Merge pull request #32 from lionel-/impl-helpers-list

Export helpers list

NAMESPACE

@@ -18,6 +18,7 @@ export(starts_with)
 export(vars_pull)
 export(vars_rename)
 export(vars_select)
+export(vars_select_helpers)
 export(with_vars)
 import(rlang)
 importFrom(Rcpp,cppFunction)

NEWS.md

@@ -80,6 +80,10 @@ vars_select(names(mtcars), .data$cyl : .data$drat)
 * `has_vars()` is a predicate that tests whether a variable context
   has been set (#21).
 
+* The selection helpers are now exported in a list
+  `vars_select_helpers`.  This is intended for APIs that embed the
+  helpers in the evaluation environment.
+
 
 ## Fixes
 

R/select-helpers.R

@@ -145,3 +145,41 @@ grep_vars <- function(needle, haystack, ...) {
 which_vars <- function(needle, haystack) {
   which(needle == haystack)
 }
+
+
+#' List of selection helpers
+#'
+#' This list contains all selection helpers exported in tidyselect. It
+#' is useful when you want to embed the helpers in your API without
+#' having to track addition of new helpers in tidyselect.
+#'
+#' @export
+#' @examples
+#' # You can easily embed the helpers by burying them in the scopes of
+#' # input quosures. For this example we need an environment where
+#' # tidyselect is not attached:
+#' local(envir = baseenv(), {
+#'   vars <- c("foo", "bar", "baz")
+#'   helpers <- tidyselect::vars_select_helpers
+#'
+#'   my_select <- function(...) {
+#'     quos <- rlang::quos(...)
+#'     quos <- lapply(quos, rlang::env_bury, !!! helpers)
+#'
+#'     tidyselect::vars_select(vars, !!! quos)
+#'   }
+#'
+#'   # The user can now call my_select() with helpers without having
+#'   # to attach tidyselect:
+#'   my_select(starts_with("b"))
+#' })
+vars_select_helpers <- list(
+  starts_with = starts_with,
+  ends_with = ends_with,
+  contains = contains,
+  matches = matches,
+  num_range = num_range,
+  one_of = one_of,
+  everything = everything,
+  last_col = last_col
+)

R/vars-pull.R

@@ -63,3 +63,12 @@ vars_pull <- function(vars, var = -1) {
 
   vars[[pos]]
 }
+
+# FIXME: Workaround rlang bug
+is_integerish <- function(x, n = NULL) {
+  if (typeof(x) == "integer") return(TRUE)
+  if (typeof(x) != "double") return(FALSE)
+  if (!is.finite(x)) return(FALSE)
+  if (!is_null(n) && length(x) != n) return(FALSE)
+  all(x == as.integer(x))
+}