From 2418f24b609029c3f3415b5954005d5aa4851f0b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Markb=C3=A5ge?= <sema@fb.com>
Date: Thu, 3 Jun 2021 09:13:00 -0400
Subject: [PATCH] Fix <select> check of defaultValue/value type (#21611)

---
 .../src/server/ReactDOMServerFormatConfig.js  | 29 ++++++++++---------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/packages/react-dom/src/server/ReactDOMServerFormatConfig.js b/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
index 09ac84a673..7d705a6abe 100644
--- a/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
+++ b/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
@@ -568,19 +568,22 @@ let didWarnSelectedSetOnOption = false;
 
 function checkSelectProp(props, propName) {
   if (__DEV__) {
-    const array = isArray(props[propName]);
-    if (props.multiple && !array) {
-      console.error(
-        'The `%s` prop supplied to <select> must be an array if ' +
-          '`multiple` is true.',
-        propName,
-      );
-    } else if (!props.multiple && array) {
-      console.error(
-        'The `%s` prop supplied to <select> must be a scalar ' +
-          'value if `multiple` is false.',
-        propName,
-      );
+    const value = props[propName];
+    if (value != null) {
+      const array = isArray(value);
+      if (props.multiple && !array) {
+        console.error(
+          'The `%s` prop supplied to <select> must be an array if ' +
+            '`multiple` is true.',
+          propName,
+        );
+      } else if (!props.multiple && array) {
+        console.error(
+          'The `%s` prop supplied to <select> must be a scalar ' +
+            'value if `multiple` is false.',
+          propName,
+        );
+      }
     }
   }
 }