stanfordnlp/CoreNLP · error · Error

Field already defined:

Error message

Field already defined: 

What it means

FieldValue parses one 'name = expression' entry into an attributes map. If the field name was already put into the attributes map, it throws a java.lang.Error (deliberate, not an Exception) with the message "Field already defined: " plus the name. This is a hard programmatic error signaling duplicate keys in one composite value.

Solutions

1. Remove or rename the duplicate field in the composite value so each name appears once.
2. Search the rule file for repeated field names before the failing '(' ... ')' block.
3. If building attributes programmatically, check attributes.containsKey(name) before inserting.
4. Version-control the rules file so merged duplicates are caught in review.

Example fix

// before
(a = 1, a = 2)
// after
(a = 1, b = 2)

// Detect duplicate field names in a composite block before parsing
Set<String> seen = new HashSet<>();
for (String field : fields) {
    if (!seen.add(fieldName(field))) {
        throw new IllegalArgumentException("Field already defined: " + fieldName(field));
    }
}

try {
    parser.CompositeFieldValue(env, reader);
} catch (Error err) {
    if (err.getMessage() != null && err.getMessage().startsWith("Field already defined")) {
        throw new IllegalArgumentException(err.getMessage());
    }
    throw err;
}

When it happens

Trigger: A composite value or rule body listing the same field twice, e.g. (pattern: ..., pattern: ...) or duplicate attribute names in an extractor rule; FieldValue is only called from CompositeFieldValue, so any duplicated field name inside one '(' ... ')' block triggers it.

Common situations: Copy-pasted rule bodies where an attribute line was duplicated, merging rule files that both define the same field, or generated rules where a template emitted a key twice.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• Unknown sequence pattern variable
• Attribute match already defined
• Attribute already defined
• Unknown field for type , trying to set to
• Incompatible type for type , trying to set to

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/9e696e1eb800424d. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/ling/tokensregex/parser/TokenSequenceParser.java:370

        jj_la1[6] = jj_gen;
        jj_consume_token(-1);
        throw new ParseException();
      }
      FieldValue(env, attributes);
    }
    jj_consume_token(24);
{if ("" != null) return new Expressions.CompositeValue(/*"COMPOSITE", */ attributes, false);}
    throw new Error("Missing return statement in function");
}

  final public Map<String,Expression> FieldValue(Env env, Map<String,Expression> attributes) throws ParseException {String fieldname = null;
        Expression expr = null;
    fieldname = RelaxedString();
    jj_consume_token(34);
    expr = Expression(env);
if (fieldname != null && expr != null)  {
                if (attributes.containsKey(fieldname)) {
                {if (true) throw new Error("Field already defined: " + fieldname);}
                }
                attributes.put(fieldname, expr);
              }
          {if ("" != null) return attributes;}
    throw new Error("Missing return statement in function");
}

  final public Value BasicValue(Env env) throws ParseException {Token tok = null;
        Token head = null;
        Token tail = null;
        SequencePattern.PatternExpr seqRegex = null;
    switch ((jj_ntk==-1)?jj_ntk_f():jj_ntk) {
    case REGEX:{
      tok = jj_consume_token(REGEX);
{if ("" != null) return new Expressions.RegexValue(/*"REGEX",*/ tok.image.substring(1,tok.image.length()-1));}
      break;
      }
    case STR:{

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