make detect helpers honor regex "|" operator (#340)

* make detect helpers honor regex "|" operator

* update for hadley

Author: carlganz

NEWS.md

@@ -1,5 +1,7 @@
 # stringr (development version)
 
+* Update `str_starts()` and `str_ends()` functions so they honor regex operator precedence. (@carlganz)
+
 * `word()` now returns all the sentence when using a negative `start` parameter
   that is greater or equal than the number of words. (@pdelboca, #245)
 

R/detect.r

@@ -82,7 +82,7 @@ str_starts <- function(string, pattern, negate = FALSE) {
     fixed = stri_startswith_fixed(string, pattern, negate = negate, opts_fixed = opts(pattern)),
     coll  = stri_startswith_coll(string,  pattern, negate = negate, opts_collator = opts(pattern)),
     regex = {
-      pattern2 <- paste0("^", pattern)
+      pattern2 <- paste0("^(", pattern, ")")
       attributes(pattern2) <- attributes(pattern)
       str_detect(string, pattern2, negate)
     }
@@ -98,7 +98,7 @@ str_ends <- function(string, pattern, negate = FALSE) {
          fixed = stri_endswith_fixed(string, pattern, negate = negate, opts_fixed = opts(pattern)),
          coll  = stri_endswith_coll(string,  pattern, negate = negate, opts_collator = opts(pattern)),
          regex = {
-           pattern2 <- paste0(pattern, "$")
+           pattern2 <- paste0("(", pattern, ")$")
            attributes(pattern2) <- attributes(pattern)
            str_detect(string, pattern2, negate)
          }

tests/testthat/test-detect.r

@@ -36,6 +36,10 @@ test_that("str_starts works", {
   # Special typing of patterns.
   expect_true(str_starts("ab", fixed("A", ignore_case = TRUE)))
   expect_true(str_starts("ab", regex("A", ignore_case = TRUE)))
+
+  # Or operators are respected
+  expect_true(str_starts("ab", "b|a"))
+  expect_false(str_starts("ab", "c|b"))
 })
 
 test_that("str_ends works", {
@@ -48,6 +52,10 @@ test_that("str_ends works", {
 
   # Special typing of patterns.
   expect_true(str_ends("ab", fixed("B", ignore_case = TRUE)))
+
+  # Or operators are respected
+  expect_true(str_ends("ab", "b|a"))
+  expect_false(str_ends("ab", "c|a"))
 })