IssueTracker

Jetpack Compose version: 1.3.0-alpha04 Jetpack Compose component used: UI

Consider the following DelegateableNode instances.

internal val ModifierLocalFoo = modifierLocalOf<Foo?> { null }

class DoFooNode: Modifier.Node, ModifierLocalModifierNode {

    val foo = Foo()

    override val providedValues: ModifierLocalMap = modifierLocalMapOf(
        ModifierLocalDragDropParent to foo
    )
}

class UseFooNode: DelegatingNode() {
    val delegated = delegate(DoFooNode())
}

class UseFooNodeInASpecificWay: DelegatingNode() {
    val delegatedFoo = delegate(UseFooNode())
}

If I try to read foo using ModifierLocalFoo.current in a DoFooNode that:

• A UseFooNode delegates to
• and a UseFooNodeInASpecificWay also delegates to that instance of UseFooNode

a circular dependency is introduced because ModifierLocalModifierNode depends on the implementation of visitAncestors which has this line:

var node: Modifier.Node? = if (includeSelf) node else node.parent

In the case of DoFooNode with 2 layers of delegation:

• node will point to UseFooNode.
• node.parent will point to UseFooNodeInASpecificWay.
• When UseFooNodeInASpecificWay.providedValues is called it will delegate back to its instance of DoFooNode which is the calling DoFooNode.
• DoFooNode thusly returns its own providedValues instead of that of a parent DoFooNode.