Fix validate_chain_list() colnames check to compare all chains

NEWS.md

@@ -1,6 +1,6 @@
 # bayesplot (development version)
 
-
+* Fixed `validate_chain_list()` colnames check to compare all chains, not just the first two.
 * 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.
 * Fixed missing `drop = FALSE` in `nuts_params.CmdStanMCMC()`.

R/helpers-mcmc.R

@@ -277,12 +277,8 @@ validate_chain_list <- function(x) {
       abort("Each chain should have the same number of iterations.")
     }
 
-    cnames <- sapply(x, colnames)
-    if (is.array(cnames)) {
-      same_params <- identical(cnames[, 1], cnames[, 2])
-    } else {
-      same_params <- length(unique(cnames)) == 1
-    }
+    cnames <- lapply(x, colnames)
+    same_params <- all(vapply(cnames[-1], identical, logical(1), cnames[[1]]))
     if (!same_params) {
       abort(paste(
         "The parameters for each chain should be in the same order",

tests/testthat/test-helpers-mcmc.R

@@ -178,6 +178,18 @@ test_that("validate_chain_list works", {
                "Each chain should have the same number of iterations")
 })
 
+test_that("validate_chain_list detects colnames mismatch in chain 3+", {
+  ch <- matrix(rnorm(20), nrow = 2, dimnames = list(NULL, c("a", "b", "c", "d", "e",
+                                                             "f", "g", "h", "i", "j")))
+  chain3_bad <- ch
+  colnames(chain3_bad)[1] <- "z"
+  chains_ok <- list(ch, ch, ch)
+  chains_bad <- list(ch, ch, chain3_bad)
+
+  expect_identical(validate_chain_list(chains_ok), chains_ok)
+  expect_error(validate_chain_list(chains_bad), "parameters for each chain")
+})
+
 test_that("chain_list2array works", {
   expect_mcmc_array(chain_list2array(chainlist))
   expect_mcmc_array(chain_list2array(chainlist1))