pentaho/pentaho-kettle · error · pentaho.lang.OperationInvalidError

Merge operation ' ' is not defined.

Error message

Merge operation '${op}' is not defined.

What it means

`__mergeOne` in pentaho/util/spec.js performs a named merge operation (replace, merge, etc.) on a target property. If the operation name (from the value's `__mergeOp` or the spec) is not a registered handler in `_mergeHandlers`, it throws OperationInvalidError. This guards against typos or unsupported custom ops.

Solutions

1. Correct the operation name to a registered handler (e.g. 'replace' or 'merge')
2. Register a custom handler in _mergeHandlers before calling merge with that op
3. Log available op names to verify the expected value

Example fix

// before
var spec = { width: { value: 100, __mergeOp: "overwrite" } };
// after
var spec = { width: { value: 100, __mergeOp: "replace" } };

var KNOWN_OPS = Object.keys(require("pentaho/util/spec")._mergeHandlers || {});
if (op && !KNOWN_OPS.includes(op)) throw new Error("Unknown merge op: " + op);

function isKnownMergeOp(op) { return typeof op === "string" && ["replace","merge"].includes(op); }

try { merge(target, source); } catch (e) { if (e instanceof OperationInvalidError) { console.error("Bad __mergeOp in", source); } throw e; }

When it happens

Trigger: Merging a spec/source value whose merge operation name is misspelled (e.g. `__mergeOp: "mrege"`) or names an op that was never registered in `_mergeHandlers`.

Common situations: Typo in a `__mergeOp` annotation; custom merge handler removed or renamed in a version upgrade; passing an op string built dynamically at runtime.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• GPLoad.Exception.MatchColumnsNeeded
• No data output data type was specified for new field
• rule.select.module
• Script.Log.CouldNotAttachAdditionalScripts
• ScriptValuesMetaMod.Exception.FieldToReplaceNotFound

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/01b0293e202366d9. Report an issue: GitHub.

Appendix: source

Thrown at plugins/core-ui/src/main/resources/app/pentaho/util/spec.js:102

      //   {$op: "merge", value: {}}
      if((op = sourceValue.$op)) {
        // Always deref source value, whether or not `op` is merge.
        sourceValue = sourceValue.value;

        // Merge operation only applies between two plain objects and
        // add operation only applies between two arrays.
        // Otherwise behaves like _replace_.
        if(op === "merge" && !__isPlainJSObject(sourceValue) || op === "add" && !Array.isArray(sourceValue)) {
          op = "replace";
        }
      } else {
        op = "merge";
      }
    }

    var handler = O.getOwn(_mergeHandlers, op || "replace");
    if(!handler)
      throw new OperationInvalidError("Merge operation '" + op + "' is not defined.");

    handler(target, name, sourceValue);
  }

  /**
   * Performs the merge operation when the target value is also a plain object,
   * or replaces it, if not.
   *
   * @param {object} target - The target object.
   * @param {string} name - The source property name.
   * @param {object} sourceValue - The source property value.
   *
   * @private
   */
  function __mergeOperMerge(target, name, sourceValue) {
    // Is `targetValue` also a plain object?
    var targetValue = target[name];
    if(__isPlainJSObject(targetValue))

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