conditionz: control how many times conditions are thrown

  Scott Chamberlain APRIL 24, 2019

conditionz is a new (just on CRAN today) R package for controlling how many times conditions are thrown.

This package arises from an annoyance in another set of packages I maintain: The brranching package uses the taxize package internally, calling it’s function taxize::tax_name(). The taxize::tax_name() function throws useful messages to the user if their API key is not found, and gives them instructions on how to find it. However, the user does not have to get an API key. If they don’t they then get subjected to lots of repeats of the same message.

I wondered if there’s anything that could be done about this. That is, if the same message is going to be thrown that was already thrown within a function call, just skip additional messages that are the same. (The tibble package has something like this, but as part of the package itself AFAICT)

The package has the following API:

  • ConditionKeeper
  • handle_conditions()
  • handle_messages()
  • handle_warnings()

Exported but mostly meant for internal use:

  • capture_message()
  • capture_warning()


Links:


Installation

Install from CRAN

install.packages("conditionz")

Development version

remotes::install_github("ropenscilabs/conditionz")

Load conditionz

library(conditionz)


ConditionKeeper

ConditionKeeper is an R6 class that keeps track of conditions and lets us determine if conditions have been encountered, how many times they’ve been encountered, etc.

x <- ConditionKeeper$new(times = 4)
x
#> ConditionKeeper
#>  id: ea812b48-5137-4d1b-827a-ae79f59f0ad2
#>  times: 4
#>  messages: 0
x$get_id()
#> [1] "ea812b48-5137-4d1b-827a-ae79f59f0ad2"
x$add("one")
x$add("two")
x
#> ConditionKeeper
#>  id: ea812b48-5137-4d1b-827a-ae79f59f0ad2
#>  times: 4
#>  messages: 2
#>   one  two
x$thrown_already("one")
#> [1] TRUE
x$thrown_already("bears")
#> [1] FALSE
x$not_thrown_yet("bears")
#> [1] TRUE

x$add("two")
x$add("two")
x$add("two")
x$thrown_times("two")
#> [1] 4
x$thrown_enough("two")
#> [1] TRUE
x$thrown_enough("one")
#> [1] FALSE

ConditionKeeper Usage

A simple function that throws messages

squared <- function(x) {
  stopifnot(is.numeric(x))
  y <- x^2
  if (y > 20) message("woops, > than 20! check your numbers")
  return(y)
}
foo <- function(x) {
  vapply(x, function(z) squared(z), numeric(1))
}
bar <- function(x, times = 1) {
  y <- ConditionKeeper$new(times = times)
  on.exit(y$purge())
  vapply(x, function(z) y$handle_conditions(squared(z)), numeric(1))
}

Running the function normally throws many messages

foo(1:10)
#> woops, > than 20! check your numbers
#> woops, > than 20! check your numbers
#> woops, > than 20! check your numbers
#> woops, > than 20! check your numbers
#> woops, > than 20! check your numbers
#> woops, > than 20! check your numbers
#>  [1]   1   4   9  16  25  36  49  64  81 100

Using in ConditionKeeper allows you to control how many messages are thrown

bar(x = 1:10)
#> woops, > than 20! check your numbers
#>  [1]   1   4   9  16  25  36  49  64  81 100
bar(1:10, times = 3)
#> woops, > than 20! check your numbers
#> 
#> woops, > than 20! check your numbers
#> 
#> woops, > than 20! check your numbers
#>  [1]   1   4   9  16  25  36  49  64  81 100


handle_conditions

The function handle_conditions/handle_warnings/handle_messages use ConditionKeeper internally, and are meant as a simpler, but less flexible alternative.

For now, handle_conditions/handle_warnings/handle_messages only allow throwing the condition 1 time with the times parameter. I hope to fix this so you can choose any number you like.

A small example. Here a function that prints a message with every part of the input vector.

foo <- function(x) {
  for (i in x) message("you gave: ", i)
  return(x)
}

If we call that function with the vector 1:5 we get five messages

foo(1:5)
#> you gave: 1
#> you gave: 2
#> you gave: 3
#> you gave: 4
#> you gave: 5
#> [1] 1 2 3 4 5

If we wrap the foo() function call in handle_conditions we get only one message thrown

handle_conditions(foo(1:5))
#> you gave: 1
#> [1] 1 2 3 4 5

The default for the condition parameter is “message”, and calling handle_messages does the same thing

handle_messages(foo(1:5))
#> you gave: 1
#> [1] 1 2 3 4 5

For warnings, call handle_warnings() or set handle_conditions(..., condition = "warning")


To do

  • I’m expecting use cases that I haven’t accounted for, the so-called unknown unknowns
  • The handle_conditions/handle_warnings/handle_messages need some work to be able to actually have times parameter work as advertised
  • I’ll use this package in the brranching package soon, so it will get a real world test


Get in touch

Get in touch if you have any conditionz questions in the issue tracker or the rOpenSci discussion forum.