What causes "id is null for rule with name '" in languagetool-org/languagetool?

Add an id attribute to the offending element in the XML file

languagetool-org/languagetool · error · RuntimeException

id is null for rule with name '

Error message

id is null for rule with name '

What it means

PatternRuleHandler parses LanguageTool XML grammar rule files with a SAX handler. Every <rule> must carry an 'id' attribute unless the parser is in relaxedMode; this RuntimeException fires when a rule element ends without an id. Ids are required to reference, enable/disable, and deduplicate rules.

Source

Thrown at languagetool-core/src/main/java/org/languagetool/rules/patterns/PatternRuleHandler.java:235

          if (YES.equals(premiumFileAttribute)) {
            isPremiumRule = true;
          } else if (NO.equals(premiumFileAttribute)) {
            isPremiumRule = false;
          }
        } else {
          isPremiumRule = false;
        }
        if (inRuleGroup) {
          subId++;
          if (id == null) {
            id = ruleGroupId;
          }
          if (name == null) {
            name = ruleGroupDescription;
          }
        }
        if (id == null && !relaxedMode) {
          throw new RuntimeException("id is null for rule with name '" + name + "'");
        }
        id = idPrefix != null ? idPrefix + id : id;
        if (inRuleGroup && ruleGroupDefaultOff && attrs.getValue(DEFAULT) != null) {
          throw new RuntimeException("Rule group " + ruleGroupId + " is off by default, thus a subrule of " + id + " cannot specify 'default=...'. \033[1m Remove 'default=...' from rule group or subrule level in " + ruleGroupId + "!\033[0m");
        }
        if (inRuleGroup && ruleGroupDefaultTempOff && attrs.getValue(DEFAULT) != null) {
          throw new RuntimeException("Rule group " + ruleGroupId + " is off by default, thus a subrule of " + id + " cannot specify 'default=...'. \033[1m Remove 'default=...' from rule group or subrule level in " + ruleGroupId + "!\033[0m");
        }
        if (inRuleGroup && ruleGroupDefaultOff) {
          defaultOff = true;
        } else if (inRuleGroup && ruleGroupDefaultTempOff) {
          defaultTempOff = true;
        } else {
          defaultOff = OFF.equals(attrs.getValue(DEFAULT));
          defaultTempOff = TEMP_OFF.equals(attrs.getValue(DEFAULT));
        }
        correctExamples = new ArrayList<>();
        antipatternExamples = new ArrayList<>();

View on GitHub (pinned to 2e990059ce)

Solutions

Add an id attribute to the offending <rule> element in the XML file
If the rule sits in a <rulegroup>, ensure the group has an id and the rule has its own unique sub-id (or set one)
If parsing third-party/incomplete XML intentionally, enable relaxedMode on the loader so ids are auto-derived

Example fix

// before
<rule>
  <pattern>...</pattern>
</rule>
// after
<rule id="MY_RULE_ID" name="my rule">
  <pattern>...</pattern>
</rule>

Defensive patterns

Strategy: validation

Validate before calling

// Before loading: sanity-check rule XML for ids
Document doc = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(ruleXml);
NodeList rules = doc.getElementsByTagName("rule");
for (int i = 0; i < rules.getLength(); i++) {
  if (rules.item(i).getAttributes().getNamedItem("id") == null)
    throw new IllegalStateException("rule missing id at index " + i);
}

Try / catch

try { loader.parse(ruleXml, "en"); } catch (RuntimeException e) { if (e.getMessage().startsWith("id is null")) { log.error("Fix rule XML: add id attribute"); } throw e; }

Prevention

Always give every <rule> an id and name
Run the rule XML through a schema/DTD check before loading
Keep template files with id placeholders that fail loudly if unfilled

When it happens

Trigger: Parsing a grammar XML where a <rule> element (or its <rulegroup>) lacks an id attribute while relaxedMode is false. Occurs via PatternRuleLoader.parse(...) or JLanguageTool rule loading.

Common situations: Hand-written or edited custom rule XML missing id="..."; XML where rulegroup-level id inheritance was expected but the rule itself needs one; merging rule files that dropped attributes.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of languagetool-org/languagetool@2e990059ce (2026-09-06). Data as JSON: /api/errors/9c9e0b34dfb4c7fd. Report an issue: GitHub.