Evaluate and Capture Conditions

eval_capture_conditions()

Evaluates an expression while also capturing error and warning conditions. Function always returns a named list list(result=, warning=, error=). If there are no errors or warnings, those elements will be NULL. If there is an error, the result element will be NULL.

Messages are neither saved nor printed to the console.

Evaluation is done via rlang::eval_tidy(). If errors and warnings are produced using the {cli} package, the messages are processed with cli::ansi_strip() to remove styling from the message.

captured_condition_as_message()/captured_condition_as_error()

These functions take the result from eval_capture_conditions() and return errors or warnings as either messages (via cli::cli_inform()) or errors (via cli::cli_abort()). These functions handle cases where the condition messages may include curly brackets, which would typically cause issues when processed with the cli::cli_*() functions.

Functions return the "result" from eval_capture_conditions().

Usage

eval_capture_conditions(expr, data = NULL, env = caller_env())

captured_condition_as_message(
  x,
  message = c("The following {type} occured:", x = "{condition}"),
  type = c("error", "warning"),
  envir = rlang::current_env()
)

captured_condition_as_error(
  x,
  message = c("The following {type} occured:", x = "{condition}"),
  type = c("error", "warning"),
  call = get_cli_abort_call(),
  envir = rlang::current_env()
)

Arguments

expr

An expression or quosure to evaluate.

data

A data frame, or named list or vector. Alternatively, a data mask created with as_data_mask() or new_data_mask(). Objects in data have priority over those in env. See the section about data masking.

env

The environment in which to evaluate expr. This environment is not applicable for quosures because they have their own environments.

x

(captured_condition)
a captured condition created by eval_capture_conditions().

message

(character)
message passed to cli::cli_inform() or cli::cli_abort(). The condition being printed is saved in an object named condition, which should be included in this message surrounded by curly brackets.

type

(string)
the type of condition to return. Must be one of 'error' or 'warning'.

envir

Environment to evaluate the glue expressions in.

call

(environment)
Execution environment of currently running function. Default is get_cli_abort_call().

Value

a named list

Examples

# function executes without error or warning
eval_capture_conditions(letters[1:2])
#> $result
#> [1] "a" "b"
#> 
#> $warning
#> NULL
#> 
#> $error
#> NULL
#> 
#> attr(,"class")
#> [1] "captured_condition" "list"              

# an error is thrown
res <- eval_capture_conditions(stop("Example Error!"))
res
#> $result
#> NULL
#> 
#> $warning
#> NULL
#> 
#> $error
#> [1] "Example Error!"
#> 
#> attr(,"class")
#> [1] "captured_condition" "list"              
captured_condition_as_message(res)
#> The following error occured:
#> ✖ Example Error!
#> NULL

# if more than one warning is returned, all are saved
eval_capture_conditions({
  warning("Warning 1")
  warning("Warning 2")
  letters[1:2]
})
#> $result
#> [1] "a" "b"
#> 
#> $warning
#> [1] "Warning 1" "Warning 2"
#> 
#> $error
#> NULL
#> 
#> attr(,"class")
#> [1] "captured_condition" "list"              

# messages are not printed to the console
eval_capture_conditions({
  message("A message!")
  letters[1:2]
})
#> $result
#> [1] "a" "b"
#> 
#> $warning
#> NULL
#> 
#> $error
#> NULL
#> 
#> attr(,"class")
#> [1] "captured_condition" "list"