Fix edge-case validation in nuts_params.list()

NEWS.md

@@ -1,5 +1,6 @@
 # bayesplot (development version)
 
+* Validate empty list and zero-row matrix inputs in `nuts_params.list()`.
 * Validate user-provided `pit` values in `ppc_loo_pit_data()` and `ppc_loo_pit_qq()`, rejecting non-numeric inputs, missing values, and values outside `[0, 1]`.
 * New `show_marginal` argument to `ppd_*()` functions to show the PPD - the marginal predictive distribution by @mattansb (#425)
 * `ppc_ecdf_overlay()`, `ppc_ecdf_overlay_grouped()`, and `ppd_ecdf_overlay()` now always use `geom_step()`. The `discrete` argument is deprecated.

R/bayesplot-extractors.R

@@ -145,10 +145,18 @@ nuts_params.stanreg <-
 #' @export
 #' @method nuts_params list
 nuts_params.list <- function(object, pars = NULL, ...) {
+  if (length(object) == 0) {
+    abort("'object' must be a non-empty list.")
+  }
+
   if (!all(sapply(object, is.matrix))) {
     abort("All list elements should be matrices.")
   }
 
+  if (any(vapply(object, nrow, integer(1)) == 0)) {
+    abort("All matrices in the list must have at least one row.")
+  }
+
   dd <- lapply(object, dim)
   if (length(unique(dd)) != 1) {
     abort("All matrices in the list must have the same dimensions.")

tests/testthat/test-extractors.R

@@ -9,6 +9,8 @@ x <- list(cbind(a = 1:3, b = rnorm(3)), cbind(a = 1:3, b = rnorm(3)))
 
 # nuts_params and log_posterior methods -----------------------------------
 test_that("nuts_params.list throws errors", {
+  expect_error(nuts_params.list(list()), "non-empty list")
+
   x[[3]] <- c(a = 1:3, b = rnorm(3))
   expect_error(nuts_params.list(x), "list elements should be matrices")
 
@@ -17,6 +19,20 @@ test_that("nuts_params.list throws errors", {
 
   x[[3]] <- cbind(a = 1:4, b = rnorm(4))
   expect_error(nuts_params.list(x), "same dimensions")
+
+  zero_row <- list(cbind(a = numeric(0), b = numeric(0)))
+  expect_error(nuts_params.list(zero_row), "at least one row")
+
+  zero_row_nonfirst <- list(cbind(a = 1:3, b = rnorm(3)), cbind(a = numeric(0), b = numeric(0)))
+  expect_error(nuts_params.list(zero_row_nonfirst), "at least one row")
+})
+
+test_that("nuts_params.list works with single-chain list", {
+  single <- list(cbind(a = 1:3, b = rnorm(3)))
+  np <- nuts_params.list(single)
+  expect_identical(colnames(np), c("Chain", "Iteration", "Parameter", "Value"))
+  expect_true(all(np$Chain == 1L))
+  expect_equal(nrow(np), 6L)
 })
 
 test_that("nuts_params.list parameter selection ok", {