hoistDotArgs.R

hoistDotArgs = function(fn) {
  dotCalls = list()

  findDotArgs = function(exp) {
    if (typeof(exp) == "closure") { # entry point
      expL = as.list(exp)
      args = names(expL)
      if (!("..." %in% args)) return(invisible()) # no dots to hoist
      body = expL[[length(expL)]]
      findDotArgs(body)

    } else if (typeof(exp) == "language") {
      langL = as.list(exp)
      if ("..." %in% langL) {
        # print(exp)
        fnameSym = langL[[1]]
        fnameChar = as.character(fnameSym)
        callee = get(fnameChar) # closure
        args = names(as.list(callee))
        thisCall = list()
        thisCall[[fnameChar]] = args
        dotCalls <<- c(dotCalls, thisCall)
      } else {
        lapply(langL, function (x) {
          findDotArgs(x)
        })
      }
    }
    invisible()
  }

  findDotArgs(fn)
  
  if (length(unique(names(dotCalls))) > 1) {
    print("... passed to more than one different functions; could hoist common args")
  } else {
    dc = dotCalls[[1]]
    fname = names(dotCalls)[[1]]
    args = paste(head(dc, n = length(dc) - 1), collapse = ", ")
    print(sprintf("... passed to %s. Hoist its arguments (%s)", fname, args))
  }

}

given:

priv = function(a2, a3) {
  print(c(a2, a3))
}

priv2 = function(a2, a4) {
  print(c(a2, a4))
}

myfn = function(a1, ...) {
  print(a1)
  priv(...)
}

myfn2 = function(a1, ...) {
  if (a1) {
    priv(...)
  } else {
    priv2(...)
  }
}

then:

> hoistDotArgs(myfn2)
[1] "... passed to more than one different functions; could hoist common args"
> hoistDotArgs(myfn)
[1] "... passed to priv. Hoist its arguments (a2, a3)"