xai-org/x-algorithm · error · ParseFailure

Duplicated argument name %s

Error message

Duplicated argument name %s

What it means

Enforced by Parser.buildParams: every parameter name in a params/DF signature must be unique. While iterating ARG nodes it accumulates names in argNames and throws ParseFailure if a name repeats, since duplicate named parameters would make argument binding ambiguous.

Source

Thrown at botmaker/src/java/com/twitter/botmaker/compiler/Parser.java:188

    boolean hasOpt = false;
    for (int i = 0; i < params.getChildCount(); i++) {
      Tree arg = params.getChild(i);
      if (arg.getType() == BotMakerLexer.ARG) {
        String name = arg.getChild(1).getText();
        if (arg.getChildCount() == 2 && hasOpt) {
          throw new ParseFailure(
              String.format(
                  "Non-optional parameter %s must be declared before optional parameters.",
                  name));
        } else if (arg.getChildCount() == 2) {
          ret.add(Tuple.of(arg.getChild(0), name, Optional.absent()));
        } else {
          hasOpt = true;
          ret.add(Tuple.of(arg.getChild(0), name, Optional.of(arg.getChild(2))));
        }

        if (argNames.contains(name)) {
          throw new ParseFailure("Duplicated argument name " + name);
        }
        argNames.add(name);
      }
    }
    return ret.build();
  }

  public static Tree parseType(String expr) throws ParseFailure {

    CharStream input = new ANTLRStringStream(expr);
    BotMakerLexer lexer = new BotMakerLexer(input);
    CommonTokenStream tokenStream = new CommonTokenStream(lexer);
    BotMakerParser parser = new BotMakerParser(tokenStream);
    Tree root;
    try {
      root = (Tree) parser.type().getTree();
    } catch (Exception e) {
      if (e.getCause() instanceof RecognitionException) {

View on GitHub (pinned to 24c60942c5)

Solutions

1. Rename or remove the duplicated argument identified in the message
2. Diff the signature against its previous version to find the accidental copy/paste or merge artifact
3. Add a config lint that rejects duplicate parameter names before submission

Example fix

// before
#params(userId, threshold=0.5, threshold=0.9)

// after
#params(userId, threshold=0.5, thresholdHigh=0.9)

// Check for duplicate names before calling the parser
boolean noDuplicates(List<String> names) {
  return names.stream().distinct().count() == names.size();
}

try { Parser.parseParams(sig); } catch (ParseFailure pf) { /* message contains the duplicated name */ }

When it happens

Trigger: A signature like #params(a, a=1) or #param(x, x) — the same argument name appearing twice in one parameter list.

Common situations: Copy/paste of a parameter line when extending a signature, or merge conflicts in config files producing duplicated lines.

Related errors

• Non-optional parameter %s must be declared before optional p
• Failed to parse DF signature '%s'%s
• unknown parse failure
• Failed to parse Type signature '%s'%s
• batch size must be a positive integer

AI-assisted analysis of xai-org/x-algorithm@24c60942c5 (2026-08-28). Data as JSON: /api/errors/039e8813e123a2e3. Report an issue: GitHub.