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fix(react): prevent intra-word _ from rendering as emphasis in composer #1375

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fix(react): prevent intra-word _ from rendering as emphasis in composer #1375

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bd8a429
fix(react): prevent intra-word _ and * from rendering as emphasis
rahulnits-sketch Sep 25, 2026
f162c12
fix(react): restrict intra-word check to underscore and scan subseque…
rahulnits-sketch Oct 4, 2026
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29 changes: 28 additions & 1 deletion packages/react/src/lib/contentEditableComposer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,30 @@ const findLink = (text, start) => {
};
};

const isAlphanumeric = (ch) => Boolean(ch && /[a-zA-Z0-9]/.test(ch));
const isWhitespace = (ch) => Boolean(ch && /\s/.test(ch));

const isValidEmphasis = (marker, text, start, end) => {
if (marker === '`' || marker === '~~') {
return true;
}
const prevChar = start > 0 ? text[start - 1] : '';
const firstInside = text[start + marker.length];
const lastInside = text[end - 1];
const nextChar =
end + marker.length < text.length ? text[end + marker.length] : '';

if (isWhitespace(firstInside) || isWhitespace(lastInside)) return false;

// CommonMark: only underscore delimiters cannot be intra-word
if (marker === '_' || marker === '__') {
if (isAlphanumeric(prevChar)) return false;
if (isAlphanumeric(nextChar)) return false;
}

return true;
};

const appendMarkdown = (parent, text) => {
const tokens = [
['**', 'strong'],
Expand Down Expand Up @@ -91,7 +115,10 @@ const appendMarkdown = (parent, text) => {

if (token) {
const [marker, tagName] = token;
const end = text.indexOf(marker, index + marker.length);
let end = text.indexOf(marker, index + marker.length);
while (end !== -1 && !isValidEmphasis(marker, text, index, end)) {
end = text.indexOf(marker, end + marker.length);
}
if (end > index + marker.length) {
flush();
const formatted = document.createElement(tagName);
Expand Down