Withr - Run Code 'With' Modified State

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A set of functions to run code 'with' safely and temporarily modified global state.

Many of these functions were originally a part of the devtools package, this provides a simple package with limited dependencies to provide access to these functions.

There is also a with_() function to construct new with_* functions if needed.

dir.create("test")
#> Warning in dir.create("test"): 'test' already exists
getwd()
#> [1] "/tmp/RtmpaPrDI5"
with_dir("test", getwd())
#> [1] "/tmp/RtmpaPrDI5/test"
getwd()
#> [1] "/tmp/RtmpaPrDI5"
unlink("test")

Sys.getenv("HADLEY")
#> [1] ""
with_envvar(c("HADLEY" = 2), Sys.getenv("HADLEY"))
#> [1] "2"
Sys.getenv("HADLEY")
#> [1] ""

with_envvar(c("A" = 1),
  with_envvar(c("A" = 2), action = "suffix", Sys.getenv("A"))
)
#> [1] "1 2"

See Also