stanfordnlp/CoreNLP · error · IllegalArgumentException

Unknown MissingLabels mode " + missing

Error message

Unknown MissingLabels mode " + missing

What it means

After a label lookup fails, setLabels switches on the configured MissingLabels policy (FAIL, DEFAULT, KEEP_ORIGINAL); any other enum value reaches the default branch and throws IllegalArgumentException naming the unknown mode. This is an internal-guard against an invalid MissingLabels enum value.

Solutions

  1. Use only the defined MissingLabels enum constants: FAIL, DEFAULT, KEEP_ORIGINAL
  2. Fix code passing null or an invalid value into setLabels
  3. Align CoreNLP jar versions across the classpath to avoid stale enum constants
  4. Validate/parse the missing-labels option through the enum's valueOf with error handling

Example fix

// before
setLabels(tree, labelMap, missing, defaultLabel, unknowns); // missing == null
// after
if (missing == null) missing = MissingLabels.FAIL;
setLabels(tree, labelMap, missing, defaultLabel, unknowns);
Defensive patterns

Strategy: type-guard

Validate before calling

if (missing == null) missing = MissingLabels.FAIL;
// ensure it is one of the enum constants
MissingLabels.valueOf(missing.name());

Type guard

static boolean isValidMissing(MissingLabels m) {
  return m == MissingLabels.FAIL || m == MissingLabels.DEFAULT || m == MissingLabels.KEEP_ORIGINAL;
}

Try / catch

try {
  setLabels(tree, labelMap, missing, defaultLabel, unknowns);
} catch (IllegalArgumentException e) {
  if (e.getMessage().startsWith("Unknown MissingLabels")) missing = MissingLabels.FAIL;
  else throw e;
}

Prevention

When it happens

Trigger: Invoking setLabels(tree, labelMap, missing, defaultLabel, unknowns) programmatically with a MissingLabels value outside the defined enum constants (e.g. null or a stale enum from an incompatible jar version).

Common situations: Reflection/config-driven construction of a MissingLabels value that no longer exists after a Stanford CoreNLP version upgrade; passing null where an enum is expected; mixing jars of different CoreNLP versions on the classpath.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/3c0d0dd9e42c370f. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/parser/tools/ParseAndSetLabels.java:83

      return;
    }
    String text = SentenceUtils.listToString(tree.yield());
    String label = labelMap.get(text);
    if (label != null) {
      tree.label().setValue(label);
    } else {
      switch (missing) {
      case FAIL:
        throw new RuntimeException("No label for '" + text + "'");
      case DEFAULT:
        tree.label().setValue(defaultLabel);
        unknowns.add(text);
        break;
      case KEEP_ORIGINAL:
        // do nothing
        break;
      default:
        throw new IllegalArgumentException("Unknown MissingLabels mode " + missing);
      }
    }
    for (Tree child : tree.children()) {
      setLabels(child, labelMap, missing, defaultLabel, unknowns);
    }
  }

  public static Set<String> setLabels(List<Tree> trees, Map<String, String> labelMap,
                                      MissingLabels missing, String defaultLabel) {
    logger.info("Setting labels");

    Set<String> unknowns = new HashSet<>();

    for (Tree tree : trees) {
      setLabels(tree, labelMap, missing, defaultLabel, unknowns);
    }

    return unknowns;

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