add test

Author: jgabry

R/model.R

@@ -686,8 +686,12 @@ compile <- function(quiet = TRUE,
       )
     )
     if (is.na(run_log$status) || run_log$status != 0) {
-      stop("An error occured during compilation! See the message above for more information.",
-           call. = FALSE)
+      err_msg <- "An error occured during compilation! See the message above for more information."
+      if (grepl("auto-format flag to stanc", run_log$stderr)) {
+        format_msg <- "\nTo fix deprecated or removed syntax please see ?cmdstanr::format for an example."
+        err_msg <- paste(err_msg, format_msg)
+      }
+      stop(err_msg, call. = FALSE)
     }
     if (file.exists(exe)) {
       file.remove(exe)

tests/testthat/resources/stan/old_array_syntax.stan

@@ -0,0 +1,6 @@
+parameters {
+  real x[3];
+}
+model {
+  x ~ normal(0, 1);
+}

tests/testthat/test-model-compile.R

@@ -174,6 +174,15 @@ test_that("compile errors are shown", {
   )
 })
 
+test_that("compile suggests using format to fix old syntax", {
+  stan_file <- testing_stan_file("old_array_syntax")
+  expect_error(
+    cmdstan_model(stan_file),
+    "To fix deprecated or removed syntax please see ?cmdstanr::format for an example.",
+    fixed = TRUE
+  )
+})
+
 test_that("dir arg works for cmdstan_model and $compile()", {
   tmp_dir <- tempdir()
   tmp_dir_2 <- tempdir()