define [[.stringr_pattern (#569)

Fixes #529

NAMESPACE

@@ -2,6 +2,7 @@
 
 S3method("[",stringr_pattern)
 S3method("[",stringr_view)
+S3method("[[",stringr_pattern)
 S3method(print,stringr_view)
 S3method(type,character)
 S3method(type,default)

NEWS.md

@@ -1,5 +1,8 @@
 # stringr (development version)
 
+* Adds `[[.stringr_pattern` method to go along with existing `[.stringr_pattern` 
+  method (@edward-burn, #569).
+
 * In `str_replace_all()`, a `replacement` function now receives all values in
   a single vector. This radically improves performance at the cost of breaking
   some existing uses (#462).

R/modifiers.R

@@ -227,6 +227,15 @@ type.default <- function(x, error_call = caller_env()) {
   )
 }
 
+#' @export
+`[[.stringr_pattern` <- function(x, i) {
+  structure(
+    NextMethod(),
+    options = attr(x, "options"),
+    class = class(x)
+  )
+}
+
 as_bare_character <- function(x, call = caller_env()) {
   if (is.character(x) && !is.object(x)) {
     # All OK!

tests/testthat/test-modifiers.R

@@ -36,3 +36,10 @@ test_that("subsetting preserves class and options", {
   x <- regex("a", multiline = TRUE)
   expect_equal(x[], x)
 })
+
+test_that("stringr_pattern methods", {
+  ex <- coll(c("foo", "bar"))
+  expect_true(inherits(ex[1], "stringr_pattern"))
+  expect_true(inherits(ex[[1]], "stringr_pattern"))
+
+})