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Fix markdown preview diff collapsing list items #335618

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Birarpanjot Singh Kanwer (arpankanwer) wants to merge 2 commits into
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Fix markdown preview diff collapsing list items #335618

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710dd98
fix: keep diff markers out of markdown list prefixes
arpankanwer Sep 11, 2026
0aa93ee
fix: cover blockquote and empty markers in diff list prefix
arpankanwer Sep 11, 2026
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13 changes: 12 additions & 1 deletion extensions/markdown-language-features/src/preview/documentRenderer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -277,6 +277,12 @@ export class MdDocumentRenderer {
}
}

/** Length of the leading list marker (`- `, `1. `) that must stay intact for list parsing. */
function getListMarkerPrefixLength(line: string): number {
const match = /^[ \t]*(?:>[ \t]*)*(?:[-*+]|\d+[.)])(?:[ \t]+|$)/.exec(line);
return match ? match[0].length : 0;
}

/**
* Injects empty marker `<span>` elements into the markdown source text at inner change positions.
*/
Expand All @@ -301,13 +307,18 @@ function injectInnerChangeMarkers(text: string, innerChanges: readonly MarkdownP
}

let line = lines[lineNum];
const listPrefixLength = getListMarkerPrefixLength(line);

// Sort by startColumn descending so that insertions don't shift earlier positions
changes.sort((a, b) => b.change.startColumn - a.change.startColumn);

for (const { index, change } of changes) {
const start = Math.min(change.startColumn, line.length);
let start = Math.min(change.startColumn, line.length);
const end = Math.min(change.endColumn, line.length);
// Keep the highlight out of the list marker so the line still parses as a list item.
if (start < listPrefixLength) {
start = listPrefixLength;
}
if (start >= end) {
continue;
}
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