INP breakdown and LoAF integration with web-vitals v4

package.json

@@ -1,6 +1,6 @@
 {
   "name": "web-vitals-extension",
-  "version": "1.4.2",
+  "version": "1.5.0",
   "description": "Instant Web Vitals metrics",
   "main": "src/browser_action/vitals.js",
   "repository": "https://github.com/googlechrome/web-vitals-extension",
@@ -21,6 +21,6 @@
     "eslint-config-google": "^0.14.0"
   },
   "dependencies": {
-    "web-vitals": "^3.5.2"
+    "web-vitals": "^4.0.0"
   }
 }

src/browser_action/on-each-interaction.js

@@ -13,17 +13,44 @@
 
 import {INPThresholds} from './web-vitals.js';
 
-
 /**
  * @param {Function} callback
  */
 export function onEachInteraction(callback) {
   const valueToRating = (score) => score <= INPThresholds[0] ? 'good' : score <= INPThresholds[1] ? 'needs-improvement' : 'poor';
 
-  const observer = new PerformanceObserver((list) => {
+  const eventObserver = new PerformanceObserver((list) => {
+    const entries = list.getEntries();
     const interactions = {};
 
-    for (const entry of list.getEntries().filter((entry) => entry.interactionId)) {
+    const getSelector = (node, maxLen) => {
+      let sel = '';
+
+      try {
+        while (node && node.nodeType !== 9) {
+          const el = node;
+          const part = el.id
+            ? '#' + el.id
+            : getName(el) +
+              (el.classList &&
+              el.classList.value &&
+              el.classList.value.trim() &&
+              el.classList.value.trim().length
+                ? '.' + el.classList.value.trim().replace(/\s+/g, '.')
+                : '');
+          if (sel.length + part.length > (maxLen || 100) - 1) return sel || part;
+          sel = sel ? part + '>' + sel : part;
+          if (el.id) break;
+          node = el.parentNode;
+        }
+      } catch (err) {
+        // Do nothing...
+      }
+      return sel;
+    };
+
+    // Filter all events to those with interactionids
+    for (const entry of entries.filter((entry) => entry.interactionId)) {
       interactions[entry.interactionId] = interactions[entry.interactionId] || [];
       interactions[entry.interactionId].push(entry);
     }
@@ -33,12 +60,24 @@ export function onEachInteraction(callback) {
     for (const interaction of Object.values(interactions)) {
       const entry = interaction.reduce((prev, curr) => prev.duration >= curr.duration ? prev : curr);
       const value = entry.duration;
+      const interactionId = entry.interactionId;
+
+      // Filter down LoAFs to ones that intersected any event startTime and any processingEnd
+      const longAnimationFrameEntries = getIntersectingLoAFs(entry.startTime, entry.startTime + entry.value)
+
+      let firstEntryWithTarget = interaction[0].target;
+      firstEntryWithTarget = null;
+      if (!firstEntryWithTarget) {
+        firstEntryWithTarget = Object.values(interactions).flat().find(entry => entry.interactionId === interactionId && entry.target)?.target;
+      }
 
       callback({
         attribution: {
-          eventEntry: entry,
-          eventTime: entry.startTime,
-          eventType: entry.name,
+          interactionTarget: getSelector(firstEntryWithTarget),
+          interactionTargetElement: firstEntryWithTarget,
+          interactionTime: entry.startTime,
+          interactionType: entry.name.startsWith('key') ? 'keyboard' : 'pointer',
+          longAnimationFrameEntries: longAnimationFrameEntries
         },
         entries: interaction,
         name: 'Interaction',
@@ -48,9 +87,39 @@ export function onEachInteraction(callback) {
     }
   });
 
-  observer.observe({
+  eventObserver.observe({
     type: 'event',
     durationThreshold: 0,
     buffered: true,
   });
+
+  let recentLoAFs = [];
+
+  const getIntersectingLoAFs = (start, end) => {
+    const intersectingLoAFs = [];
+
+    for (let i = 0, loaf; (loaf = recentLoAFs[i]); i++) {
+      // If the LoAF ends before the given start time, ignore it.
+      if (loaf.startTime + loaf.duration < start) continue;
+
+      // If the LoAF starts after the given end time, ignore it and all
+      // subsequent pending LoAFs (because they're in time order).
+      if (loaf.startTime > end) break;
+
+      // Still here? If so this LoAF intersects with the interaction.
+      intersectingLoAFs.push(loaf);
+    }
+    return intersectingLoAFs;
+  };
+
+  const loafObserver = new PerformanceObserver((list) => {
+    // We report interactions immediately, so don't need to keep many LoAFs around.
+    // Let's keep the last 5.
+    recentLoAFs = recentLoAFs.concat(list.getEntries()).slice(-5);
+
+  });
+  loafObserver.observe({
+    type: 'long-animation-frame',
+    buffered: true,
+  });
 }