Catch a condition — catch

This is a small wrapper around tryCatch() that captures any condition signalled while evaluating its argument. It is useful for situations where you expect a specific condition to be signalled, for debugging, and for unit testing.

Usage

catch_cnd(expr, classes = "condition")

Arguments

expr: Expression to be evaluated with a catching condition handler.
classes: A character vector of condition classes to catch. By default, catches all conditions.

Value

A condition if any was signalled, NULL otherwise.

Examples

catch_cnd(10)
#> NULL
catch_cnd(abort("an error"))
#> <error/rlang_error>
#> Error:
#> ! an error
#> ---
#> Backtrace:
#>      ▆
#>   1. └─pkgdown::build_site_github_pages(new_process = FALSE, install = FALSE)
#>   2.   └─pkgdown::build_site(...)
#>   3.     └─pkgdown:::build_site_local(...)
#>   4.       └─pkgdown::build_reference(...)
#>   5.         ├─pkgdown:::unwrap_purrr_error(...)
#>   6.         │ └─base::withCallingHandlers(...)
#>   7.         └─purrr::map(...)
#>   8.           └─purrr:::map_("list", .x, .f, ..., .progress = .progress)
#>   9.             ├─purrr:::with_indexed_errors(...)
#>  10.             │ └─base::withCallingHandlers(...)
#>  11.             ├─purrr:::call_with_cleanup(...)
#>  12.             └─pkgdown (local) .f(.x[[i]], ...)
#>  13.               ├─base::withCallingHandlers(...)
#>  14.               └─pkgdown:::data_reference_topic(...)
#>  15.                 └─pkgdown:::run_examples(...)
#>  16.                   └─pkgdown:::highlight_examples(code, topic, env = env)
#>  17.                     └─downlit::evaluate_and_highlight(...)
#>  18.                       └─evaluate::evaluate(code, child_env(env), new_device = TRUE, output_handler = output_handler)
#>  19.                         ├─base::withRestarts(...)
#>  20.                         │ └─base (local) withRestartList(expr, restarts)
#>  21.                         │   ├─base (local) withOneRestart(withRestartList(expr, restarts[-nr]), restarts[[nr]])
#>  22.                         │   │ └─base (local) doWithOneRestart(return(expr), restart)
#>  23.                         │   └─base (local) withRestartList(expr, restarts[-nr])
#>  24.                         │     └─base (local) withOneRestart(expr, restarts[[1L]])
#>  25.                         │       └─base (local) doWithOneRestart(return(expr), restart)
#>  26.                         ├─evaluate:::with_handlers(...)
#>  27.                         │ ├─base::eval(call)
#>  28.                         │ │ └─base::eval(call)
#>  29.                         │ └─base::withCallingHandlers(...)
#>  30.                         ├─base::withVisible(eval(expr, envir))
#>  31.                         └─base::eval(expr, envir)
#>  32.                           └─base::eval(expr, envir)
catch_cnd(signal("my_condition", message = "a condition"))
#> <my_condition: a condition>