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fix(web-vitals): Only report FCP or FP if the page wasn't hidden prior to their instrumentation #2979

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Merged
merged 1 commit into from
Oct 19, 2020
Merged

fix(web-vitals): Only report FCP or FP if the page wasn't hidden prior to their instrumentation #2979

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9 changes: 7 additions & 2 deletions packages/tracing/src/browser/metrics.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ import { getCLS } from './web-vitals/getCLS';
import { getFID } from './web-vitals/getFID';
import { getLCP } from './web-vitals/getLCP';
import { getTTFB } from './web-vitals/getTTFB';
import { getFirstHidden } from './web-vitals/lib/getFirstHidden';

const global = getGlobalObject<Window>();

Expand Down Expand Up @@ -85,13 +86,17 @@ export class MetricsInstrumentation {

// capture web vitals

if (entry.name === 'first-paint') {
const firstHidden = getFirstHidden();
// Only report if the page wasn't hidden prior to the web vital.
const shouldRecord = entry.startTime < firstHidden.timeStamp;

if (entry.name === 'first-paint' && shouldRecord) {
logger.log('[Measurements] Adding FP');
this._measurements['fp'] = { value: entry.startTime };
this._measurements['mark.fp'] = { value: startTimestamp };
}

if (entry.name === 'first-contentful-paint') {
if (entry.name === 'first-contentful-paint' && shouldRecord) {
logger.log('[Measurements] Adding FCP');
this._measurements['fcp'] = { value: entry.startTime };
this._measurements['mark.fcp'] = { value: startTimestamp };
Expand Down