Add handling and tests for floating-pointness

R/data.R

@@ -189,8 +189,12 @@ process_data <- function(data, model_variables = NULL) {
           if (!all(is_wholenumber(data[[var_name]]))) {
             warning("A non-integer value was supplied for '", var_name, "'!",
                     " It will be truncated to an integer.", call. = FALSE)
+            mode(data[[var_name]]) <- "integer"
+          } else {
+            # Round before setting mode to integer to avoid floating point errors
+            data[[var_name]] <- round(data[[var_name]])
+            mode(data[[var_name]]) <- "integer"
           }
-          mode(data[[var_name]]) <- "integer"
         }
       }
     }

tests/testthat/test-data.R

@@ -384,3 +384,21 @@ test_that("process_data warns on int coercion", {
     process_data(list(a = c(1, 2, 3)), model_variables = mod$variables())
   )
 })
+
+test_that("Floating-point differences do not cause truncation towards 0", {
+  stan_file <- write_stan_file("
+  data {
+    int a;
+    real b;
+  }
+  ")
+  mod <- cmdstan_model(stan_file, compile = FALSE)
+  a <- 10*(3-2.7)
+  expect_false(is.integer(a))
+  test_file <- process_data(list(a = a, b = 2.0), model_variables = mod$variables())
+  expect_match(
+    "  \"a\": 3,",
+    readLines(test_file)[2],
+    fixed = TRUE
+  )
+})