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Merged
Kyle-Ye merged 2 commits into from
Jan 25, 2026
Merged

Add DebugReplaceableView and CustomViewCountCache API #747

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d27dfba
Optimize OPENSWIFTUI_SUPPORT_2025_API code
Kyle-Ye Jan 25, 2026
9f88ddc
Add DebugReplaceableView API
Kyle-Ye Jan 25, 2026
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2 changes: 1 addition & 1 deletion Sources/OpenSwiftUICore/Data/Combine/ObservedObject.swift
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Expand Up @@ -211,7 +211,7 @@ public struct ObservedObject<ObjectType>: DynamicProperty where ObjectType: Obse

@available(OpenSwiftUI_v1_0, *)
extension ObservedObject {
#if OPENSWIFTUI_RELEASE_2025 // Audited for 7.0.67
#if OPENSWIFTUI_SUPPORT_2025_API // Audited for 7.0.67
nonisolated static func makeBoxAndSignal<V>(
in buffer: inout _DynamicPropertyBuffer,
container: _GraphValue<V>,
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2 changes: 1 addition & 1 deletion Sources/OpenSwiftUICore/Data/Combine/StateObject.swift
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Expand Up @@ -338,7 +338,7 @@ public struct StateObject<ObjectType>: DynamicProperty where ObjectType: Observa
inputs: inout _GraphInputs
) {
var buf = _DynamicPropertyBuffer()
#if OPENSWIFTUI_RELEASE_2025
#if OPENSWIFTUI_SUPPORT_2025_API
let attribute = ObservedObject<ObjectType>.makeBoxAndSignal(in: &buf, container: container, fieldOffset: 0)
buffer.append(Box(links: buf, object: nil), fieldOffset: fieldOffset)
addTreeValue(
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7 changes: 7 additions & 0 deletions Sources/OpenSwiftUICore/Modifier/CustomViewModifier.swift
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Expand Up @@ -62,7 +62,12 @@ public struct PlaceholderContentView<Value>: View {
}

nonisolated public static func _viewListCount(inputs: _ViewListCountInputs) -> Int? {
#if OPENSWIFTUI_SUPPORT_2025_API
// TODO: inputs.cachedViewListCount(type: Self.self)
return nil
#else
providerViewListCount(inputs: inputs)
#endif
}

public typealias Body = Never
Expand Down Expand Up @@ -218,6 +223,7 @@ extension ViewModifierContentProvider {
}
}

#if !OPENSWIFTUI_SUPPORT_2025_API
nonisolated fileprivate static func providerViewListCount(
inputs: _ViewListCountInputs
) -> Int? {
Expand All @@ -231,6 +237,7 @@ extension ViewModifierContentProvider {
inputs.customModifierTypes.append(ObjectIdentifier(Self.self))
return input(inputs)
}
#endif
}

extension _GraphInputs {
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196 changes: 196 additions & 0 deletions Sources/OpenSwiftUICore/View/DynamicView/DebugReplaceableView.swift
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@@ -0,0 +1,196 @@
//
// DebugReplaceableView.swift
// OpenSwiftUICore
//
// Audited for 7.2.5
// Status: Complete
// ID: 8F31ED3737048FE14E730EE04503F67D (SwiftUICore)

#if OPENSWIFTUI_SUPPORT_2025_API
package import OpenAttributeGraphShims

// MARK: - DebugReplaceableView

/// Erases view opaque result types in debug builds.
///
/// You don't use this type directly. Instead OpenSwiftUI creates this type on
/// your behalf when building in debug mode.
///
/// When in debug builds, OpenSwiftUI will erase all opaque result types to
/// `DebugReplaceableView`. This allows developer tools, such as Xcode Previews,
/// to replace the definition of the view without fully rebuilding.
///
/// As such, seeing this type in traces and the view debugger is expected when
/// building for debugging. This type erasure can impact performance, especially
/// when dealing with dynamic content (like content generated by a ForEach, or
/// List) so any performance testing should be done in release mode.
///
/// This type acts similarly to an `AnyView` in that it type-erases its content,
/// however it depends on the underlying type of the value not actually changing
/// as it is in place of an opaque result type. As such, it *should not be used
/// in app code*.
@available(OpenSwiftUI_v7_0, *)
public struct DebugReplaceableView: View, PrimitiveView {
var storage: DebugReplaceableViewStorageBase

