From 77a476de8a8016e55a65d3de8438dca013fb5079 Mon Sep 17 00:00:00 2001
From: Andrew Johnson <andrew.johnson@arjohnsonau.com>
Date: Thu, 23 Mar 2023 18:41:56 +0200
Subject: [PATCH 1/4] Add version check when exposing external functions

---
 R/model.R                                    |  1 +
 R/utils.R                                    |  4 ++++
 tests/testthat/test-model-expose-functions.R | 22 ++++++++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/R/model.R b/R/model.R
index 1de220b69..ff5b637e4 100644
--- a/R/model.R
+++ b/R/model.R
@@ -582,6 +582,7 @@ compile <- function(quiet = TRUE,
   }
   stancflags_standalone <- c("--standalone-functions", stancflags_val, stancflags_combined)
   self$functions$hpp_code <- get_standalone_hpp(temp_stan_file, stancflags_standalone)
+  self$functions$external <- !is.null(user_header)
   if (compile_standalone) {
     expose_functions(self$functions, !quiet)
   }
diff --git a/R/utils.R b/R/utils.R
index c32f50ea7..8317e293f 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -878,6 +878,10 @@ expose_functions <- function(function_env, global = FALSE, verbose = FALSE) {
           "WSL CmdStan and will not be compiled",
           call. = FALSE)
   }
+  if (function_env$external && cmdstan_version() < "2.32") {
+    stop("Exporting standalone functions with external C++ is not available before CmdStan 2.32",
+         call. = FALSE)
+  }
   require_suggested_package("Rcpp")
   require_suggested_package("RcppEigen")
   require_suggested_package("decor")
diff --git a/tests/testthat/test-model-expose-functions.R b/tests/testthat/test-model-expose-functions.R
index dfc2f74c4..c5808aad0 100644
--- a/tests/testthat/test-model-expose-functions.R
+++ b/tests/testthat/test-model-expose-functions.R
@@ -147,3 +147,25 @@ test_that("Overloaded functions give meaningful errors", {
   expect_error(funmod$expose_functions(),
                "Overloaded functions are currently not able to be exposed to R! The following overloaded functions were found: fun1, fun3")
 })
+
+test_that("Exposing external functions errors before v2.32", {
+  tmpfile <- tempfile(fileext = ".hpp")
+  hpp <-
+  "
+  #include <ostream>
+  namespace standalone_external_model_namespace {
+    int rtn_int(int x, std::ostream *pstream__) { return x; }
+  }"
+  cat(hpp, file = tmpfile, sep = "\n")
+  stanfile <- file.path(tempdir(), "standalone_external.stan")
+  cat("functions { int rtn_int(int x); }\n", file = stanfile)
+  expect_error({
+    cmdstan_model(
+      stan_file = stanfile,
+      user_header = tmpfile,
+      compile_standalone = TRUE
+    )
+  },
+  "Exporting standalone functions with external C++ is not available before CmdStan 2.32",
+  fixed = TRUE)
+})

From c112f37f0dbc4c1c2f56e9701fb1c6b297ba6f57 Mon Sep 17 00:00:00 2001
From: Andrew Johnson <andrew.johnson@arjohnsonau.com>
Date: Thu, 23 Mar 2023 18:55:05 +0200
Subject: [PATCH 2/4] Use fixed version in test

---
 tests/testthat/test-model-expose-functions.R | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tests/testthat/test-model-expose-functions.R b/tests/testthat/test-model-expose-functions.R
index c5808aad0..27ebd05d3 100644
--- a/tests/testthat/test-model-expose-functions.R
+++ b/tests/testthat/test-model-expose-functions.R
@@ -149,6 +149,16 @@ test_that("Overloaded functions give meaningful errors", {
 })
 
 test_that("Exposing external functions errors before v2.32", {
+  if (getRversion() < '3.5.0') {
+    dir <- tempdir()
+  } else {
+    dir <- tempdir(check = TRUE)
+  }
+  install_cmdstan(dir = dir, cores = 2, quiet = FALSE,
+                  overwrite = TRUE, version = "2.31.0",
+                  wsl = os_is_wsl())
+  set_cmdstan_path(dir)
+
   tmpfile <- tempfile(fileext = ".hpp")
   hpp <-
   "

From 552901464700f03fe9817ec6b07861888f2b96f1 Mon Sep 17 00:00:00 2001
From: Andrew Johnson <andrew.johnson@arjohnsonau.com>
Date: Thu, 23 Mar 2023 20:29:05 +0200
Subject: [PATCH 3/4] Fix test failure

---
 tests/testthat/test-model-expose-functions.R | 1 -
 1 file changed, 1 deletion(-)

diff --git a/tests/testthat/test-model-expose-functions.R b/tests/testthat/test-model-expose-functions.R
index 27ebd05d3..a88ea320b 100644
--- a/tests/testthat/test-model-expose-functions.R
+++ b/tests/testthat/test-model-expose-functions.R
@@ -157,7 +157,6 @@ test_that("Exposing external functions errors before v2.32", {
   install_cmdstan(dir = dir, cores = 2, quiet = FALSE,
                   overwrite = TRUE, version = "2.31.0",
                   wsl = os_is_wsl())
-  set_cmdstan_path(dir)
 
   tmpfile <- tempfile(fileext = ".hpp")
   hpp <-

From 36427554c2f09eeedc8df4b9b4668bd251937dd5 Mon Sep 17 00:00:00 2001
From: Andrew Johnson <andrew.johnson@arjohnsonau.com>
Date: Thu, 23 Mar 2023 22:12:42 +0200
Subject: [PATCH 4/4] Missed wsl skip

---
 tests/testthat/test-model-expose-functions.R | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tests/testthat/test-model-expose-functions.R b/tests/testthat/test-model-expose-functions.R
index a88ea320b..3be219e0f 100644
--- a/tests/testthat/test-model-expose-functions.R
+++ b/tests/testthat/test-model-expose-functions.R
@@ -149,6 +149,8 @@ test_that("Overloaded functions give meaningful errors", {
 })
 
 test_that("Exposing external functions errors before v2.32", {
+  skip_if(os_is_wsl())
+
   if (getRversion() < '3.5.0') {
     dir <- tempdir()
   } else {