From 48e2c19de0423dbd10b9e1791854d6214f0023fd Mon Sep 17 00:00:00 2001
From: Joe Haddad <joe.haddad@zeit.co>
Date: Fri, 17 Apr 2020 13:38:09 -0400
Subject: [PATCH] Serialize JSON Warnings Before Event (#11976)

---
 packages/next/build/output/index.ts | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/packages/next/build/output/index.ts b/packages/next/build/output/index.ts
index c01bc2ac236ea..591f32bf96a2e 100644
--- a/packages/next/build/output/index.ts
+++ b/packages/next/build/output/index.ts
@@ -336,13 +336,15 @@ export function watchCompilers(
 
             stats.compilation.errors.push(...(filteredErrors || []))
             stats.compilation.warnings.push(...(filteredWarnings || []))
+            const {
+              errors: newErrors,
+              warnings: newWarnings,
+            } = formatWebpackMessages(
+              stats.toJson({ all: false, warnings: true, errors: true })
+            )
             onTypeChecked({
-              errors: stats.compilation.errors.length
-                ? stats.compilation.errors
-                : null,
-              warnings: stats.compilation.warnings.length
-                ? stats.compilation.warnings
-                : null,
+              errors: newErrors?.length ? newErrors : null,
+              warnings: newWarnings?.length ? newWarnings : null,
             })
 
             onEvent({