pentaho/pentaho-kettle · error · ArgumentInvalidError

Module with id ' ' specifies an alias which is already…

Error message

Module with id '{id}' specifies an alias which is already taken: '{alias}'.

What it means

pentaho.lang.ArgumentInvalidError thrown by prepareModule when a module declares an `alias` that is already in use — either by an already-registered module (this.__get(alias) hits) or by another entry in the same batch. Aliases must be unique across the module registry.

Solutions

Change the alias of the new module to a unique string.
Remove the alias from one of the conflicting modules.
Search the config/plugins for the alias string to find all users of it.

Example fix

// before
{"x": {"alias": "chart"}, "y": {"alias": "chart"}}
// after
{"x": {"alias": "chart"}, "y": {"alias": "chart2"}}

Defensive patterns

Strategy: validation

Validate before calling

var aliases = {};
Object.keys(map).forEach(function(k) {
  var a = map[k] && map[k].alias;
  if(a && (aliases[a] || k === a || map[a])) throw new Error("alias taken: " + a);
  if(a) aliases[a] = k;
});

Type guard

null

Try / catch

try { metaService.__configure(map); } catch(e) { if(/already taken/.test(e.message)) { console.warn(e.message); } else { throw e; } }

Prevention

Namespace aliases per plugin to avoid collisions
Grep config for an alias before adopting it

When it happens

Trigger: Defining two modules whose `alias` properties are equal, or defining a module whose alias collides with an existing module's id/alias registered earlier in the MetaService.

Common situations: Two plugins/annotations choosing the same short alias; renaming a module but leaving the old alias on a second module; shared config fragments each defining the same alias.

Understand the failure class

Background: Conflicting config options: "cannot be used together" — configuration validation errors across open-source libraries — this error's family across 162 libraries.

Related errors

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/2c324fbb8dd53077. Report an issue: GitHub.

Appendix: source

Thrown at plugins/core-ui/src/main/resources/app/pentaho/_core/module/MetaService.js:122

            if(O.hasOwn(preparedModuleSpecMap, id)) {
              throw new ArgumentInvalidError(
                "moduleSpecMap",
                "A module with the id or alias '" + id + "' is already being defined.");
            }

            moduleSpec = Object.create(moduleSpec);
            moduleSpec.id = id;
            moduleSpec.index = nextModuleIndex++;

            preparedModuleIdList.push(id);

            // Index by id and by alias, if any.
            preparedModuleSpecMap[id] = moduleSpec;

            var alias = textUtil.nonEmptyString(moduleSpec.alias);
            if(alias !== null && alias !== id) {
              if(this.__get(alias) !== null || O.hasOwn(preparedModuleSpecMap, alias)) {
                throw new ArgumentInvalidError(
                  "moduleSpecMap",
                  "Module with id '" + id + "' specifies an alias which is already taken: '" + alias + "'.");
              }

              preparedModuleSpecMap[alias] = moduleSpec;
            }
          }
        }

        function moduleResolver(idOrAlias, expectedKind) {

          var module = me.__get(idOrAlias);
          if(module === null) {
            var preparedModuleSpec = O.getOwn(preparedModuleSpecMap, idOrAlias, null);
            if(preparedModuleSpec === null) {
              throw new ArgumentInvalidError(
                "moduleSpecMap",
                "A module with id '" + idOrAlias + "' is not defined.");

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