From 7ee7ddc38afc5131985dea6010267ada77f4a37e Mon Sep 17 00:00:00 2001
From: Will Binns-Smith <wbinnssmith@gmail.com>
Date: Wed, 30 Aug 2023 20:25:26 -0700
Subject: [PATCH] Don't send tracing spans if performance.measure doesn't
 return measurements

Fixes #54389.

Old versions of Safari appear to return `undefined` from `performance.measure()` instead of `PerformanceMeasure` values.
---
 packages/next/src/client/index.tsx | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/packages/next/src/client/index.tsx b/packages/next/src/client/index.tsx
index cd0a8d601bfb2..3432464e29093 100644
--- a/packages/next/src/client/index.tsx
+++ b/packages/next/src/client/index.tsx
@@ -466,19 +466,22 @@ function markHydrateComplete(): void {
     'afterHydrate'
   )
 
-  tracer
-    .startSpan('navigation-to-hydration', {
-      startTime: performance.timeOrigin + beforeHydrationMeasure.startTime,
-      attributes: {
-        pathname: location.pathname,
-        query: location.search,
-      },
-    })
-    .end(
-      performance.timeOrigin +
-        hydrationMeasure.startTime +
-        hydrationMeasure.duration
-    )
+  if (beforeHydrationMeasure !== undefined && hydrationMeasure !== undefined) {
+    // Old versions of Safari don't return `PerformanceMeasure`s from `performance.measure()`
+    tracer
+      .startSpan('navigation-to-hydration', {
+        startTime: performance.timeOrigin + beforeHydrationMeasure.startTime,
+        attributes: {
+          pathname: location.pathname,
+          query: location.search,
+        },
+      })
+      .end(
+        performance.timeOrigin +
+          hydrationMeasure.startTime +
+          hydrationMeasure.duration
+      )
+  }
 
   if (onPerfEntry) {
     performance.getEntriesByName('Next.js-hydration').forEach(onPerfEntry)