str_interp() formatting of interpolated list depends on presence other interpolated expressions

NEWS.md

@@ -1,5 +1,8 @@
 # stringr 1.3.1.9000
 
+* `str_interp()` now renders lists consistently independent on the presence of
+  additional placeholders (@amhrasmussen)
+
 # stringr 1.3.1
 
 * `str_replace_all()` with a named vector now respects modifier functions (#207)

R/interp.R

@@ -143,7 +143,7 @@ eval_interp_matches <- function(matches, env) {
   formats <- extract_formats(matches)
 
   # Format the values and return.
-  mapply(sprintf, formats, values)
+  mapply(sprintf, formats, values, SIMPLIFY = FALSE)
 }
 
 #' Extract Expression Objects from String Interpolation Matches

tests/testthat/test-interp.r

@@ -68,3 +68,12 @@ test_that("str_interp fails when encountering nested placeholders", {
 test_that("str_interp fails when input is not a character string", {
   expect_error(str_interp(3L))
 })
+
+test_that("str_interp formats list independetly of other placeholders", {
+  a_list <- c("item1", "item2", "item3")
+  other <- "1"
+  extract <- function(text) regmatches(text, regexpr("xx[^x]+xx", text))
+  from_list <- extract(str_interp("list: xx${a_list}xx"))
+  from_both <- extract(str_interp("list: xx${a_list}xx, and another ${other}"))
+  expect_equal(from_list, from_both)
+})