Fix split of os and os-release in system_requirements, and add unit test

NEWS.md

@@ -1,5 +1,7 @@
 # remotes (development version)
 
+* `system_requirements()` now works as intended if only the `os` argument is used (@mdneuzerling, #609)
+
 * skip tests for `download.file(method = "internal")`, on R > 4.1, since that method is now defunct on those versions.
 
 * Re-license as MIT. (#551)

R/system_requirements.R

@@ -19,7 +19,7 @@ DEFAULT_RSPM <-  "https://packagemanager.rstudio.com"
 #' @export
 system_requirements <- function(os, os_release = NULL, path = ".", package = NULL, curl = Sys.which("curl")) {
   if (is.null(os_release)) {
-    os_release <- strsplit(os_release, "-", fixed = TRUE)[[1]]
+    os_release <- strsplit(os, "-", fixed = TRUE)[[1]]
     if (length(os_release) != 2) {
       stop("If os_release is missing, os must consist of name and release.", call. = FALSE)
     }

tests/testthat/test-system_requirements.R

@@ -160,3 +160,16 @@ test_that("system_requirements work with package arguments", {
     )
   )
 })
+
+test_that("system_requirements allow specifying os_release within os", {
+  skip_on_cran()
+  skip_if_offline()
+
+  expect_equal(
+    system_requirements("ubuntu-16.04", package = "curl"),
+    c("apt-get install -y libcurl4-openssl-dev",
+      "apt-get install -y libssl-dev"
+    )
+  )
+})
+