fix(compiler-core): avoid crash on CDATA at the document root

[sarathfrancis90]

What kind of change does this PR introduce?

Bug fix.

Description

A CDATA section with no open element on the stack — e.g. at the document root — crashes the parser:

import { compile } from '@vue/compiler-dom'
compile('<![CDATA[x]]>')
// TypeError: Cannot read properties of undefined (reading 'ns')

oncdata reads stack[0].ns unconditionally, but stack[0] is undefined when there's no enclosing element. The same handler works inside an element (<div><![CDATA[x]]></div>), so this only affects top-level CDATA.

This falls back to the root namespace (currentOptions.ns) when the stack is empty — mirroring the existing onprocessinginstruction handler right below it — so top-level CDATA now reports CDATA_IN_HTML_CONTENT instead of throwing. Behavior inside elements and in SVG/foreign content is unchanged. Added a parser error-test case for the root position.

Summary by CodeRabbit

• Bug Fixes

  • Prevented a crash when encountering CDATA in certain parsing scenarios while preserving correct CDATA-in-HTML error reporting.

• Tests

  • Added coverage for root-level CDATA parsing to ensure the parser reports the expected error and remains stable.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: b7acb90b-8007-48ae-b8cd-d1ef16916cfd

📥 Commits

Reviewing files that changed from the base of the PR and between 7586305 and 3ab4554.

📒 Files selected for processing (1)

• packages/compiler-core/__tests__/parse.spec.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• packages/compiler-core/tests/parse.spec.ts

---

📝 Walkthrough

Walkthrough

Fixes a null-access in the compiler's CDATA handler by resolving namespace from the top of the element stack or falling back to options; adds a test asserting a root-level <![CDATA[cdata]]> reports CDATA_IN_HTML_CONTENT at document start.

Changes

CDATA root-level handling

Layer / File(s)	Summary
Parser null-safety fix packages/compiler-core/src/parser.ts	oncdata now reads namespace via a null-safe expression that uses stack[0].ns when present, otherwise currentOptions.ns.
Root-level CDATA test packages/compiler-core/__tests__/parse.spec.ts	Adds a CDATA_IN_HTML_CONTENT pattern for root-level <![CDATA[cdata]]>, asserting the error at offset 0 (line 1, column 1).

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 I nibbled a bug in the parser's root,
A CDATA alone with no enclosing boot,
A safe little fallback now keeps it fine,
No crash, just a test and a tidy line. 🌙

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title accurately describes the main fix: preventing a crash when CDATA appears at the document root by handling the empty stack case.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	106 kB	40.1 kB	36 kB
vue.global.prod.js	164 kB (+14 B)	60.1 kB (-3 B)	53.4 kB (-75 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	48.8 kB	19 kB	17.4 kB
createApp	56.9 kB	22 kB	20.1 kB
createSSRApp	61.2 kB	23.8 kB	21.7 kB
defineCustomElement	63.1 kB	23.9 kB	21.8 kB
overall	71.7 kB	27.4 kB	25 kB

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commit: 3ab4554

[edison1105]

/ecosystem-ci run

[vue-bot]

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