src/language-js/print/jsx.js/printJsxAttribute
function printJsxAttribute(path, options, print) {
  const n = path.getValue();
  const parts = [];
  parts.push(path.call(print, "name"));

  if (n.value) {
    let res;
    if (isStringLiteral(n.value)) {
      const raw = rawText(n.value);
      // Unescape all quotes so we get an accurate preferred quote
      let final = raw.replace(/&apos;/g, "'").replace(/&quot;/g, '"');
      const quote = getPreferredQuote(
        final,
        options.jsxSingleQuote ? "'" : '"'
      );
      const escape = quote === "'" ? "&apos;" : "&quot;";
      final = final.slice(1, -1).replace(new RegExp(quote, "g"), escape);
      res = concat([quote, final, quote]);
    } else {
      res = path.call(print, "value");
    }
    parts.push("=", res);
  }

  return concat(parts);
}