Assigning inside expect_condition() does not work

[torockel]

Hi testthat team,
It seems like assigning does not work inside expect_condition() but does work inside expect_message() and expect_warning():

library(testthat)
foo_message <- function() {
  message("a message")
  5
}

expect_message(a <- foo_message())
a
#> [1] 5

expect_condition(b <- foo_message())
b
#> Error in eval(expr, envir, enclos): object 'b' not found


foo_warning <- function() {
  warning("a warning")
  5
}

expect_warning(c <- foo_warning())
c
#> [1] 5

expect_condition(d <- foo_warning())
d
#> Error in eval(expr, envir, enclos): object 'd' not found

^{Created on 2020-03-26 by the reprex package (v0.3.0)}

I don’t know, if this difference is intended. However, I find it sometimes useful to do stuff like this, which is inspired by the examples of expect_message:

expect_warning(c <- foo_warning())
expect_equal(c, 5)

^{Created on 2020-03-26 by the reprex package (v0.3.0)}

[hadley]

Hmmm, I'm not sure that the current behaviour is wrong. Note that the problem isn't actually assignment:

library(testthat)
a <- 1
expect_condition(a <- 2, NA)
a
#> [1] 2

^{Created on 2020-04-13 by the reprex package (v0.3.0)}

It's that expect_condition() stops running any code after it captures the first condition. expect_message() and expect_warning() work differently as they capture all messages and warnings so evaluate all code.

[torockel]

Thank you for your explanation. My expectation of the function expect_condition() was wrong. Lead by your very interesting book (https://adv-r.hadley.nz/conditions.html), I thought expect_condition() was a more general form of expect_message(), expect_warning() and expect_error()). So, I came to the (wrong) conclusion that it would behave like these functions. However, it seems to be behave different to all three. Even expect_error() does not stop after a message, which I first expected after reading your reply and because expect_error() and expect_condition() are documented together:

library(testthat)

foo_message <- function() {
  message("a message")
  5
}

expect_error(d <- foo_message(), NA)
#> a message
d
#> [1] 5

^{Created on 2020-04-17 by the reprex package (v0.3.0)}

I seem to be not the only one, who misunderstood expect_condition() (#972). Maybe just add the sentence you wrote in your reply (“expect_condition() stops running any code after it captures the first condition.”) to the documentation of expect_condition()?

[hadley]

I've changed my mind: this isn't a documentation problem, it's a bug that's worth fixing.