From ff8e36d42ac02282d750abaf684885e265343a3a Mon Sep 17 00:00:00 2001
From: Felipe Mesquita <femesq@gmail.com>
Date: Tue, 27 Oct 2020 09:48:10 -0300
Subject: [PATCH] Fix #9880

Fix formatting error on webpack v5 (https://github.com/facebook/create-react-app/issues/9880).
---
 packages/react-dev-utils/formatWebpackMessages.js | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/packages/react-dev-utils/formatWebpackMessages.js b/packages/react-dev-utils/formatWebpackMessages.js
index 68afa222817..9a33d510c68 100644
--- a/packages/react-dev-utils/formatWebpackMessages.js
+++ b/packages/react-dev-utils/formatWebpackMessages.js
@@ -16,7 +16,13 @@ function isLikelyASyntaxError(message) {
 
 // Cleans up webpack error messages.
 function formatMessage(message) {
-  let lines = message.split('\n');
+  let lines = [];
+
+  if (typeof lines === 'string' || lines instanceof String) {
+    lines = message.split('\n');
+  } else if ('message' in Object.keys(lines)) {
+    lines = message['message'].split('\n');
+  }
 
   // Strip webpack-added headers off errors/warnings
   // https://github.com/webpack/webpack/blob/master/lib/ModuleError.js