fix: handle setBitOr in ListBasicTreeViewDU.sliceTo()

packages/ssz/src/viewDU/listBasic.ts

@@ -60,11 +60,14 @@ export class ListBasicTreeViewDU<ElementType extends BasicType<unknown>> extends
     const chunkIndex = Math.floor(index / this.type.itemsPerChunk);
     const nodePrev = (this.nodes[chunkIndex] ?? getNodeAtDepth(rootNode, this.type.depth, chunkIndex)) as LeafNode;
 
-    const nodeChanged = nodePrev.clone();
-    // set remaining items in the same chunk to 0
-    for (let i = index + 1; i < (chunkIndex + 1) * this.type.itemsPerChunk; i++) {
-      this.type.elementType.tree_setToPackedNode(nodeChanged, i, 0);
+    // we can't set remaining items in the same chunk to 0 with tree_setToPackedNode api due to setBitwiseOR in UintNumberType
+    // instead, we set the same value in nodePrev up until index
+    const nodeChanged = LeafNode.fromZero();
+    for (let i = chunkIndex * this.type.itemsPerChunk; i <= index; i++) {
+      const prevValue = this.type.elementType.tree_getFromPackedNode(nodePrev, i);
+      this.type.elementType.tree_setToPackedNode(nodeChanged, i, prevValue);
     }
+
     const chunksNode = this.type.tree_getChunksNode(this._rootNode);
     let newChunksNode = setNodesAtDepth(chunksNode, this.type.chunkDepth, [chunkIndex], [nodeChanged]);
     // also do the treeZeroAfterIndex operation on the chunks tree

packages/ssz/test/unit/byType/listBasic/tree.test.ts

@@ -212,24 +212,26 @@ describe("ListBasicType drop caches", () => {
 });
 
 describe("ListBasicType.sliceTo", () => {
-  // same to BeaconState InactivityScores
-  it("Slice List at multiple length", () => {
-    const listType = new ListBasicType(new UintNumberType(8), 100);
-    const listView = listType.defaultViewDU();
-    const listRoots: string[] = [];
-    const listSerialized: string[] = [];
-
-    for (let i = 0; i < 16; i++) {
-      listView.push(i);
-      listSerialized[i] = toHexString(listView.serialize());
-      listRoots[i] = toHexString(listView.hashTreeRoot());
-    }
-
-    for (let i = 0; i < 16; i++) {
-      const listSlice = listView.sliceTo(i);
-      expect(listSlice.length).to.equal(i + 1, `Wrong length at .sliceTo(${i})`);
-      expect(toHexString(listSlice.serialize())).equals(listSerialized[i], `Wrong serialize at .sliceTo(${i})`);
-      expect(toHexString(listSlice.hashTreeRoot())).equals(listRoots[i], `Wrong root at .sliceTo(${i})`);
-    }
-  });
+  // same to BeaconState inactivityScores and previousEpochParticipation
+  for (const elementType of [new UintNumberType(8), new UintNumberType(1, {setBitwiseOR: true})]) {
+    it(`Slice list of ${elementType.typeName} at multiple length`, () => {
+      const listType = new ListBasicType(elementType, 100);
+      const listView = listType.defaultViewDU();
+      const listRoots: string[] = [];
+      const listSerialized: string[] = [];
+
+      for (let i = 0; i < 16; i++) {
+        listView.push(i);
+        listSerialized[i] = toHexString(listView.serialize());
+        listRoots[i] = toHexString(listView.hashTreeRoot());
+      }
+
+      for (let i = 0; i < 16; i++) {
+        const listSlice = listView.sliceTo(i);
+        expect(listSlice.length).to.equal(i + 1, `Wrong length at .sliceTo(${i})`);
+        expect(toHexString(listSlice.serialize())).equals(listSerialized[i], `Wrong serialize at .sliceTo(${i})`);
+        expect(toHexString(listSlice.hashTreeRoot())).equals(listRoots[i], `Wrong root at .sliceTo(${i})`);
+      }
+    });
+  }
 });