languagetool-org/languagetool · error · RuntimeException

Could not load simple replacement data from: " + path + ". E

Error message

Could not load simple replacement data from: " + path + ". Error in line '" + line + "', replacement cannot be empty

What it means

SimpleReplaceDataLoader.loadWords parses a rule-replacement file where each line must be 'wrongForm=replacement'. This RuntimeException is thrown when the right-hand side of the '=' is empty after trimming, i.e. the data file contains a line like 'word=' with no replacement.

Source

Thrown at languagetool-core/src/main/java/org/languagetool/rules/SimpleReplaceDataLoader.java:53

  /**
   * Load replacement rules from a utf-8 file in the classpath.
   */
  public Map<String, List<String>> loadWords(String path) {
    InputStream stream = JLanguageTool.getDataBroker().getFromRulesDirAsStream(path);
    Map<String, List<String>> map = new HashMap<>();
    try (Scanner scanner = new Scanner(stream, "utf-8")) {
      while (scanner.hasNextLine()) {
        String line = scanner.nextLine();
        if (line.isEmpty() || line.charAt(0) == '#') { // # = comment
          continue;
        }
        String[] parts = line.split("=");
        if (parts.length != 2) {
          throw new RuntimeException("Could not load simple replacement data from: " + path + ". " +
                  "Error in line '" + line + "', expected format 'word=replacement'");
        }
        if (parts[1].trim().isEmpty()) {
          throw new RuntimeException("Could not load simple replacement data from: " + path + ". " +
            "Error in line '" + line + "', replacement cannot be empty");
        }
        String[] wrongForms = parts[0].split("\\|");
        List<String> replacements = Arrays.asList(parts[1].split("\\|"));
        for (String wrongForm : wrongForms) {
          map.put(wrongForm, replacements);
        }
      }
    }
    return Collections.unmodifiableMap(map);
  }

}

View on GitHub (pinned to 2e990059ce)

Solutions

Open the file at 'path' named in the exception and find the offending line printed in the message.
Add a non-empty replacement after the '=' (or remove the line if the entry is not wanted).
Split multiple replacements with '|' if needed, e.g. 'word=fix1|fix2'.

Example fix

// before (data file)
mispeled=
// after (data file)
mispeled=misspelled

Defensive patterns

Strategy: validation

Validate before calling

// validate replacement data lines before loading
for (String line : Files.readAllLines(Paths.get(path))) {
    if (line.isEmpty() || line.startsWith("#")) continue;
    String[] parts = line.split("=", -1);
    if (parts.length != 2 || parts[1].trim().isEmpty())
        throw new IllegalStateException("Bad line in " + path + ": " + line);
}

Try / catch

try { loader.loadWords(path, language); } catch (RuntimeException e) { log.error("Invalid replacement data: " + e.getMessage()); throw e; }

Prevention

Run a linter/CI check on rule data files for empty replacements
Never commit replacement files with lines ending in '='
Test-load all language data files in unit tests

When it happens

Trigger: Calling loadFromPath/loadWords on a replacement data file that contains a line with an empty replacement, e.g. 'mispeled=' (nothing after '=').

Common situations: Hand-edited or incomplete language rule data files in the language resource directories; a contributor deleted the replacement but left the word; file truncated during commit.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

AI-assisted analysis of languagetool-org/languagetool@2e990059ce (2026-09-06). Data as JSON: /api/errors/c32d82bb68de5113. Report an issue: GitHub.