fix: prevent iframe content from being cloned twice

actions-user · claude · actions-user · commit 9d648f1e0fbe · 2026-03-16T15:00:18.000+08:00
cloneIFrameElement (called via cloneSingleNode) already recursively clones the entire iframe contentDocument.body. The subsequent call to cloneChildren was then also iterating contentDocument.body.childNodes and appending them again, duplicating every child element. Fix: return early from cloneChildren when the native node is an iframe, since its subtree is fully handled by cloneIFrameElement. Closes #543 Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
diff --git a/src/clone-node.ts b/src/clone-node.ts
@@ -104,11 +104,11 @@ async function cloneChildren<T extends HTMLElement>(
 
   if (isSlotElement(nativeNode) && nativeNode.assignedNodes) {
     children = toArray<T>(nativeNode.assignedNodes())
-  } else if (
-    isInstanceOfElement(nativeNode, HTMLIFrameElement) &&
-    nativeNode.contentDocument?.body
-  ) {
-    children = toArray<T>(nativeNode.contentDocument.body.childNodes)
+  } else if (isInstanceOfElement(nativeNode, HTMLIFrameElement)) {
+    // cloneIFrameElement (called by cloneSingleNode) already recursively clones
+    // the iframe's contentDocument.body and all its descendants.
+    // Appending children here would duplicate the iframe content.
+    return clonedNode
   } else {
     children = toArray<T>((nativeNode.shadowRoot ?? nativeNode).childNodes)
   }
diff --git a/test/resources/iframe-content/node.html b/test/resources/iframe-content/node.html
@@ -0,0 +1,7 @@
+<div id="iframe-wrapper" style="width:200px;height:80px;">
+  <iframe
+    id="test-iframe"
+    style="width:100%;height:100%;border:none;"
+    srcdoc="<html><body><p class='iframe-para' data-testid='iframe-para'>IFRAME_CONTENT</p></body></html>"
+  ></iframe>
+</div>
diff --git a/test/spec/special.spec.ts b/test/spec/special.spec.ts
@@ -2,6 +2,7 @@
 
 import '../spec/setup'
 import { toPng } from '../../src'
+import { cloneNode } from '../../src/clone-node'
 import { delay } from '../../src/util'
 import { assertTextRendered, bootstrap, renderAndCheck } from '../spec/helper'
 
@@ -59,4 +60,41 @@ describe('special cases', () => {
       .then(done)
       .catch(done)
   })
+
+  it('should not duplicate iframe content when cloning', (done) => {
+    // Regression test for: cloneChildren() re-appended iframe body childNodes
+    // after cloneSingleNode() → cloneIFrameElement() had already recursively
+    // cloned the full iframe body, causing every child to appear twice.
+    bootstrap('iframe-content/node.html')
+      .then((node) => {
+        const iframe = node.querySelector('iframe') as HTMLIFrameElement
+        // Poll until srcdoc iframe body is accessible (async load)
+        return new Promise<HTMLDivElement>((resolve, reject) => {
+          let attempts = 0
+          const poll = () => {
+            attempts++
+            const ready =
+              iframe.contentDocument?.body?.querySelector('.iframe-para')
+            if (ready) {
+              resolve(node)
+            } else if (attempts > 30) {
+              reject(new Error('iframe did not load in time'))
+            } else {
+              setTimeout(poll, 100)
+            }
+          }
+          poll()
+        })
+      })
+      .then((node) => cloneNode(node, {}, true))
+      .then((clonedNode) => {
+        expect(clonedNode).not.toBeNull()
+        // With the bug: two .iframe-para elements appear (duplicate children).
+        // With the fix: exactly one .iframe-para appears.
+        const paras = clonedNode!.querySelectorAll('.iframe-para')
+        expect(paras.length).toBe(1)
+      })
+      .then(done)
+      .catch(done)
+  })
 })
