stanfordnlp/CoreNLP · error · Error

Attribute already defined:

Error message

Attribute already defined: 

What it means

A plain java.lang.Error thrown by the grammar's simple attribute assignment production when the same IDENTIFIER attribute is assigned twice with '=' in a parsed attribute list (e.g. tag=NN tag=VB). The parser stores attributes in a Map and refuses to overwrite silently, raising an Error instead. It is not a ParseException.

Solutions

1. Delete or correct the duplicate attribute assignment so each identifier appears once.
2. If both values are intended, combine them (regex alternation or a list construct) under a single key.
3. Deduplicate attributes before generating the pattern string in code.
4. Catch Throwable/Error at the rule-loading boundary since these are Errors, and report the failing rule line.

Example fix

// before
// rule text: { tag=NN tag=VB }
// Error: Attribute already defined: tag
// after
// rule text: { tag:/NN|VB/ }

// Pre-check: no repeated identifier= assignments in the attribute string
static void checkNoDupAssignments(String attrs) {
  java.util.regex.Matcher m = java.util.regex.Pattern.compile("(\\w+)\\s*=").matcher(attrs);
  java.util.Set<String> seen = new java.util.HashSet<>();
  while (m.find()) { if (!seen.add(m.group(1))) throw new IllegalArgumentException("Duplicate attribute: " + m.group(1)); }
}

try {
  parser.parseAttributes(env, attrs);
} catch (Error e) {
  if (e.getMessage() != null && e.getMessage().startsWith("Attribute already defined")) {
    throw new IllegalArgumentException("Duplicate assignment in: " + attrs, e);
  }
  throw e;
}

When it happens

Trigger: Parsing an attribute expression with duplicate identifier assignments, e.g. matching constructs like [tag=NN tag=VB], via the grammar path that parses IDENTIFIER '=' (RelaxedStringToken | NumberToken) attribute pairs.

Common situations: Hand-edited rules where an attribute line was duplicated; generated attribute strings from two configuration sources merged naively; typo making two intended keys identical.

Related errors

• Attribute match already defined
• Attribute already defined
• Field already defined:
• Attribute match already defined:
• Unknown sequence pattern variable

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/aa7d9b3f63ea1895. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/ling/tokensregex/parser/TokenSequenceParser.jj:1108

		"}"
    )
  	{
	  return attributes;
	}
}

Map<String,String> SetAttrValue(Env env, Map<String,String> attributes) : {
	Token attr = null;
	Token value = null;
	String str = null;
}   {
	    attr = <IDENTIFIER>
	    (    "=" (value = RelaxedStringToken() | value = NumberToken() )
	    )
	    { if (value != null) { str = value.image; }
	      if (attr != null && str != null)  {
	        if (attributes.containsKey(attr.image)) {
                throw new Error("Attribute already defined: " + attr.image);
	        }
	        attributes.put(attr.image, str);
	      }
     	  return attributes;
	    }
	}

Token NumberToken() : {
   Token value = null;
} {
  ( value = <NONNEGINT> | value = <INT> | value = <REAL> )
  { return value; }
}

Token IntegerToken() : {
   Token value = null;
} {
  ( value = <NONNEGINT> | value = <INT> )

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