renderFragments method

String renderFragments(String source, { required List<String> fragments, required Map<String, dynamic> context, })

Render multiple named fragments from a template string, concatenated in order.

Designed for HTMX OOB (out-of-band) swap responses. Each fragment is processed independently with the same context. Fails fast if any fragment is missing — no partial output is returned.

Implementation

String renderFragments(String source, {required List<String> fragments, required Map<String, dynamic> context}) {
  if (fragments.isEmpty) return '';

  var doc = _parse(source);
  doc = _resolveInheritance(doc);
  final attrPrefix = '$prefix$separator';
  final escapedPrefix = escapeAttrSelector(attrPrefix);

  // Fail-fast: find and clone all fragment elements before processing any
  final clones = <Element>[];
  for (final name in fragments) {
    final el = doc.querySelector('[${escapedPrefix}fragment="$name"]');
    if (el == null) throw FragmentNotFoundException(name);
    clones.add(el.clone(true));
  }

  // Process each clone independently
  final processor = _createProcessor()..collectFragments(doc);
  final buffer = StringBuffer();
  for (final clone in clones) {
    processor.process(clone, context);
    clone.attributes.remove('${attrPrefix}fragment');
    buffer.write(_elementHtml(clone, attrPrefix));
  }

  return buffer.toString();
}