stanfordnlp/CoreNLP · error · IllegalArgumentException

Unsupported dependency type:

Error message

Unsupported dependency type: 

What it means

Sentence's internal call to impl.dependencies(mode) hits the default branch of a switch over GrammaticalStructure.DependencyMode when the mode value is unrecognized, throwing IllegalArgumentException with 'Unsupported dependency type: ' + mode. In practice the three enum cases (BASIC, ENHANCED, ENHANCED_PLUS_PLUS) cover all values, so this is a defensive invariant guard reached only if a new enum constant is added without updating this switch.

Solutions

1. Use only DependencyMode.BASIC, ENHANCED, or ENHANCED_PLUS_PLUS
2. Upgrade/align CoreNLP jars so the enum and Sentence come from the same version
3. Check for library bug if it occurs with stock API and report to CoreNLP maintainers

Example fix

// before
SemanticGraph g = sentence.dependencies(GrammaticalStructure.DependencyMode.ENHANCED_PLUS_PLUS);
// after
if (mode != BASIC && mode != ENHANCED && mode != ENHANCED_PLUS_PLUS) {
  mode = GrammaticalStructure.DependencyMode.BASIC;
}
SemanticGraph g = sentence.dependencies(mode);

// restrict mode to known values
if (mode != GrammaticalStructure.DependencyMode.BASIC
 && mode != GrammaticalStructure.DependencyMode.ENHANCED
 && mode != GrammaticalStructure.DependencyMode.ENHANCED_PLUS_PLUS) {
  mode = GrammaticalStructure.DependencyMode.BASIC;
}

boolean isValidDependencyMode(GrammaticalStructure.DependencyMode m) {
  return m == BASIC || m == ENHANCED || m == ENHANCED_PLUS_PLUS;
}

try {
  SemanticGraph g = sentence.dependencies(mode);
} catch (IllegalArgumentException e) {
  SemanticGraph g = sentence.dependencies(GrammaticalStructure.DependencyMode.BASIC);
}

When it happens

Trigger: Calling Sentence.dependencies(), governors(), governor(), incomingDependencyLabel(s), or dependencyGraph() with a dependency mode that the underlying impl does not map; mainly occurs after custom extensions or a version mismatch introducing a new DependencyMode constant.

Common situations: Upgrading CoreNLP where a new DependencyMode was added but Sentence's switch not updated; reflection or serialization restoring a stale/unexpected mode value.

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

• Unknown sentiment class:
• Shouldn't happen:
• Error reading saved links
• RuntimeIOException wrapping IOException
• Error creating data exporter

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/3d751b7acb5161e2. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/simple/Sentence.java:658

  }

  /** @see Sentence#parse(java.util.Properties) */
  public Tree parse() {
    return parse(this.defaultProps);
  }


  /** An internal helper to get the dependency tree of the given type. */
  private CoreNLPProtos.DependencyGraph dependencies(SemanticGraphFactory.Mode mode) {
    switch (mode) {
      case BASIC:
        return impl.getBasicDependencies();
      case ENHANCED:
        return impl.getEnhancedDependencies();
      case ENHANCED_PLUS_PLUS:
        return impl.getEnhancedPlusPlusDependencies();
      default:
        throw new IllegalArgumentException("Unsupported dependency type: " + mode);
    }
  }

  /**
   * Returns the governor of the given index, according to the passed dependency type.
   * The root has index -1.
   *
   * @param props The properties to use in the parser annotator.
   * @param index The index of the dependent word ZERO INDEXED. That is, the first word of the sentence
   *              is index 0, not 1 as it would be in the {@link edu.stanford.nlp.semgraph.SemanticGraph} framework.
   * @param mode  The type of dependency to use (e.g., basic, collapsed, collapsed cc processed).
   * @return The index of the governor, if one exists. A value of -1 indicates the root node.
   */
  public Optional<Integer> governor(Properties props, int index, SemanticGraphFactory.Mode mode) {
    document.runDepparse(props);
    for (CoreNLPProtos.DependencyGraph.Edge edge : dependencies(mode).getEdgeList()) {
      if (edge.getTarget() - 1 == index) {
        return Optional.of(edge.getSource() - 1);

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