How to make a function aware of its own call arguments

Are you aware of any function what would query the original function call
arguments no matter what happens in the function?

Use missing() first.
If you can't use missing() first, or use it early in a parent function and pass a flag, you could perhaps pass a copy of the parent function call to the daughter function and see if an argument was included in the call. Example:

f1 <- function(x,  ...) {
	if(missing(x)) x<-3
	f2(x, match.call())
}

f2 <- function(x, f1.call) {
	testx <- if(is.null(f1.call$x)) "x was absent in f1" else "x specified in f1"
	xval <- paste("x now set to", x)
	
	cat(sprintf("%s\n%s\n",testx, xval))
	
}

f1()

f1(x=2)





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