From f091d76dde83c733fffe2c9c862f4bcdc086a3c4 Mon Sep 17 00:00:00 2001
From: Alberto Leal <mail4alberto@gmail.com>
Date: Tue, 27 Oct 2020 16:19:44 -0400
Subject: [PATCH] feat(web-vitals): Capture extra information from LCP and CLS
 web vitals.

---
 packages/tracing/src/browser/metrics.ts       | 28 +++++++++++++++++--
 .../tracing/src/browser/web-vitals/getCLS.ts  | 11 +++++++-
 .../tracing/src/browser/web-vitals/getLCP.ts  | 15 ++++++++--
 3 files changed, 48 insertions(+), 6 deletions(-)

diff --git a/packages/tracing/src/browser/metrics.ts b/packages/tracing/src/browser/metrics.ts
index 00554fd02f6d..634b246a4301 100644
--- a/packages/tracing/src/browser/metrics.ts
+++ b/packages/tracing/src/browser/metrics.ts
@@ -1,14 +1,14 @@
 /* eslint-disable max-lines */
 /* eslint-disable @typescript-eslint/no-explicit-any */
 import { Measurements, SpanContext } from '@sentry/types';
-import { browserPerformanceTimeOrigin, getGlobalObject, logger } from '@sentry/utils';
+import { browserPerformanceTimeOrigin, getGlobalObject, htmlTreeAsString, logger } from '@sentry/utils';
 
 import { Span } from '../span';
 import { Transaction } from '../transaction';
 import { msToSec } from '../utils';
-import { getCLS } from './web-vitals/getCLS';
+import { getCLS, LayoutShift } from './web-vitals/getCLS';
 import { getFID } from './web-vitals/getFID';
-import { getLCP } from './web-vitals/getLCP';
+import { getLCP, LargestContentfulPaint } from './web-vitals/getLCP';
 import { getTTFB } from './web-vitals/getTTFB';
 import { getFirstHidden } from './web-vitals/lib/getFirstHidden';
 import { NavigatorDeviceMemory, NavigatorNetworkInformation } from './web-vitals/types';
@@ -20,6 +20,8 @@ export class MetricsInstrumentation {
   private _measurements: Measurements = {};
 
   private _performanceCursor: number = 0;
+  private _lcpEntry: LargestContentfulPaint | undefined;
+  private _clsEntry: LayoutShift | undefined;
 
   public constructor() {
     if (global && global.performance) {
@@ -135,6 +137,24 @@ export class MetricsInstrumentation {
     // Measurements are only available for pageload transactions
     if (transaction.op === 'pageload') {
       transaction.setMeasurements(this._measurements);
+
+      if (this._lcpEntry) {
+        logger.log('[Measurements] Adding LCP Data');
+        transaction.setTag('measurements.lcp.url', this._lcpEntry.url);
+        transaction.setData('measurements.lcp', {
+          size: this._lcpEntry.size,
+          id: this._lcpEntry.id,
+          url: this._lcpEntry.url,
+          element: this._lcpEntry.element ? htmlTreeAsString(this._lcpEntry.element) : undefined,
+        });
+      }
+
+      if (this._clsEntry) {
+        logger.log('[Measurements] Adding CLS Data');
+        transaction.setData('measurements.cls', {
+          sources: this._clsEntry.sources.map(source => htmlTreeAsString(source.node)),
+        });
+      }
     }
   }
 
@@ -149,6 +169,7 @@ export class MetricsInstrumentation {
 
       logger.log('[Measurements] Adding CLS');
       this._measurements['cls'] = { value: metric.value };
+      this._clsEntry = entry as LayoutShift;
     });
   }
 
@@ -206,6 +227,7 @@ export class MetricsInstrumentation {
       logger.log('[Measurements] Adding LCP');
       this._measurements['lcp'] = { value: metric.value };
       this._measurements['mark.lcp'] = { value: timeOrigin + startTime };
+      this._lcpEntry = entry as LargestContentfulPaint;
     });
   }
 
diff --git a/packages/tracing/src/browser/web-vitals/getCLS.ts b/packages/tracing/src/browser/web-vitals/getCLS.ts
index 530951834e47..eb3eed207a7d 100644
--- a/packages/tracing/src/browser/web-vitals/getCLS.ts
+++ b/packages/tracing/src/browser/web-vitals/getCLS.ts
@@ -21,9 +21,18 @@ import { onHidden } from './lib/onHidden';
 import { ReportHandler } from './types';
 
 // https://wicg.github.io/layout-instability/#sec-layout-shift
-interface LayoutShift extends PerformanceEntry {
+export interface LayoutShift extends PerformanceEntry {
   value: number;
   hadRecentInput: boolean;
+  lastInputTime: DOMHighResTimeStamp;
+  sources: Array<LayoutShiftAttribution>;
+  toJSON(): Record<string, unknown>;
+}
+
+export interface LayoutShiftAttribution {
+  node?: Node;
+  previousRect: DOMRectReadOnly;
+  currentRect: DOMRectReadOnly;
 }
 
 export const getCLS = (onReport: ReportHandler, reportAllChanges = false): void => {
diff --git a/packages/tracing/src/browser/web-vitals/getLCP.ts b/packages/tracing/src/browser/web-vitals/getLCP.ts
index e0fdd9c7cfde..0d0c5b3e670a 100644
--- a/packages/tracing/src/browser/web-vitals/getLCP.ts
+++ b/packages/tracing/src/browser/web-vitals/getLCP.ts
@@ -22,13 +22,24 @@ import { onHidden } from './lib/onHidden';
 import { whenInput } from './lib/whenInput';
 import { ReportHandler } from './types';
 
+// https://wicg.github.io/largest-contentful-paint/#sec-largest-contentful-paint-interface
+export interface LargestContentfulPaint extends PerformanceEntry {
+  renderTime: DOMHighResTimeStamp;
+  loadTime: DOMHighResTimeStamp;
+  size: number;
+  id: string;
+  url: string;
+  element?: Element;
+  toJSON(): Record<string, unknown>;
+}
+
 export const getLCP = (onReport: ReportHandler, reportAllChanges = false): void => {
   const metric = initMetric('LCP');
   const firstHidden = getFirstHidden();
 
   let report: ReturnType<typeof bindReporter>;
 
-  const entryHandler = (entry: PerformanceEntry): void => {
+  const entryHandler = (entry: LargestContentfulPaint): void => {
     // The startTime attribute returns the value of the renderTime if it is not 0,
     // and the value of the loadTime otherwise.
     const value = entry.startTime;
@@ -45,7 +56,7 @@ export const getLCP = (onReport: ReportHandler, reportAllChanges = false): void
     report();
   };
 
-  const po = observe('largest-contentful-paint', entryHandler);
+  const po = observe('largest-contentful-paint', entryHandler as PerformanceEntryHandler);
 
   if (po) {
     report = bindReporter(onReport, metric, po, reportAllChanges);