From cdf7f6937c6cc15a3b8ed63c080d7ecc0188f339 Mon Sep 17 00:00:00 2001
From: Seth Fowler <seth.fowler@datadoghq.com>
Date: Fri, 15 May 2026 11:16:53 +0100
Subject: [PATCH] =?UTF-8?q?=E2=99=BB=EF=B8=8F=20[PANA-7375]=20Eliminate=20?=
 =?UTF-8?q?unnecessary=20conditional=20node=20serialization?=
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---
 packages/rum-core/src/domain/privacy.ts       | 30 +++++++------------
 .../serialization/serializeMutations.ts       |  2 +-
 .../serialization/serializeNode.node.spec.ts  | 17 ++++-------
 .../record/serialization/serializeNode.ts     |  9 +++---
 4 files changed, 21 insertions(+), 37 deletions(-)

diff --git a/packages/rum-core/src/domain/privacy.ts b/packages/rum-core/src/domain/privacy.ts
index 7e79edf002..ae86cc7667 100644
--- a/packages/rum-core/src/domain/privacy.ts
+++ b/packages/rum-core/src/domain/privacy.ts
@@ -220,37 +220,23 @@ export function censorText(text: string): string {
   return text.replace(/\S/g, TEXT_MASKING_CHAR)
 }
 
-export function getTextContent(textNode: Node, parentNodePrivacyLevel: NodePrivacyLevel): string | undefined {
+export function getTextContent(textNode: Node, parentNodePrivacyLevel: NodePrivacyLevel): string {
   // The parent node may not be a html element which has a tagName attribute.
   // So just let it be undefined which is ok in this use case.
   const parentTagName = textNode.parentElement?.tagName
   let textContent = textNode.textContent || ''
-
-  const shouldIgnoreWhiteSpace = parentTagName === 'HEAD'
-  if (shouldIgnoreWhiteSpace && !textContent.trim()) {
-    return
-  }
-
   const nodePrivacyLevel = parentNodePrivacyLevel
 
-  const isScript = parentTagName === 'SCRIPT'
-
-  if (isScript) {
+  if (parentTagName === 'SCRIPT') {
     // For perf reasons, we don't record script (heuristic)
     textContent = CENSORED_STRING_MARK
   } else if (nodePrivacyLevel === NodePrivacyLevel.HIDDEN) {
     // Should never occur, but just in case, we set to CENSORED_MARK.
     textContent = CENSORED_STRING_MARK
   } else if (shouldMaskNode(textNode, nodePrivacyLevel)) {
-    if (
-      // Scrambling the child list breaks text nodes for DATALIST/SELECT/OPTGROUP
-      parentTagName === 'DATALIST' ||
-      parentTagName === 'SELECT' ||
-      parentTagName === 'OPTGROUP'
-    ) {
-      if (!textContent.trim()) {
-        return
-      }
+    if (parentTagName === 'DATALIST' || parentTagName === 'SELECT' || parentTagName === 'OPTGROUP') {
+      // Masking the child list breaks text nodes for DATALIST/SELECT/OPTGROUP.
+      // TODO: Reinvestigate this.
     } else if (parentTagName === 'OPTION') {
       // <Option> has low entropy in charset + text length, so use `CENSORED_STRING_MARK` when masked
       textContent = CENSORED_STRING_MARK
@@ -258,6 +244,12 @@ export function getTextContent(textNode: Node, parentNodePrivacyLevel: NodePriva
       textContent = censorText(textContent)
     }
   }
+
+  const shouldCollapseWhiteSpace = parentTagName === 'HEAD'
+  if (shouldCollapseWhiteSpace && !textContent.trim()) {
+    return ''
+  }
+
   return textContent
 }
 
diff --git a/packages/rum/src/domain/record/serialization/serializeMutations.ts b/packages/rum/src/domain/record/serialization/serializeMutations.ts
index 3f7eafba25..ba4a2018fb 100644
--- a/packages/rum/src/domain/record/serialization/serializeMutations.ts
+++ b/packages/rum/src/domain/record/serialization/serializeMutations.ts
@@ -214,7 +214,7 @@ function processCharacterDataMutations(
       continue // Mutations to this node should be ignored.
     }
 
-    const content = getTextContent(node, parentNodePrivacyLevel) ?? ''
+    const content = getTextContent(node, parentNodePrivacyLevel)
     transaction.setText(nodeId, content)
   }
 }
diff --git a/packages/rum/src/domain/record/serialization/serializeNode.node.spec.ts b/packages/rum/src/domain/record/serialization/serializeNode.node.spec.ts
index 3a1522883e..009aa497ea 100644
--- a/packages/rum/src/domain/record/serialization/serializeNode.node.spec.ts
+++ b/packages/rum/src/domain/record/serialization/serializeNode.node.spec.ts
@@ -101,15 +101,6 @@ describe('serializeNode for DOM nodes', () => {
       })
       expect(record?.data).toEqual([[ChangeType.AddNode, [null, '#text', '']]])
     })
-
-    it('does not serialize a whitespace-only node if the parent is a <head> element', async () => {
-      const record = await serializeHtml('<!doctype HTML><head>    </head>', {
-        input: 'document',
-        target: (node: Node) => (node as Document).head.firstChild!,
-        whitespace: 'keep',
-      })
-      expect(record?.data).toBeUndefined()
-    })
   })
 
   describe('for HTML elements', () => {
@@ -184,7 +175,7 @@ describe('serializeNode for DOM nodes', () => {
   })
 
   describe('for <head> elements', () => {
-    it('does not serialize whitespace', async () => {
+    it('serializes the element', async () => {
       const record = await serializeHtml('<!doctype HTML><head>  <title>  foo </title>  </head>', {
         input: 'document',
         whitespace: 'keep',
@@ -196,9 +187,11 @@ describe('serializeNode for DOM nodes', () => {
           [1, '#doctype', 'html', '', ''],
           [0, 'HTML'],
           [1, 'HEAD'],
-          [1, 'TITLE'],
+          [1, '#text', ''],
+          [0, 'TITLE'],
           [1, '#text', '  foo '],
-          [4, 'BODY'],
+          [4, '#text', ''],
+          [6, 'BODY'],
         ],
         [ChangeType.ScrollPosition, [0, 0, 0]],
       ])
diff --git a/packages/rum/src/domain/record/serialization/serializeNode.ts b/packages/rum/src/domain/record/serialization/serializeNode.ts
index fee673d60a..66cd43c4df 100644
--- a/packages/rum/src/domain/record/serialization/serializeNode.ts
+++ b/packages/rum/src/domain/record/serialization/serializeNode.ts
@@ -169,11 +169,8 @@ function serializeTextNode(
   privacyLevel: NodePrivacyLevel,
   transaction: SerializationTransaction
 ): void {
-  const textContent = getTextContent(textNode, privacyLevel)
-  if (textContent === undefined) {
-    return
-  }
   const { insertionPoint } = cursor.advance(textNode)
+  const textContent = getTextContent(textNode, privacyLevel)
   transaction.addNode(insertionPoint, '#text', textContent)
 }
 
@@ -192,7 +189,9 @@ function serializeHiddenNodePlaceholder(
   transaction: SerializationTransaction
 ): void {
   // We only generate placeholders for element nodes; other hidden nodes are simply not
-  // serialized.
+  // serialized. (But note that a non-element node can only be hidden if it's a descendant
+  // of another hidden node, since only element nodes can have a different privacy level
+  // than their parent.)
   if (!isElementNode(node)) {
     return
   }