From 7ff6d44efaf5dfe09320f2a67a1c8ae99370c62b Mon Sep 17 00:00:00 2001
From: david-cortes <david.cortes.rivera@gmail.com>
Date: Mon, 8 Jan 2024 20:43:21 +0100
Subject: [PATCH] [R] Use R's error stream for printing warnings (#9965)

---
 R-package/src/xgboost_custom.cc       | 6 +++++-
 R-package/tests/testthat/test_basic.R | 3 ++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/R-package/src/xgboost_custom.cc b/R-package/src/xgboost_custom.cc
index f196297ec..6aaa3696a 100644
--- a/R-package/src/xgboost_custom.cc
+++ b/R-package/src/xgboost_custom.cc
@@ -17,7 +17,11 @@ namespace xgboost {
 ConsoleLogger::~ConsoleLogger() {
   if (cur_verbosity_ == LogVerbosity::kIgnore ||
       cur_verbosity_ <= GlobalVerbosity()) {
-    dmlc::CustomLogMessage::Log(log_stream_.str());
+    if (cur_verbosity_ == LogVerbosity::kWarning) {
+      REprintf("%s\n", log_stream_.str().c_str());
+    } else {
+      dmlc::CustomLogMessage::Log(log_stream_.str());
+    }
   }
 }
 TrackerLogger::~TrackerLogger() {
diff --git a/R-package/tests/testthat/test_basic.R b/R-package/tests/testthat/test_basic.R
index d4b3a6be3..1f6cebbca 100644
--- a/R-package/tests/testthat/test_basic.R
+++ b/R-package/tests/testthat/test_basic.R
@@ -83,7 +83,8 @@ test_that("parameter validation works", {
       bar = "foo"
     )
     output <- capture.output(
-      xgb.train(params = params, data = dtrain, nrounds = nrounds)
+      xgb.train(params = params, data = dtrain, nrounds = nrounds),
+      type = "message"
     )
     print(output)
   }