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Validate and format a function call for use in error messages

Source: R/cnd-abort.R
format_error_call.Rd

  • error_call() takes either a frame environment or a call. If the input is an environment, error_call() acts like frame_call() with some additional logic, e.g. for S3 methods and for frames with a local_error_call().

  • format_error_call() simplifies its input to a simple call (see section below) and formats the result as code (using cli if available). Use this function to generate the "in" part of an error message from a stack frame call.

    format_error_call() first passes its input to error_call() to fetch calls from frame environments.

Usage

format_error_call(call)

error_call(call)

Arguments

call

The execution environment of a currently running function, e.g. caller_env(). The function will be mentioned in error messages as the source of the error. See the call argument of abort() for more information.

Value

Either a string formatted as code or NULL if a simple call could not be generated.

Details of formatting

  • The arguments of function calls are stripped.

  • Complex function calls containing inlined objects return NULL.

  • Calls to if preserve the condition since it might be informative. Branches are dropped.

  • Calls to operators and other special syntax are formatted using their names rather than the potentially confusing function form.

Examples

# Arguments are stripped
writeLines(format_error_call(quote(foo(bar, baz))))
#> `foo()`

# Returns `NULL` with complex calls such as those that contain
# inlined functions
format_error_call(call2(list))
#> NULL

# Operators are formatted using their names rather than in
# function call form
writeLines(format_error_call(quote(1 + 2)))
#> `1 + 2`