From 67567d402da7576fde8f6ae25282373656b7e61e Mon Sep 17 00:00:00 2001
From: Damian Pieczynski <piecyk@gmail.com>
Date: Mon, 27 Feb 2023 11:57:22 +0100
Subject: [PATCH] feat: add elementKeyAttribute, controls element cache

---
 packages/virtual-core/src/index.ts | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/packages/virtual-core/src/index.ts b/packages/virtual-core/src/index.ts
index 4786e5182..dcc2a9cb2 100644
--- a/packages/virtual-core/src/index.ts
+++ b/packages/virtual-core/src/index.ts
@@ -259,6 +259,7 @@ export interface VirtualizerOptions<
   rangeExtractor?: (range: Range) => number[]
   scrollMargin?: number
   scrollingDelay?: number
+  elementKeyAttribute?: string
   indexAttribute?: string
   initialMeasurementsCache?: VirtualItem[]
 }
@@ -344,6 +345,7 @@ export class Virtualizer<
       scrollMargin: 0,
       scrollingDelay: 150,
       indexAttribute: 'data-index',
+      elementKeyAttribute: 'data-element-key',
       initialMeasurementsCache: [],
       ...opts,
     }
@@ -561,17 +563,17 @@ export class Virtualizer<
   ) => {
     const index = this.indexFromElement(node)
 
-    const item = this.measurementsCache[index]
-    if (!item) {
-      return
-    }
+    const item = notUndefined(this.measurementsCache[index])
+
+    const elementKey =
+      node.getAttribute(this.options.elementKeyAttribute) ?? item.key
 
-    const prevNode = this.measureElementCache.get(item.key)
+    const prevNode = this.measureElementCache.get(elementKey)
 
     if (!node.isConnected) {
       this.observer.unobserve(node)
       if (node === prevNode) {
-        this.measureElementCache.delete(item.key)
+        this.measureElementCache.delete(elementKey)
       }
       return
     }
@@ -581,7 +583,7 @@ export class Virtualizer<
         this.observer.unobserve(prevNode)
       }
       this.observer.observe(node)
-      this.measureElementCache.set(item.key, node)
+      this.measureElementCache.set(elementKey, node)
     }
 
     const measuredItemSize = this.options.measureElement(node, entry, this)