stanfordnlp/CoreNLP · error · RuntimeException

Exception thrown while scraping fields from

Error message

Exception thrown while scraping fields from 

What it means

ArgumentParser's option-name scraping helper reflects over a class's fields to collect @Option names. If reflection (or any step in scrapeFields/annotation lookup) throws, the exception is wrapped in this RuntimeException with the class name appended. It signals the option-holder class itself is unusable for argument parsing.

Solutions

1. Fix the underlying exception: this wrapper discards the cause, so reproduce with reflection manually to see the real error.
2. Ensure the option-holder class and all its field types are on the classpath (no NoClassDefFoundError).
3. Check for restrictive SecurityManager/classloader policies blocking reflection on the class.
4. Verify you pass a class that actually declares @Option fields and isn't null/abstract-incompatible.

Example fix

// before
ArgumentParser parser = new ArgumentParser(MyOpts.class, args); // fails if MyOpts fields unloadable
// after
try {
  ArgumentParser parser = new ArgumentParser(MyOpts.class, args);
} catch (RuntimeException e) {
  throw new IllegalStateException("Check MyOpts class deps/policy: " + e.getMessage(), e);
}

// pre-check reflectability
MyOpts o = new MyOpts(); // ensures class + field types load
if (o.getClass().getDeclaredFields().length == 0) throw new IllegalStateException("No fields to scrape");

boolean isReflectable(Class<?> c) { try { c.getDeclaredFields(); return true; } catch (Throwable t) { return false; } }

try { new ArgumentParser(clazz, args); } catch (RuntimeException e) { if (e.getMessage().startsWith("Exception thrown while scraping fields from")) { // reproduce reflection manually to find root cause } throw e; }

When it happens

Trigger: ArgumentParser constructor (public) invoked with an option-holder class c whose fields cannot be reflected over — e.g. a security manager blocks setAccessible, annotation scanning fails, or a NoClassDefFoundError from a missing dependency surfaces during field enumeration.

Common situations: Passing a null or non-option class; running under a restrictive classloader/security policy; a field type referenced in the option class comes from a missing jar so field resolution fails.

Related errors

• Cannot create set of holidays.
• Class " + classname + " could not be cast to the correct…
• Error initializing binder
• Illegal path: cp=
• Multiple declarations of option

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/ac1c152fed8df051. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/util/ArgumentParser.java:739

    }
    return allProperties;
  }

  /**
   * Return the list of {@link ArgumentParser.Option}'s for provided Class
   * @param c The Class to analyze
   * @return A List containing the {@link ArgumentParser.Option} names
   */

  public static List<String> listOptions(Class c) {
    try {
      return Arrays.stream(scrapeFields(c)).map(field -> {
        ArgumentParser.Option[] anns = field.getAnnotationsByType(ArgumentParser.Option.class);
        return (anns.length > 0) ? anns[0].name() : null;
      }
      ).filter(argOpt -> (argOpt != null)).collect(Collectors.toList());
    } catch (Exception e) {
      throw new RuntimeException("Exception thrown while scraping fields from "+c.getName());
    }
  }


  /**
   * Return a string describing the usage of the program this method is called from, given the
   * options declared in the given set of classes.
   * This will print both the static options, and the non-static options.
   *
   * @param optionsClasses The classes defining the options being used by this program.
   * @return A String describing the usage of the class.
   */
  public static String usage(Class[] optionsClasses) {
    String mainClass = threadRootClass();
    StringBuilder b = new StringBuilder();
    b.append("Usage: ").append(mainClass).append(' ');

    List<Pair<Option, Field>> options = new ArrayList<>();

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