stanfordnlp/CoreNLP · error · java.lang.IllegalArgumentException

StringRegex binding error: Invalid variable name

Error message

StringRegex binding error: Invalid variable name 

What it means

Env.bindStringRegex enforces that string-regex substitution variable names match $[A-Za-z0-9_]+. Binding a name with other characters (spaces, hyphens, missing $, unicode) throws this IllegalArgumentException before any substitution happens.

Solutions

1. Prefix the variable name with $ and use only letters, digits, and underscores: $VAR1
2. Sanitize generated names before calling bindStringRegex

Example fix

// before
env.bindStringRegex("myvar", "foo|bar");
// after
env.bindStringRegex("$myvar", "foo|bar");

private static final Pattern NAME = Pattern.compile("\\$[A-Za-z0-9_]+");
if (var == null || !NAME.matcher(var).matches()) throw new IllegalArgumentException("StringRegex var must match $[A-Za-z0-9_]+: " + var);
env.bindStringRegex(var, regex);

boolean isValidStringRegexVar(String v) { return v != null && v.matches("\\$[A-Za-z0-9_]+"); }

try { env.bindStringRegex(var, regex); } catch (IllegalArgumentException e) { log.warn("Skipping invalid string-regex var: {}", var); }

When it happens

Trigger: Calling env.bindStringRegex(var, regex) with a name like 'myvar' (no leading $), '$my-var', or an empty string.

Common situations: Programmatic binding of substitution variables with auto-generated names, or misunderstanding that the $ prefix is mandatory.

Understand the failure class

Background: "invalid id" errors: invalid identifier format — why libraries reject IDs before lookup, and how to fix them — this error's family across 37 libraries.

Related errors

• Unable get expression for variable
• 2 arguments expected, got
• Annotation field cannot be null
• : Entry has multiple types for : . Taking type to be
• Attribute already defined:

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/8bb8c1b384635e49. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/ling/tokensregex/Env.java:289

  public void setDefaultStringPatternFlags(int defaultStringPatternFlags) {
    this.defaultStringPatternFlags = defaultStringPatternFlags;
  }

  public int getDefaultStringMatchFlags() {
    return defaultStringMatchFlags;
  }

  public void setDefaultStringMatchFlags(int defaultStringMatchFlags) {
    this.defaultStringMatchFlags = defaultStringMatchFlags;
  }

  private static final Pattern STRING_REGEX_VAR_NAME_PATTERN = Pattern.compile("\\$[A-Za-z0-9_]+");
  public void bindStringRegex(String var, String regex)
  {
    // Enforce requirements on variable names ($alphanumeric_)
    if (!STRING_REGEX_VAR_NAME_PATTERN.matcher(var).matches()) {
      throw new IllegalArgumentException("StringRegex binding error: Invalid variable name " + var);
    }
    Pattern varPattern = Pattern.compile(Pattern.quote(var));
    String replace = Matcher.quoteReplacement(regex);
    stringRegexVariables.put(var, new Pair<>(varPattern, replace));
  }

  public String expandStringRegex(String regex) {
    // Replace all variables in regex
    String expanded = regex;
    for (Map.Entry<String, Pair<Pattern, String>> stringPairEntry : stringRegexVariables.entrySet()) {
      Pair<Pattern,String> p = stringPairEntry.getValue();
      expanded = p.first().matcher(expanded).replaceAll(p.second());
    }
    return expanded;
  }

  public Pattern getStringPattern(String regex) {
    String expanded = expandStringRegex(regex);

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