_if_not(x, is.character)

a  <- "this is not numeric"
warn_if(a,  is.character )
warn_if_not(a, is.numeric )
b  <- 20
warn_if(b ,  ~ . > 10 ,
         msg = "Wow, that's a lot of b")
c <- "a"
message_if(c, is.character,
         msg = "You entered a character element")

## End(Not run)

surely

Description

Wrap a function in a try

Usage

surely(.f)

Arguments

.f

the function to wrap

Value

an error if any, a warning if any, the result if any

Examples

## Not run: 
sure_log <- surely(log)
sure_log(1)
sure_log("a")

## End(Not run)

Try Catch

Description

Friendlier try catch functions

Usage

try_catch(expr, .e = NULL, .w = NULL, .f = NULL)

try_catch_df(expr)

map_try_catch(l, fun, .e = NULL, .w = NULL, .f = NULL)

map_try_catch_df(l, fun)

Arguments

expr

for simple try catch, the expression to be evaluated

.e

a one side formula or a function evaluated when an error occurs

.w

a one side formula or a function evaluated when a warning occurs

.f

a one side formula or an expression evaluated before returning or exiting

l

for map_* function, a list of arguments

fun

for map_* function, a function to try with the list l

Details

try_catch handles errors and warnings the way you specify. try_catch_df returns a tibble with the call, the error message if any, the warning message if any, and the value of the evaluated expression.

Examples

## Not run: 
try_catch(log("a"), .e = ~ paste0("There was an error: ", .x))
try_catch(log(1), .f = ~ print("finally"))
try_catch(log(1), .f = function() print("finally"))

## End(Not run)

Manipulate messages and warnings

Description

with_message and with_warning add a warning or a message to a function. without_message and without_warning turn the warning and message off.

Usage

with_message(.f, msg)

with_warning(.f, msg)

without_message(.f)

without_warning(.f)

Arguments

.f

the function to wrap

msg

the message to print

Value

a function

Examples

msg_as_num <- with_message(as.numeric, msg = "Numeric conversion")
warn_as_num <- with_warning(as.numeric, msg = "Numeric conversion")