R .call argument in stop function -

what use of .call argument in stop function?

the page (?stop) explains "call. logical, indicating if call should become part of error message.".

could 1 explain .call argument intuitive example?

thanks

just try yourself:

f = function () stop('foo')  g = function () stop('bar', call. = false)  f() # error in f(): foo g() # error: bar 

… , compare output. that’s difference.

the use of argument when want hide irrelevant detail end user otherwise drown out actual error message or actively misleading.

for instance, i have package contains following functions¹:

#' @export import = function (module, ...) {     # … code here …     module_path = find_module(module)     # … more code here … }  find_module = function (module) {     # … code here …     if (no_module_found)         stop('unable load module ', module, '.', call. = false) } 

now, can see function import exported package, function find_module isn’t. consequently user doesn’t know function, , should not know it: it’s irrelevant implementation detail. if hadn’t specified call. = false in stop above, error message have contained reference hidden function, have confused user of package.

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¹ that’s small lie, code different; earlier version of package did contain code.