[R-pkg-devel] R feature suggestion: Duplicated function arguments check

Not sure if this is the best place to post this message, as it is more of a
suggestion than a question.

When an R function accepts more than a handful of arguments there is the
risk that users accidentally provide arguments twice, e.g myfun(A=1, B=2,
C=4, D=5, A=7), and if those two values are not the same it can have
frustrating side-effects. To catch this I am planning to add a check for
duplicated arguments, as shown below, in one of my own functions. I am now
wondering whether this would be a useful feature for R itself to operate in
the background when running any R function that has more than a certain
number of input arguments.

Cheers, Vincent

myfun = function(...) {
   #check input arguments for duplicate assignments
   input = list(...)
   if (length(input) > 0) {
     argNames = names(input)
     dupArgNames = duplicated(argNames)
     if (any(dupArgNames)) {
       for (dupi in unique(argNames[dupArgNames])) {
         dupArgValues = input[which(argNames %in% dupi)]
         if (all(dupArgValues == dupArgValues[[1]])) { # double arguments,
but no confusion about what value should be
           warning(paste0("\nArgument ", dupi, " has been provided more than
once in the same call, which is ambiguous. Please fix."))
         } else { # double arguments, and confusion about what value should
be,
           stop(paste0("\nArgument ", dupi, " has been provided more than
once in the same call, which is ambiguous. Please fix."))
         }
       }
     }
   }
   # rest of code...
}