allowedTags: a self-closing custom tag at the end of a line turns every later blank line into `<!---->` (preprocessCustomTags)

Aperta
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Dal 29/10/2026.

  • #708 di @ahmedriad1 — aperta

Valutazione

Difficoltà
3/5
Tempo stimato
1-2 giorni
Idoneità per principianti
72/100
Tipo di issue
Bug
Chiarezza
Specificata chiaramente
Stato di attività
Attiva
Stack tecnologico
markdown, react, typescript
Ambito
frontend

Direzione di ricerca

Start in lib/preprocess-custom-tags.ts with normalizeUnclosedOpenTags, then compare its handling of self-closing tags with countNonSelfClosingOpenTags in parse-blocks.tsx. Reproduce both examples from the issue and check that self-closing tags no longer split later lists or corrupt blank lines, while an inline tag with a soft line break stays within one paragraph.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

Version

streamdown 2.7.1. The same code is on main (ec1489a). 2.5.0 is not affected.

Repro
<Streamdown allowedTags={{ "cite-ref": ["id"] }} mode="static">
  {'Intro <cite-ref id="a" />\n\n- one\n\n- two\n\nLast'}
</Streamdown>

2.7.1 output (classes stripped):

<p>Intro <cite-ref id="a"></cite-ref></p>
<ul><li>one</li></ul>
<ul><li>two</li></ul>
<p>Last</p>

Expected (2.5.0, or 2.7.1 without allowedTags): one <ul> with both items.

Effects

After the first self-closing allowed tag that ends a line:

  • Loose lists split into one <ul>/<ol> per item.
  • Lists flip between tight and loose.
  • On 2.7.1, a later fenced code block with a blank line shows a literal <!----> line. #684 fixes this one on main.

In our app, 19 of 75 real LLM answers end a line with <citation ids="…" />. 11 of them render differently.

Cause

In lib/preprocess-custom-tags.ts, normalizeUnclosedOpenTags matches open tags with <(${tagName})(?=[\s>/])([^>]*)>. That pattern also matches <tag … />. A self-closing tag has no </tag>, so it is treated as an unclosed (streaming) container. If the next character is \n, the function inserts \n\n and replaces every later blank line in the document with <!---->, then stops.

parse-blocks.tsx already skips self-closing tags in countNonSelfClosingOpenTags.

Related, an inline tag whose body has a soft line break
<Streamdown allowedTags={{ verse: [] }} mode="static">
  {"He said: <verse>line one\nline two</verse> and left."}
</Streamdown>

2.7.1 output:

<p>He said: <verse></verse></p>
<p>line one
line two</p>
<p>and left.</p>

The tag is emptied and its body becomes a separate paragraph. In 2.5.0 the body stayed inside the tag within one paragraph. The cause is that normalizeClosedTag now pads any body that contains \n (since #484), even when the tag is inline.

Suggested fix
  1. In normalizeUnclosedOpenTags, skip matches whose open tag ends with />, in the same way countNonSelfClosingOpenTags does.
  2. Only apply the blank-line sandwich when the open tag starts a line, or when the body contains a blank line. Leave inline tags whose body only has soft line breaks alone.
  3. Consider an opt-out so allowedTags can only extend the sanitize schema, as it did up to 2.5. For example customTagMarkdown={false}, or a per-tag setting.

Our workaround: pass the tags through rehypePlugins (built from defaultRehypePlugins with an extended sanitize schema) instead of allowedTags.

We can open a PR with tests for the two cases above.

Lingua principale
TypeScript
Stelle
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Fork
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Merge medio
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PR unite (30g)
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