Make macOS platform detection more robust

If we don't know the platform, then take the last row.

R/platform.R

@@ -321,7 +321,11 @@ macos_cran_platforms$rversion <- get_minor_r_version(
 macos_cran_platforms <- unique(macos_cran_platforms)
 
 get_cran_macos_platform <- function(v) {
-  macos_cran_platforms[macos_cran_platforms$rversion %in% v,,drop = FALSE]
+  if (v %in% macos_cran_platforms$rversion) {
+    macos_cran_platforms[macos_cran_platforms$rversion %in% v,,drop = FALSE]
+  } else {
+    utils::tail(macos_cran_platforms, 2)
+  }
 }
 
 #' Query the default CRAN repository for this session

tests/testthat/_snaps/macos-platforms.md

@@ -0,0 +1,45 @@
+# macos platforms
+
+    Code
+      get_cran_macos_platform("4.2")
+    Output
+         rversion                platform        subdir
+      35      4.2 x86_64-apple-darwin17.0              
+      36      4.2  aarch64-apple-darwin20 big-sur-arm64
+    Code
+      get_cran_macos_platform("4.3")
+    Output
+         rversion               platform         subdir
+      37      4.3  x86_64-apple-darwin20 big-sur-x86_64
+      38      4.3 aarch64-apple-darwin20  big-sur-arm64
+    Code
+      get_cran_macos_platform("4.4")
+    Output
+         rversion               platform         subdir
+      39      4.4  x86_64-apple-darwin20 big-sur-x86_64
+      40      4.4 aarch64-apple-darwin20  big-sur-arm64
+    Code
+      get_cran_macos_platform("4.5")
+    Output
+         rversion               platform         subdir
+      41      4.5  x86_64-apple-darwin20 big-sur-x86_64
+      42      4.5 aarch64-apple-darwin20  big-sur-arm64
+    Code
+      get_cran_macos_platform("4.6")
+    Output
+         rversion               platform         subdir
+      43      4.6  x86_64-apple-darwin20 big-sur-x86_64
+      44      4.6 aarch64-apple-darwin20  big-sur-arm64
+    Code
+      get_cran_macos_platform("5.0")
+    Output
+         rversion               platform         subdir
+      45      5.0  x86_64-apple-darwin20 big-sur-x86_64
+      46      5.0 aarch64-apple-darwin20  big-sur-arm64
+    Code
+      get_cran_macos_platform("10.0")
+    Output
+         rversion               platform         subdir
+      45      5.0  x86_64-apple-darwin20 big-sur-x86_64
+      46      5.0 aarch64-apple-darwin20  big-sur-arm64
+

tests/testthat/test-macos-platforms.R

@@ -0,0 +1,25 @@
+test_that("macos platforms", {
+  skip_on_cran()
+  expect_snapshot({
+    get_cran_macos_platform("4.2")
+    get_cran_macos_platform("4.3")
+    get_cran_macos_platform("4.4")
+    get_cran_macos_platform("4.5")
+    get_cran_macos_platform("4.6")
+    get_cran_macos_platform("5.0")
+    get_cran_macos_platform("10.0")
+  })
+
+  # error if we don't know the platform
+  # we do this so we can detect the failure on the CI and update
+  # the platform
+  v <- paste0(getRversion()[,1:2])
+  expect_true(v %in% macos_cran_platforms$rversion)
+
+  # In case CRAN changes the platform for R-devel
+  if (Sys.info()[["sysname"]] == "Darwin" && .Platform$pkgType != "source") {
+    plt <- get_cran_macos_platform(v)
+    expect_true(R.Version()$platform %in% plt$platform)
+    expect_true(.Platform$pkgType %in% paste0("mac.binary.", plt$subdir))
+  }
+})