[lexical-markdown] Bug Fix: text left outside a markdown link keeps its format

[Om-singhaI]

Description

Importing *[h[ello](https://lexical.dev)* loses the italic on [h.

importRegExp matches here with a linkText of h[ello, which has more opening than closing brackets, so the LINK transformer splits it: ello goes inside the link and [h goes back as a sibling TextNode ahead of it. The link's own text node is given the format of the TextNode being replaced, but the sibling is a bare $createTextNode, so the format on that half is dropped. One italic run comes back as a plain [h next to an italic ello.

Both new nodes stand in for the same TextNode, so it's inconsistent for only one of them to keep its format. The rest of the import path already preserves it: importTextMatchTransformer hands replace a node that came out of splitText, and splitText copies format, style and detail onto every piece it makes. $createAutoLinkNode_ in @lexical/link gets it right for the same reason. The markdown LINK transformer is the one place that builds its leftover node by hand.

The fix reads the format once before the replace detaches the node, then applies it to both nodes.

I kept this to the format alone. The link's text node doesn't copy style or detail today either, so putting those on just the sibling would swap one mismatch for another.

Test plan

Added the italic case to the IMPORT_AND_EXPORT table right beside the existing [h[ello](...) split case, so it runs through import, export and the selection check. It needs an mdAfterExport because the exporter writes the italic as two runs, *[h*[*ello*](https://lexical.dev).

node_modules/.bin/vitest --project unit --no-watch run packages/lexical-markdown

Before

New test in place, MarkdownTransformers.ts still at main:

 × can import "*[h[ello](https://lexical.dev)*"

AssertionError: expected '<p><span style="white-space: pre-wrap…' to be '<p><i><em style="white-space: pre-wra…'

Expected: "<p><i><em style="white-space: pre-wrap;">[h</em></i><a href="https://lexical.dev"><i><em style="white-space: pre-wrap;">ello</em></i></a></p>"
Received: "<p><span style="white-space: pre-wrap;">[h</span><a href="https://lexical.dev"><i><em style="white-space: pre-wrap;">ello</em></i></a></p>"

 Test Files  1 failed | 6 passed (7)
      Tests  1 failed | 633 passed (634)

After

 Test Files  7 passed (7)
      Tests  634 passed (634)

packages/lexical-link stays green too, 10 files and 187 tests.

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Project	Deployment	Actions	Updated
lexical	Ready	Preview	Sep 8, 2026 12:47am UTC
lexical-playground	Ready	Preview	Sep 8, 2026 12:47am UTC

[potatowagon]

manually tested, lgtm

before:

after:

correct one: