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ref(browser-utils): Align standalone LCP span attribute setting with pageload span LCP attributes #16844

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Merged
merged 3 commits into from
Jul 9, 2025
Merged

ref(browser-utils): Align standalone LCP span attribute setting with pageload span LCP attributes #16844

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8008d2b
ref(browser-utils): Align standalone LCP span attribute setting with …
Lms24 Jul 8, 2025
84630a3
fix size
Lms24 Jul 8, 2025
9d48700
fix integration, add unit test
Lms24 Jul 8, 2025
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1 change: 0 additions & 1 deletion .../browser-integration-tests/suites/tracing/metrics/web-vitals-lcp-standalone-spans/test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,6 @@ sentryTest('captures LCP vital as a standalone span', async ({ getLocalTestUrl,
'user_agent.original': expect.stringContaining('Chrome'),
'sentry.pageload.span_id': expect.stringMatching(/[a-f0-9]{16}/),
'lcp.element': 'body > img',
'lcp.id': '',
'lcp.loadTime': expect.any(Number),
'lcp.renderTime': expect.any(Number),
'lcp.size': expect.any(Number),
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32 changes: 24 additions & 8 deletions packages/browser-utils/src/metrics/lcp.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,7 @@ export function trackLcpAsStandaloneSpan(): void {
}
sentSpan = true;
if (pageloadSpanId) {
sendStandaloneLcpSpan(standaloneLcpValue, standaloneLcpEntry, pageloadSpanId);
_sendStandaloneLcpSpan(standaloneLcpValue, standaloneLcpEntry, pageloadSpanId);
}
cleanupLcpHandler();
}
Expand Down Expand Up @@ -88,7 +88,14 @@ export function trackLcpAsStandaloneSpan(): void {
}, 0);
}

function sendStandaloneLcpSpan(lcpValue: number, entry: LargestContentfulPaint | undefined, pageloadSpanId: string) {
/**
* Exported only for testing!
*/
export function _sendStandaloneLcpSpan(
lcpValue: number,
entry: LargestContentfulPaint | undefined,
pageloadSpanId: string,
) {
DEBUG_BUILD && logger.log(`Sending LCP span (${lcpValue})`);

const startTime = msToSec((browserPerformanceTimeOrigin() || 0) + (entry?.startTime || 0));
Expand All @@ -105,12 +112,21 @@ function sendStandaloneLcpSpan(lcpValue: number, entry: LargestContentfulPaint |
};

if (entry) {
attributes['lcp.element'] = htmlTreeAsString(entry.element);
attributes['lcp.id'] = entry.id;
attributes['lcp.url'] = entry.url;
attributes['lcp.loadTime'] = entry.loadTime;
attributes['lcp.renderTime'] = entry.renderTime;
attributes['lcp.size'] = entry.size;
entry.element && (attributes['lcp.element'] = htmlTreeAsString(entry.element));
entry.id && (attributes['lcp.id'] = entry.id);

// Trim URL to the first 200 characters.
entry.url && (attributes['lcp.url'] = entry.url.trim().slice(0, 200));

// loadTime is the time of LCP that's related to receiving the LCP element response..
entry.loadTime != null && (attributes['lcp.loadTime'] = entry.loadTime);

// renderTime is loadTime + rendering time
// it's 0 if the LCP element is loaded from a 3rd party origin that doesn't send the
// `Timing-Allow-Origin` header.
entry.renderTime != null && (attributes['lcp.renderTime'] = entry.renderTime);

entry.size != null && (attributes['lcp.size'] = entry.size);
}

const span = startStandaloneWebVitalSpan({
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