stanfordnlp/CoreNLP · error · RuntimeException

Error -- can't setVar to a different string -- old: " +…

Error message

Error -- can't setVar to a different string -- old: " + oldString + " new: " + string

What it means

VariableStrings.setVar throws RuntimeException if the variable already had a binding and the new string differs from the old one. Re-setting a variable to the SAME string is allowed (and increments the set counter), but contradicting an existing binding is treated as a programming error.

Solutions

1. Ensure each variable maps to exactly one value; restructure so conflicting keys are namespaced or the instance is recreated per document.
2. Call unsetVar before rebinding if the overwrite is intentional.
3. Call isVarSet(var) first and skip/branch when already bound to a different value.
4. Catch RuntimeException at the call site to detect the conflict.

Example fix

// before
vs.setVar("$author", doc1Author);
vs.setVar("$author", doc2Author); // throws
// after
if (vs.isVarSet("$author") && !doc2Author.equals(currentAuthor)) {
  vs = new VariableStrings(...); // fresh bindings per document
}
vs.setVar("$author", doc2Author);

// check before rebinding
if (vs.isVarSet(var) && !oldValue.equals(newValue)) {
  throw new IllegalStateException("var " + var + " already bound to " + oldValue);
}

try {
  vs.setVar(var, value);
} catch (RuntimeException e) {
  if (e.getMessage().startsWith("Error -- can't setVar")) {
    vs = new VariableStrings(...); // fresh bindings
  } else throw e;
}

When it happens

Trigger: Calling setVar("$name", "Alice") then later setVar("$name", "Bob") on the same VariableStrings instance; reusing one instance across documents where templates share variable names but different replacements.

Common situations: Batch text templating over a corpus where the same placeholder appears with different intended values; accidental reuse of a populated VariableStrings object for a second pass.

Understand the failure class

Background: Conflicting config options: "cannot be used together" — configuration validation errors across open-source libraries — this error's family across 162 libraries.

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AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/70f0d41b2b4c0b7c. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/util/VariableStrings.java:40

  public VariableStrings(VariableStrings other) {
    varsToStrings = new ArrayMap<>(other.varsToStrings);
    numVarsSet = new IntCounter<>(other.numVarsSet);
  }

  public void reset() {
    numVarsSet.clear();
    varsToStrings.clear();
  }

  public boolean isSet(String o) {
    return numVarsSet.getCount(o) >= 1;
  }

  public void setVar(String var, String string) {
    String oldString = varsToStrings.put(var,string);
    if(oldString != null && ! oldString.equals(string))
      throw new RuntimeException("Error -- can't setVar to a different string -- old: " + oldString + " new: " + string);
    numVarsSet.incrementCount(var);
  }

  public void unsetVar(String var) {
    if(numVarsSet.getCount(var) > 0)
      numVarsSet.decrementCount(var);
    if(numVarsSet.getCount(var)==0)
      varsToStrings.put(var,null);
  }

  public String getString(String var) {
    return varsToStrings.get(var);
  }

  @Override
  public String toString() {
    StringBuilder s = new StringBuilder();
    s.append("{");

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