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GoogleChrome · Dec 7, 2023 · fae4882 · fae4882
1 parent cd40c14
commit fae4882
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Showing 2 changed files with 76 additions and 6 deletions.
diff --git a/core/computed/metrics/cumulative-layout-shift.js b/core/computed/metrics/cumulative-layout-shift.js
@@ -87,18 +87,14 @@ class CumulativeLayoutShift {
     const impactByNodeId = new Map();
 
     for (const event of layoutShiftEvents) {
-      if (!event || !event.impactedNodes) {
-        continue;
-      }
+      if (!event.impactedNodes) continue;
 
       let totalAreaOfImpact = 0;
       /** @type {Map<number, number>} */
       const pixelsMovedPerNode = new Map();
 
       for (const node of event.impactedNodes) {
-        if (!node.node_id || !node.old_rect || !node.new_rect) {
-          continue;
-        }
+        if (!node.node_id || !node.old_rect || !node.new_rect) continue;
 
         const oldRect = RectHelpers.traceRectToLHRect(node.old_rect);
         const newRect = RectHelpers.traceRectToLHRect(node.new_rect);

diff --git a/core/test/computed/metrics/cumulative-layout-shift-test.js b/core/test/computed/metrics/cumulative-layout-shift-test.js
@@ -492,5 +492,79 @@ describe('Metrics: CLS', () => {
         [25, 0.6],
       ]);
     });
+
+    it('ignores events with no impacted nodes', () => {
+      const layoutShiftEvents = [
+        {
+          ts: 1_000_000,
+          isMainFrame: true,
+          weightedScore: 1,
+          impactedNodes: [
+            {
+              new_rect: [0, 0, 200, 200],
+              node_id: 60,
+              old_rect: [0, 0, 200, 100],
+            },
+            {
+              new_rect: [0, 300, 200, 200],
+              node_id: 25,
+              old_rect: [0, 100, 200, 100],
+            },
+          ],
+        },
+        {
+          ts: 2_000_000,
+          isMainFrame: true,
+          weightedScore: 0.3,
+        },
+      ];
+
+      const impactByNodeId = CumulativeLayoutShift.getImpactByNodeId(layoutShiftEvents);
+      expect(Array.from(impactByNodeId.entries())).toEqual([
+        [60, 0.4],
+        [25, 0.6],
+      ]);
+    });
+
+    it('ignores malformed impacted nodes', () => {
+      const layoutShiftEvents = [
+        {
+          ts: 1_000_000,
+          isMainFrame: true,
+          weightedScore: 1,
+          impactedNodes: [
+            {
+              // Malformed, no old_rect
+              // Entire weightedScore is therefore attributed to node_id 25
+              new_rect: [0, 0, 200, 200],
+              node_id: 60,
+            },
+            {
+              new_rect: [0, 300, 200, 200],
+              node_id: 25,
+              old_rect: [0, 100, 200, 100],
+            },
+          ],
+        },
+        {
+          ts: 2_000_000,
+          isMainFrame: true,
+          weightedScore: 0.3,
+          impactedNodes: [
+            {
+              new_rect: [0, 100, 200, 200],
+              node_id: 60,
+              old_rect: [0, 0, 200, 200],
+            },
+          ],
+        },
+      ];
+
+      const impactByNodeId = CumulativeLayoutShift.getImpactByNodeId(layoutShiftEvents);
+      expect(Array.from(impactByNodeId.entries())).toEqual([
+        [25, 1],
+        [60, 0.3],
+      ]);
+    });
   });
 });