- Qt 6.12
- Qt Qml
- Qt Qml Tooling
- qmllint
- QML Lint Warning and Errors
- Recursion depths errors
- Qt 6.12.0 Reference Documentation

Readonly property ◦ Redundant Optional Chaining

# Recursion depths errors

This warning category is spelled `[recursion-depth-errors]` by qmllint.

## Maximum statement or expression depth exceeded

### What happened?

A QML statement or expression was too deeply nested for the compiler. This usually only happens for generated code where statements or expressions can be very long, as the recursion limit is usually large enough for any sensible QML document.

### Why is this bad?

The QML engine will not be able to run this code.

### Example

     import QtQuick

     Item {
         function f() {
             let x = 1 + 1 + .... + 1 // maximum depth exceeded: add too many ones together
             return x
         }

         Item { Item { .... } } // maximum depth exceeded: too many nested Item's
     }

To fix this warning, auto-generate smaller code pieces. Split deeply nested Components in multiple files or inline components, or split deeply nested expressions into multiple expressions:

     import QtQuick

     Item {
         function f() {
             let x = 1 + 1 + .... + 1 // first half of the split
             x += 1 + 1 + .... + 1 // second half of the split
             return x
         }

         component NestedItem : Item { Item {... }} // first half of the nested Item
         component DeeplyNestedItem: Item { ... NestedItem{} ... } // second half of the nested Items + NestedItem
         DeeplyNestedItem {}
     }

Readonly property ◦ Redundant Optional Chaining