mozilla/pdf.js · error · Error

Invalid token in index.

Error message

Invalid token in index.

What it means

Thrown by SimpleExprParser.parseIndex() in the XFA FormCalc parser when an array index uses the wildcard form '[*]' but the '*' is not immediately followed by a closing ']'. FormCalc uses '[*]' to denote AstEveryOccurence (all occurrences of a SOM node); any token other than ']' after the '*' is rejected. The error message comes from Errors.index.

Source

Thrown at src/core/xfa/formcalc_parser.js:493

      const [tok, param] = parser.parse();
      if (param) {
        params.push(param);
      }
      if (tok.id === TOKEN.rightParen) {
        return params;
      } else if (tok.id !== TOKEN.comma) {
        throw new Error(Errors.params);
      }
      parser.reset();
    }
  }

  static parseIndex(lexer) {
    let tok = lexer.next();
    if (tok.id === TOKEN.times) {
      tok = lexer.next();
      if (tok.id !== TOKEN.rightBracket) {
        throw new Error(Errors.index);
      }
      return new AstEveryOccurence();
    }
    const [token, expr] = new SimpleExprParser(lexer).parse(tok);
    if (token.id !== TOKEN.rightBracket) {
      throw new Error(Errors.index);
    }
    return expr;
  }

  pushOperator(op) {
    this.flushWithOperator(op);
    this.operators.push(op);
    this.last = OPERATOR;
  }

  pushOperand(op) {
    this.operands.push(op);

View on GitHub (pinned to 5903d58d58)

Solutions

1. Inspect the offending FormCalc script in the XFA packet (the SOM reference with '[*') and ensure every '[*]' is written exactly as bracket-star-bracket.
2. Regenerate or repair the XFA form source (XDP/PDF) with a conformant FormCalc authoring tool rather than hand-editing the script bytes.
3. If you do not control the PDF, catch the parser error at the XFA-binding layer and skip the malformed script so the rest of the document still renders.
4. Verify the FormCalc token stream with a standalone FormCalc lexer to confirm the '*' is immediately followed by ']' in the source text.

Example fix

// before (FormCalc source inside XFA)
var x = Subform[* +1];
// after
var x = Subform[*];

// Validate a FormCalc wildcard index before binding the XFA script.
// Rejects '[*]' patterns not written as exactly [*].
function hasMalformedWildcard(script) {
  // matches '[*' not immediately followed by ']'
  return /\[\*(?!\])/.test(script);
}
if (hasMalformedWildcard(formCalcSrc)) {
  // skip binding this script; log the offset
}

// Wrap XFA script evaluation; FormCalc parse errors are plain Error.
try {
  bindFormCalcScript(xfaNode, src);
} catch (e) {
  if (e instanceof Error && /Invalid token in index\./.test(e.message)) {
    console.warn("Skipping malformed FormCalc index script", e.message);
    return;
  }
  throw e;
}

When it happens

Trigger: A FormCalc index expression like 'foo[* +' or 'foo[* x]' — i.e., the lexer emitted TOKEN.times for the '*' but the next token is not TOKEN.rightBracket. Reached when PDF.js evaluates an XFA form's script (calc/event/initialize) containing such a wildcard reference.

Common situations: Loading an XFA-enabled PDF whose embedded FormCalc script has a typo in a wildcard subscript; a hand-edited or generator-emitted XFA packet with malformed '*'; a corrupted/truncated form script where bytes were dropped inside '[*]'.

Understand the failure class

• Authentication and authorization failures — expired tokens, bad credentials, and missing scopes.

Related errors

• Invalid token in Form code
• Invalid token in do ... end declaration.
• Invalid token in var declaration.
• Invalid token in func declaration.
• Invalid token if ... endif declaration.

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/de5b9418acc27029. Report an issue: GitHub.