stanfordnlp/CoreNLP · error · UnsupportedOperationException

Expression was not evaluated....

Error message

Expression was not evaluated....

What it means

Expressions.MapValue stores unevaluated Expression objects per attribute. getValue(attr) only supports already-evaluated Values; if the stored expression is not a Value instance, it cannot return it and throws UnsupportedOperationException('Expression was not evaluated....').

Solutions

1. Call evaluate(env, args) on the expression (or the MapValue's expressions) before calling getValue
2. Use the get(String attr)/generic accessor path if it handles evaluation, instead of getValue
3. Check the attribute key: expr==null returns null silently, so a wrong key is not the cause — the key exists but holds an unevaluated Expression
4. If you own the code, evaluate the nested expression and store the resulting Value back into the map

Example fix

// before
Value v = mapValue.getValue("key"); // holds raw Expression
// after
Value v = (Value) expression.evaluate(env).get(); // evaluate first, or use the evaluate() API on the parent expression

Expression e = mapValue.getExpression(attr); // or via underlying map
if (e instanceof Value) {
    Value v = (Value) e;
} else {
    e.evaluate(env); // evaluate before getValue
}

boolean isEvaluated(Expression e) {
    return e instanceof Value;
}

try {
    Value v = mapValue.getValue(attr);
} catch (UnsupportedOperationException e) {
    if (e.getMessage().contains("not evaluated")) {
        // run the evaluation phase, then retry
    } else throw e;
}

When it happens

Trigger: Calling getValue(attr) on a MapValue produced from expressions that were never evaluated — e.g. reading fields of a composite expression result directly instead of calling evaluate() first, or fetching attributes whose expressions are lazy/deferred.

Common situations: Custom code walking TokensRegex expression results and calling getValue() on a nested MapValue before running the evaluation phase, or attributes created by `with`/assignment clauses that weren't evaluated.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

• Cannot find function matching args
• Unknown function
• Unsupported function value
• 2 arguments expected, got
• Annotation field cannot be null

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/36c4e877fe7acb3a. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/ling/tokensregex/types/Expressions.java:1210

      }
      return ok;
    }

    public Set<String> getAttributes() {
      return value.keySet();
    }

    public Expression getExpression(String attr) {
      return value.get(attr);
    }

    public Value getValue(String attr) {
      Expression expr = value.get(attr);
      if (expr == null) return null;
      if (expr instanceof Value) {
        return (Value) expr;
      }
      throw new UnsupportedOperationException("Expression was not evaluated....");
    }

    public <T> T get(String attr) {
      Expression expr = value.get(attr);
      if (expr == null) return null;
      if (expr instanceof Value) {
        return ((Value<T>) expr).get();
      }
      throw new UnsupportedOperationException("Expression was not evaluated....");
    }

    public void set(String attr, Object obj) {
      if (obj instanceof Expression) {
        value.put(attr, (Expression) obj);
      } else {
        value.put(attr, createValue(null, obj));
      }
      evaluated = null;

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