From 897f6fe591350135243f7c26819109e424d573dd Mon Sep 17 00:00:00 2001
From: jgabry <jgabry@gmail.com>
Date: Fri, 8 May 2026 12:24:54 +0200
Subject: [PATCH] `$lp_approx()`, `$mle()` return numeric vectors even if
 default draws format is not a matrix

---
 R/fit.R                           |  7 ++++---
 tests/testthat/test-fit-laplace.R | 13 +++++++++++++
 tests/testthat/test-fit-mle.R     | 11 +++++++++++
 tests/testthat/test-fit-vb.R      | 13 +++++++++++++
 4 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/R/fit.R b/R/fit.R
index ead1f0a1..73df4476 100644
--- a/R/fit.R
+++ b/R/fit.R
@@ -768,7 +768,8 @@ CmdStanFit$set("public", name = "lp", value = lp)
 # will be used by a subset of fit objects below
 #' @rdname fit-method-lp
 lp_approx <- function() {
-  as.numeric(self$draws()[, "lp_approx__"])
+  x <- self$draws(variables = "lp_approx__", format = "draws_matrix")
+  as.numeric(x[, "lp_approx__"])
 }
 
 
@@ -1973,8 +1974,8 @@ CmdStanMLE <- R6::R6Class(
 #' }
 #'
 mle <- function(variables = NULL) {
-  x <- self$draws(variables)
-  x <- x[, colnames(x) != "lp__"]
+  x <- self$draws(variables = variables, format = "draws_matrix")
+  x <- x[, colnames(x) != "lp__", drop = FALSE]
   stats::setNames(as.numeric(x), posterior::variables(x))
 }
 CmdStanMLE$set("public", name = "mle", value = mle)
diff --git a/tests/testthat/test-fit-laplace.R b/tests/testthat/test-fit-laplace.R
index 54933eef..b2258a58 100644
--- a/tests/testthat/test-fit-laplace.R
+++ b/tests/testthat/test-fit-laplace.R
@@ -41,6 +41,19 @@ test_that("lp(), lp_approx() methods return vectors (reading csv works)", {
   expect_equal(length(lg), length(lp))
 })
 
+test_that("lp_approx() ignores non-matrix default draws formats", {
+  expected <- fit_laplace$draws(
+    variables = "lp_approx__",
+    format = "draws_matrix"
+  )
+  expected <- as.numeric(expected[, "lp_approx__"])
+
+  for (format in c("draws_array", "draws_df")) {
+    withr::local_options(list(cmdstanr_draws_format = format))
+    expect_equal(fit_laplace$lp_approx(), expected)
+  }
+})
+
 test_that("time() method works after laplace", {
   run_times <- fit_laplace$time()
   checkmate::expect_list(run_times, names = "strict", any.missing = FALSE)
diff --git a/tests/testthat/test-fit-mle.R b/tests/testthat/test-fit-mle.R
index e65b9205..db970a1c 100644
--- a/tests/testthat/test-fit-mle.R
+++ b/tests/testthat/test-fit-mle.R
@@ -10,6 +10,17 @@ test_that("mle and lp methods work after optimization", {
   checkmate::expect_numeric(fit_mle$lp(), len = 1)
 })
 
+test_that("mle() ignores non-matrix default draws formats", {
+  expected <- fit_mle$draws(format = "draws_matrix")
+  expected <- expected[, colnames(expected) != "lp__", drop = FALSE]
+  expected <- stats::setNames(as.numeric(expected), posterior::variables(expected))
+
+  for (format in c("draws_array", "draws_df")) {
+    withr::local_options(list(cmdstanr_draws_format = format))
+    expect_equal(fit_mle$mle(), expected)
+  }
+})
+
 test_that("summary method works after optimization", {
   x <- fit_mle$summary()
   expect_s3_class(x, "draws_summary")
diff --git a/tests/testthat/test-fit-vb.R b/tests/testthat/test-fit-vb.R
index bac2d079..986f38eb 100644
--- a/tests/testthat/test-fit-vb.R
+++ b/tests/testthat/test-fit-vb.R
@@ -71,6 +71,19 @@ test_that("lp(), lp_approx() methods return vectors (reading csv works)", {
   expect_equal(length(lg), length(lp))
 })
 
+test_that("lp_approx() ignores non-matrix default draws formats", {
+  expected <- fit_vb$draws(
+    variables = "lp_approx__",
+    format = "draws_matrix"
+  )
+  expected <- as.numeric(expected[, "lp_approx__"])
+
+  for (format in c("draws_array", "draws_df")) {
+    withr::local_options(list(cmdstanr_draws_format = format))
+    expect_equal(fit_vb$lp_approx(), expected)
+  }
+})
+
 test_that("vb works with scientific notation args", {
   x <- fit_vb_sci_not$summary()
   expect_s3_class(x, "draws_summary")