dedupeSharedSwiftDecls function

String dedupeSharedSwiftDecls(
  1. String content,
  2. Set<String> alreadyDefined
)

Removes top-level shared declarations already defined by an earlier bridge file compiled into the same Swift module, tracking what has been seen cumulatively in alreadyDefined (caller keeps one set per module).

Unlike stripSharedSwiftPreamble — which removes a fixed window starting at public protocol NitroEncodable — this handles bridges that carry any SUBSET of the shared declarations. A record-only spec, for example, emits NitroRecordWriter/NitroRecordReader but no NitroEncodable; two such bridges in one SPM target would otherwise collide with "'NitroRecordWriter' is ambiguous for type lookup".

The first file processed passes through unchanged (nothing is in alreadyDefined yet) and registers its declarations; later files keep only declarations not yet seen.

Implementation

String dedupeSharedSwiftDecls(String content, Set<String> alreadyDefined) {
  final lines = content.split('\n');
  final result = <String>[];
  var i = 0;
  while (i < lines.length) {
    final line = lines[i];
    final match = _sharedSwiftDeclRe.firstMatch(line);
    if (match == null) {
      result.add(line);
      i++;
      continue;
    }
    final declName = match.group(1)!;
    if (alreadyDefined.add(declName)) {
      // First definition in this module — keep it (block body is copied by
      // the normal flow since its lines don't match the declaration regex).
      result.add(line);
      i++;
      continue;
    }
    // Duplicate — skip the whole brace-balanced block.
    var depth = 0;
    var seenOpen = false;
    while (i < lines.length) {
      for (final ch in lines[i].codeUnits) {
        if (ch == 0x7B) {
          depth++;
          seenOpen = true;
        } else if (ch == 0x7D) {
          depth--;
        }
      }
      i++;
      if (seenOpen && depth <= 0) break;
    }
    // Swallow one trailing blank line so the output stays tidy.
    if (i < lines.length && lines[i].trim().isEmpty) i++;
  }
  return result.join('\n');
}