last_warnings {rlang}

Display last messages and warnings

Description

last_warnings() and last_messages() return a list of all warnings and messages that occurred during the last R command.

global_entrace() must be active in order to log the messages and warnings.

By default the warnings and messages are printed with a simplified backtrace, like last_error(). Use summary() to print the conditions with a full backtrace.

Usage

last_warnings(n = NULL)

last_messages(n = NULL)

Arguments

n

How many warnings or messages to display. Defaults to all.

Examples

Enable backtrace capture with global_entrace():

global_entrace()

Signal some warnings in nested functions. The warnings inform about which function emitted a warning but they don't provide information about the call stack:

f <- function() { warning("foo"); g() }
g <- function() { warning("bar", immediate. = TRUE); h() }
h <- function() warning("baz")

f()
#> Warning in g() : bar
#> Warning messages:
#> 1: In f() : foo
#> 2: In h() : baz

Call last_warnings() to see backtraces for each of these warnings:

last_warnings()
#> [[1]]
#> <warning/rlang_warning>
#> Warning in `f()`:
#> foo
#> Backtrace:
#>     x
#>  1. \-global f()
#>
#> [[2]]
#> <warning/rlang_warning>
#> Warning in `g()`:
#> bar
#> Backtrace:
#>     x
#>  1. \-global f()
#>  2.   \-global g()
#>
#> [[3]]
#> <warning/rlang_warning>
#> Warning in `h()`:
#> baz
#> Backtrace:
#>     x
#>  1. \-global f()
#>  2.   \-global g()
#>  3.     \-global h()

This works similarly with messages:

f <- function() { inform("Hey!"); g() }
g <- function() { inform("Hi!"); h() }
h <- function() inform("Hello!")

f()
#> Hey!
#> Hi!
#> Hello!

rlang::last_messages()
#> [[1]]
#> <message/rlang_message>
#> Message:
#> Hey!
#> ---
#> Backtrace:
#>     x
#>  1. \-global f()
#>
#> [[2]]
#> <message/rlang_message>
#> Message:
#> Hi!
#> ---
#> Backtrace:
#>     x
#>  1. \-global f()
#>  2.   \-global g()
#>
#> [[3]]
#> <message/rlang_message>
#> Message:
#> Hello!
#> ---
#> Backtrace:
#>     x
#>  1. \-global f()
#>  2.   \-global g()
#>  3.     \-global h()

See Also

last_error()