Alias cycle

This warning category is spelled [alias-cycle] by qmllint.

Alias property is part of an alias cycle

What happened?

A property alias resolves to itself or to another alias resolving to itself.

Usually, a property alias should reference another property either directly, or indirectly by passing through another alias property.

If a property alias directly or indirectly references itself, then it forms an alias cycle. The warning indicates that the current alias property is inside or references an alias cycle, see Example.

Why is this bad?

Instances of components with alias cycles will not be created at runtime: they will be null instead.

Example

import QtQuick

Item {
    id: someId
    property alias myself: someId.myself // not ok: referring to itself

    property alias cycle: someId.cycle2 // not ok: indirectly referring to itself
    property alias cycle2: someId.cycle

    property alias indirect: someId.cycle // not ok: referring to alias indirectly referring to itself
}

To fix this warning, break up the alias cycles:

import QtQuick

Item {
    id: someId
    Item {
        id: anotherId
        property string myself
        property int cycle
    }
    property alias myself: anotherId.myself // ok: referring to a property

    property alias cycle: someId.cycle2 // ok: does not refer to itself anymore
    property alias cycle2: anotherId.cycle // ok: not a cycle anymore

    property alias indirect: someId.cycle // ok: cycle does not form an alias cycle anymore
}