update

core/audits/server-response-time.js

@@ -17,8 +17,6 @@ const UIStrings = {
   description: 'Keep the server response time for the main document short because all other requests depend on it. [Learn more about the Time to First Byte metric](https://developer.chrome.com/docs/lighthouse/performance/time-to-first-byte/).',
   /** Used to summarize the total Server Response Time duration for the primary HTML response. The `{timeInMs}` placeholder will be replaced with the time duration, shown in milliseconds (e.g. 210 ms) */
   displayValue: `Root document took {timeInMs, number, milliseconds}\xa0ms`,
-  /** A message displayed in a Lighthouse audit result warning that the server response time could not be determined. */
-  missingTimingWarning: 'Missing timing information needed to determine the server response time',
 };
 
 const str_ = i18n.createIcuMessageFn(import.meta.url, UIStrings);
@@ -49,7 +47,7 @@ class ServerResponseTime extends Audit {
    */
   static calculateResponseTime(record) {
     // Lightrider does not have timings for sendEnd, but we do have this timing which should be
-    // close.
+    // close to the response time.
     if (global.isLightrider && record.lrStatistics) return record.lrStatistics.requestMs;
 
     if (!record.timing) return null;
@@ -69,11 +67,7 @@ class ServerResponseTime extends Audit {
 
     const responseTime = ServerResponseTime.calculateResponseTime(mainResource);
     if (responseTime === null) {
-      return {
-        score: 0,
-        runWarnings: [str_(UIStrings.missingTimingWarning)],
-        notApplicable: true,
-      };
+      throw new Error('no timing found for main resource');
     }
 
     const passed = responseTime < TOO_SLOW_THRESHOLD_MS;