Merge pull request #1046 from stan-dev/no-fixed-param-error

Don't require `fixed_param` for models with zero parameters (only GQs) for CmdStan >= 2.36

Author: jgabry

R/csv.R

@@ -719,7 +719,7 @@ read_csv_metadata <- function(csv_file) {
         dense_inv_metric <- TRUE
       } else if (inv_metric_next) {
         inv_metric_split <- strsplit(gsub("# ", "", line), ",")
-        numeric_inv_metric_split <- rapply(inv_metric_split, as.numeric)
+        numeric_inv_metric_split <- suppressWarnings(rapply(inv_metric_split, as.numeric))
         if (inv_metric_rows == -1 && dense_inv_metric) {
           inv_metric_rows <- length(inv_metric_split[[1]])
           inv_metric_rows_to_read <- inv_metric_rows
@@ -786,6 +786,7 @@ read_csv_metadata <- function(csv_file) {
     }
   }
   if (csv_file_info$method != "diagnose" &&
+      !isTRUE(csv_file_info$algorithm == "fixed_param") &&
       length(csv_file_info$sampler_diagnostics) == 0 &&
       length(csv_file_info$variables) == 0) {
     stop("Supplied CSV file does not contain any variable names or data!", call. = FALSE)

R/model.R

@@ -1208,7 +1208,7 @@ sample <- function(data = NULL,
     }
   }
 
-  if (cmdstan_version() >= "2.27.0" && !fixed_param) {
+  if (cmdstan_version() >= "2.27.0" && cmdstan_version() < "2.36.0" && !fixed_param) {
     if (self$has_stan_file() && file.exists(self$stan_file())) {
       if (!is.null(self$variables()) && length(self$variables()$parameters) == 0) {
         stop("Model contains no parameters. Please use 'fixed_param = TRUE'.", call. = FALSE)

tests/testthat/test-model-sample.R

@@ -307,7 +307,7 @@ test_that("seed works for multi chain sampling", {
   expect_false(all(chain_tdata_1 == chain_tdata_2))
 })
 
-test_that("fixed_param is set when the model has no parameters", {
+test_that("Correct behavior if fixed_param not set when the model has no parameters", {
   code <- "
   model {}
   generated quantities  {
@@ -316,10 +316,21 @@ test_that("fixed_param is set when the model has no parameters", {
   "
   stan_file <- write_stan_file(code)
   m <- cmdstan_model(stan_file)
+  fake_cmdstan_version("2.35.0")
   expect_error(
     m$sample(),
     "Model contains no parameters. Please use 'fixed_param = TRUE'."
   )
+
+  reset_cmdstan_version()
+  if (cmdstan_version() >= "2.36.0") {
+    # as of 2.36.0 we don't need fixed_param if no parameters
+    expect_no_error(
+      utils::capture.output(
+        fit <- m$sample(iter_warmup = 10, iter_sampling = 10, diagnostics = NULL)
+      )
+    )
+  }
 })
 
 test_that("sig_figs warning if version less than 2.25", {