[fix r-lib#71] add perl argument to matches()

NEWS.md

@@ -3,6 +3,8 @@
 
 * `vars_select()` ignores vectors with only zeros (#82). 
 
+* `matches()` has new argument `perl` to allow for Perl-like regular expressions (requested by @GegznaV, #71)
+
 # tidyselect 0.2.5
 
 This is a maintenance release for compatibility with rlang 0.3.0.

R/select-helpers.R

@@ -13,6 +13,7 @@
 #' @param match A string.
 #' @param ignore.case If `TRUE`, the default, ignores case when matching
 #'   names.
+#' @param perl Should Perl-compatible regexps be used?
 #' @param vars,.vars A character vector of variable names. When called
 #'   from inside selecting functions like [dplyr::select()] these are
 #'   automatically set to the names of the table.
@@ -73,10 +74,10 @@ contains <- function(match, ignore.case = TRUE, vars = peek_vars()) {
 
 #' @export
 #' @rdname select_helpers
-matches <- function(match, ignore.case = TRUE, vars = peek_vars()) {
+matches <- function(match, ignore.case = TRUE, perl = FALSE, vars = peek_vars()) {
   stopifnot(is_string(match), nchar(match) > 0)
 
-  grep_vars(match, vars, ignore.case = ignore.case)
+  grep_vars(match, vars, ignore.case = ignore.case, perl = perl)
 }
 
 #' @export

tests/testthat/test-select-helpers.R

@@ -22,6 +22,7 @@ test_that("matches return integer positions", {
   expect_equal(ends_with("d"),   c(2L, 4L))
   expect_equal(contains("eee"),  5L)
   expect_equal(matches(".b."),   c(1L, 3L, 4L))
+  expect_equal(matches("(?<!a)b", perl = TRUE), c(3L, 4L))
 })
 
 test_that("throws with empty pattern is provided", {