pentaho/pentaho-kettle · error · Error

Can't reverse a sorted list.

Error message

Can't reverse a sorted list.

What it means

Mutation guard on the SortedList prototype in the Pentaho client UI: reverse() was called on a list that maintains sort order invariantly. All order-destroying operations (copyWithin, fill, reverse, unshift, indexed insert) throw to preserve the sorted invariant.

Solutions

1. Iterate the list backwards instead of mutating it
2. Create a new SortedList with an inverted comparer for descending order
3. Copy to a plain array/Array and reverse that copy

Example fix

// before
sortedList.reverse(); // throws
// after
for (var i = sortedList.count - 1; i >= 0; i--) process(sortedList.at(i));

if (list.isSorted) {
  throw new TypeError('reverse is unsupported on SortedList');
}

try {
  list.reverse();
} catch (e) {
  if (String(e.message).indexOf('reverse a sorted list') >= 0) {
    for (var i = list.count - 1; i >= 0; i--) process(list.at(i));
  } else throw e;
}

When it happens

Trigger: Any call to sortedList.reverse(), directly or via array-generic code that reverses in place.

Common situations: Trying to display a sorted list in descending order; porting List code to SortedList; array-generic helpers iterating/reversing collections.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Can't copy within a sorted list.
• Can't do a indexed insert in a sorted list.
• Can't do a indexed replace in a sorted list.
• Can't fill a sorted list.
• Append file in repository is not possible

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/83f45d83e9ab66df. Report an issue: GitHub.

Appendix: source

Thrown at plugins/core-ui/src/main/resources/app/pentaho/lang/SortedList.js:175

          return i;
        }
      }

      // two's complement operation being used to
      // return (x+1)*-1 in a hackish way
      return ~left;
    },

    copyWithin: function() {
      throw new Error("Can't copy within a sorted list.");
    },

    fill: function() {
      throw new Error("Can't fill a sorted list.");
    },

    reverse: function() {
      throw new Error("Can't reverse a sorted list.");
    },

    unshift: function() {
      throw new Error("Can't do a indexed insert in a sorted list.");
    },

    insert: function() {
      throw new Error("Can't do a indexed insert in a sorted list.");
    },

    replace: function() {
      throw new Error("Can't do a indexed replace in a sorted list.");
    },

    splice: function() {
      if(arguments.length > 2) {
        throw new Error("Can't do a indexed insert in a sorted list.");
      }

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