Validate user-provided pit at the entry point

NEWS.md

@@ -1,5 +1,6 @@
 # bayesplot (development version)
 
+* Validate user-provided `pit` values in `ppc_loo_pit_data()` using `validate_pit()` to reject invalid inputs (non-numeric, out of range, NAs) at the entry point instead of in internal helpers.
 * Added unit tests for `ppc_error_data()` and `ppc_loo_pit_data()` covering output structure, argument handling, and edge cases.
 * Added vignette sections demonstrating `*_data()` companion functions for building custom ggplot2 visualizations (#435)
 * Extract `drop_singleton_values()` helper in `mcmc_nuts_treedepth()` to remove duplicated filtering logic.

R/ppc-loo.R

@@ -302,7 +302,7 @@ ppc_loo_pit_data <-
            boundary_correction = TRUE,
            grid_len = 512) {
     if (!is.null(pit)) {
-      stopifnot(is.numeric(pit), is_vector_or_1Darray(pit))
+      pit <- validate_pit(pit)
       inform("'pit' specified so ignoring 'y','yrep','lw' if specified.")
     } else {
       suggested_package("rstantools")
@@ -795,14 +795,6 @@ ppc_loo_ribbon <-
   # Generate boundary corrected values via a linear convolution using a
   # 1-D Gaussian window filter. This method uses the "reflection method"
   # to estimate these pvalues and helps speed up the code
-  if (any(is.infinite(x))) {
-    warn(paste(
-      "Ignored", sum(is.infinite(x)),
-      "Non-finite PIT values are invalid for KDE boundary correction method"
-    ))
-    x <- x[is.finite(x)]
-  }
-
   if (grid_len < 100) {
     grid_len <- 100
   }
@@ -824,6 +816,10 @@ ppc_loo_ribbon <-
 
   xs <- (grid_breaks[2:n_breaks] + grid_breaks[1:(n_breaks - 1)]) / 2
 
+  if (all(is.na(bc_pvals))) {
+    abort("KDE boundary correction produced all NA values.")
+  }
+
   first_nonNA <- utils::head(which(!is.na(bc_pvals)), 1)
   last_nonNA <- utils::tail(which(!is.na(bc_pvals)), 1)
   bc_pvals[1:first_nonNA] <- bc_pvals[first_nonNA]

tests/testthat/test-ppc-loo.R

@@ -59,17 +59,23 @@ test_that("ppc_loo_pit_overlay works with boundary_correction=FALSE", {
   expect_gg(p1)
 })
 
-test_that(".kde_correction warns when PIT values are non-finite", {
-  set.seed(123)
-  pit_vals <- c(stats::runif(500), Inf)
-  expect_warning(
-    out <- .kde_correction(pit_vals, bw = "nrd0", grid_len = 128),
-    "Non-finite PIT values are invalid"
+test_that("ppc_loo_pit_data validates user-provided pit values", {
+  expect_error(
+    ppc_loo_pit_data(pit = c(0.5, Inf)),
+    "between 0 and 1"
+  )
+  expect_error(
+    ppc_loo_pit_data(pit = c(-1, 0.5)),
+    "between 0 and 1"
+  )
+  expect_error(
+    ppc_loo_pit_data(pit = c(0.5, NA)),
+    "NAs not allowed"
+  )
+  expect_error(
+    ppc_loo_pit_data(pit = "not numeric"),
+    "is.numeric"
   )
-  expect_type(out, "list")
-  expect_true(all(c("xs", "bc_pvals") %in% names(out)))
-  expect_equal(length(out$xs), 128)
-  expect_equal(length(out$bc_pvals), 128)
 })
 
 test_that("ppc_loo_pit_qq returns ggplot object", {