What causes "suppressMisspelledMatch must be a valid regex" in languagetool-org/languagetool?

Fix the suppressMisspelledMatch option value to be valid Java regex syntax (e.g. '\\bmisspelled\\b').

languagetool-org/languagetool · error · IllegalArgumentException

suppressMisspelledMatch must be a valid regex

Error message

suppressMisspelledMatch must be a valid regex

What it means

RemoteRule's constructor compiles the optional service option 'suppressMisspelledMatch' as a java.util.regex.Pattern. If the option value is present but not syntactically valid regex, PatternSyntaxException is rethrown as IllegalArgumentException with this message.

Source

Thrown at languagetool-core/src/main/java/org/languagetool/rules/RemoteRule.java:91

    this.lt = this.ruleLanguage.createDefaultJLanguageTool();
    this.inputLogging = inputLogging;
    if (ruleId == null) { // allow both providing rule ID in constructor or overriding getId
      ruleId = getId();
    }
    filterMatches = Boolean.parseBoolean(serviceConfiguration.getOptions().getOrDefault("filterMatches", "false"));
    whitespaceNormalisation = Boolean.parseBoolean(serviceConfiguration.getOptions().getOrDefault("whitespaceNormalisation", "true"));
    fixOffsets = Boolean.parseBoolean(serviceConfiguration.getOptions().getOrDefault("fixOffsets", "true"));
    premium = Boolean.parseBoolean(serviceConfiguration.getOptions().getOrDefault("premium", "false"));
    boolean includedInHiddenMatches = Boolean.parseBoolean(serviceConfiguration.getOptions().getOrDefault("includedInHiddenMatches", "true"));
    setIncludedInHiddenMatches(includedInHiddenMatches);
    try {
      if (serviceConfiguration.getOptions().containsKey("suppressMisspelledMatch")) {
        suppressMisspelledMatch = Pattern.compile(serviceConfiguration.getOptions().get("suppressMisspelledMatch"));
      } else {
        suppressMisspelledMatch = null;
      }
    } catch(PatternSyntaxException e) {
      throw new IllegalArgumentException("suppressMisspelledMatch must be a valid regex", e);
    }
    try {
      if (serviceConfiguration.getOptions().containsKey("suppressMisspelledSuggestions")) {
        suppressMisspelledSuggestions = Pattern.compile(serviceConfiguration.getOptions().get("suppressMisspelledSuggestions"));
      } else {
        suppressMisspelledSuggestions = null;
      }
    } catch(PatternSyntaxException e) {
      throw new IllegalArgumentException("suppressMisspelledSuggestions must be a valid regex", e);
    }
  }

  public RemoteRule(Language language, ResourceBundle messages, RemoteRuleConfig config, boolean inputLogging) {
    this(language, messages, config, inputLogging, null);
  }

  public static void shutdown() {
    shutdownRoutines.forEach(Runnable::run);

View on GitHub (pinned to 2e990059ce)

Solutions

Fix the suppressMisspelledMatch option value to be valid Java regex syntax (e.g. '\\bmisspelled\\b').
Test the pattern with Pattern.compile() in a snippet or a regex validator set to Java flavor.
Remove the option entirely if suppression is not needed (it is optional).
Check escaping in the config file format (properties/JSON may require doubling backslashes).

Example fix

// before (config)
suppressMisspelledMatch=*.ogg
// after
suppressMisspelledMatch=.*\\.ogg

Defensive patterns

Strategy: try-catch

Validate before calling

String opt = serviceConfig.getOptions().get("suppressMisspelledMatch");
if (opt != null) {
  try { java.util.regex.Pattern.compile(opt); }
  catch (java.util.regex.PatternSyntaxException e) {
    throw new IllegalArgumentException("suppressMisspelledMatch is not valid regex: " + e.getMessage());
  }
}

Try / catch

try {
  rule = new RemoteRule(language, messages, config, inputLogging);
} catch (IllegalArgumentException e) {
  LOG.error("RemoteRule config rejected: {}", e.getMessage());
  throw e; // config must be fixed before retry
}

Prevention

Validate regex options at config-load time, not rule-construction time
Remember Java regex escaping in properties/JSON files
Test remote-rule configs with Pattern.compile in a smoke test

When it happens

Trigger: Configuring a remote rule's RemoteRuleConfig options with suppressMisspelledMatch set to an invalid regex string (unbalanced parens, dangling quantifier, bad escape).

Common situations: Typing a glob-style pattern ('*.ogg') where a regex is required, escaping confusion in config/JSON files (e.g. '\\b' vs '\b'), or copy-pasting patterns with shell-mangled backslashes.

Related errors

AI-assisted analysis of languagetool-org/languagetool@2e990059ce (2026-09-06). Data as JSON: /api/errors/cdff8c4c856ac6da. Report an issue: GitHub.