From 588d002352dc0a03321c7628f7ac41b0358618e0 Mon Sep 17 00:00:00 2001
From: jaj1014 <ajax@pendo.io>
Date: Mon, 20 Nov 2023 11:56:25 -0500
Subject: [PATCH] fix: inserted styles lost when moving elements

---
 packages/rrdom/src/index.ts             | 25 +++++++++++++++++++
 packages/rrdom/test/virtual-dom.test.ts | 32 +++++++++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/packages/rrdom/src/index.ts b/packages/rrdom/src/index.ts
index eeddb03e1c..df0b9bf4b0 100644
--- a/packages/rrdom/src/index.ts
+++ b/packages/rrdom/src/index.ts
@@ -15,6 +15,7 @@ import type {
   styleSheetRuleData,
   styleDeclarationData,
 } from '@rrweb/types';
+import { IncrementalSource } from '@rrweb/types';
 import {
   BaseRRNode as RRNode,
   BaseRRCDATASectionImpl,
@@ -248,6 +249,30 @@ export function buildFromNode(
       for (const { name, value } of Array.from(elementNode.attributes)) {
         rrElement.attributes[name] = value;
       }
+
+      // CSSRules inserted by earlier mutations can be dropped if diff'ing
+      // results in the style element's position in the DOM changing
+      // since inserted rules are not persisted with the element to it's new location
+      if (tagName === 'STYLE') {
+        const cssElementNode = elementNode as HTMLStyleElement;
+
+        if (cssElementNode.sheet?.cssRules.length) {
+          const cssRules = cssElementNode.sheet.cssRules;
+
+          for (let i = 0; i < cssRules.length; i++) {
+            (rrNode as RRStyleElement).rules.push({
+              source: IncrementalSource.StyleSheetRule,
+              adds: [
+                {
+                  index: i,
+                  rule: cssRules[i].cssText,
+                },
+              ],
+            });
+          }
+        }
+      }
+
       elementNode.scrollLeft && (rrElement.scrollLeft = elementNode.scrollLeft);
       elementNode.scrollTop && (rrElement.scrollTop = elementNode.scrollTop);
       /**
diff --git a/packages/rrdom/test/virtual-dom.test.ts b/packages/rrdom/test/virtual-dom.test.ts
index b99aca5ae4..3677cb1067 100644
--- a/packages/rrdom/test/virtual-dom.test.ts
+++ b/packages/rrdom/test/virtual-dom.test.ts
@@ -24,6 +24,7 @@ import {
   RRCanvasElement,
   RRDocument,
   RRElement,
+  RRStyleElement,
   BaseRRNode as RRNode,
 } from '../src';
 import { compileTSCode } from './utils';
@@ -207,6 +208,37 @@ describe('RRDocument for browser environment', () => {
       expect((rrNode as RRElement).tagName).toEqual('SHADOWROOT');
       expect(rrNode).toBe(parentRRNode.shadowRoot);
     });
+
+    it('can copy CSSRules for style elements to RRNode', () => {
+      const styleElement = document.createElement('style') as HTMLStyleElement;
+      styleElement.innerHTML =
+        '.new-element-class {font-size: 32px; color: tomato;}';
+      document.body.appendChild(styleElement);
+      styleElement.sheet?.insertRule(
+        '.target-element {background-color: teal;}',
+      );
+      const rrdom = new RRDocument();
+
+      let rrNode = buildFromNode(styleElement, rrdom, mirror);
+
+      expect((rrNode as RRStyleElement).rules).toEqual([
+        {
+          adds: [
+            { index: 0, rule: '.target-element {background-color: teal;}' },
+          ],
+          source: 8,
+        },
+        {
+          adds: [
+            {
+              index: 1,
+              rule: '.new-element-class {font-size: 32px; color: tomato;}',
+            },
+          ],
+          source: 8,
+        },
+      ]);
+    });
   });
 
   describe('create a RRDocument from a html document', () => {