/// Creates a debug replaceable view erasing the given view.
///
/// You don't use this initializer directly. Instead OpenSwiftUI creates this
/// type on your behalf when building in debug mode.
///
/// This type acts similarly to an `AnyView` in that it type-erases its
/// content, however it depends on the underlying type of the value not
/// actually changing as it is in place of an opaque result type. As such,
/// it *should not be used in app code*.
@available(*, deprecated, message: "DebugReplaceableView should not be used directly, to type erase a View, you should use AnyView.")
@_alwaysEmitIntoClient
public init<V>(erasing view: V) where V: View {
self.init(_erasing: view)
}

@usableFromInline
internal init<V>(_erasing view: V) where V: View {
if let replaceableView = view as? DebugReplaceableView {
storage = replaceableView.storage
} else {
storage = DebugReplaceableViewStorage(view: view)
}
}

nonisolated public static func _makeView(view: _GraphValue<Self>, inputs: _ViewInputs) -> _ViewOutputs {
makeDynamicView(metadata: (), view: view, inputs: inputs)
}

nonisolated public static func _makeViewList(view: _GraphValue<Self>, inputs: _ViewListInputs) -> _ViewListOutputs {
makeDynamicViewList(metadata: (), view: view, inputs: inputs)
}

@available(OpenSwiftUI_v2_0, *)
nonisolated public static func _viewListCount(inputs: _ViewListCountInputs) -> Int? {
let info = inputs.debugReplaceableViewInfo
if info.countAsZero, let countedAsZero = info.countedAsZero {
countedAsZero.pointee = true
}
return info.countAsZero ? 0 : nil
}

package func visitContent<Visitor: ViewVisitor>(_ visitor: inout Visitor) {
storage.visitContent(&visitor)
}

}
@available(*, unavailable)
extension DebugReplaceableView: Sendable {}

// MARK: - DebugReplaceableView: DynamicView

extension DebugReplaceableView: DynamicView {
package static var canTransition: Bool { false }

package func childInfo(metadata: ()) -> (any Any.Type, UniqueID?) {
(storage.childType, nil)
}

package func makeChildView(metadata: (), view: Attribute<DebugReplaceableView>, inputs: _ViewInputs) -> _ViewOutputs {
storage.makeChildView(view: view, inputs: inputs)
}

package func makeChildViewList(metadata: (), view: Attribute<DebugReplaceableView>, inputs: _ViewListInputs) -> _ViewListOutputs {
storage.makeChildViewList(view: view, inputs: inputs)
}
}

// MARK: - DebugReplaceableViewStorageBase

@available(OpenSwiftUI_v7_0, *)
@usableFromInline
internal class DebugReplaceableViewStorageBase {
fileprivate var childType: any Any.Type {
_openSwiftUIBaseClassAbstractMethod()
}

fileprivate func makeChildView(view: Attribute<DebugReplaceableView>, inputs: _ViewInputs) -> _ViewOutputs {
_openSwiftUIBaseClassAbstractMethod()
}

fileprivate func makeChildViewList(view: Attribute<DebugReplaceableView>, inputs: _ViewListInputs) -> _ViewListOutputs {
_openSwiftUIBaseClassAbstractMethod()
}

fileprivate func visitContent<Visitor>(_ visitor: inout Visitor) where Visitor: ViewVisitor {
_openSwiftUIBaseClassAbstractMethod()
}
}

@available(*, unavailable)
extension DebugReplaceableViewStorageBase: Sendable {}

// MARK: - DebugReplaceableViewStorage

private final class DebugReplaceableViewStorage<V>: DebugReplaceableViewStorageBase where V: View {
let view: V

init(view: V) {
self.view = view
super.init()
}

override var childType: any Any.Type {
V.self
}

override func makeChildView(
view: Attribute<DebugReplaceableView>,
inputs: _ViewInputs
) -> _ViewOutputs {
var inputs = inputs
inputs.base.pushStableType(V.self)
let childView = Attribute(DebugReplaceableViewChild<V>(view: view))
childView.value = self.view
return V.makeDebuggableView(view: _GraphValue(childView), inputs: inputs)
}

override func makeChildViewList(
view: Attribute<DebugReplaceableView>,
inputs: _ViewListInputs
) -> _ViewListOutputs {
var inputs = inputs
inputs.base.pushStableType(V.self)
let childView = Attribute(DebugReplaceableViewChild<V>(view: view))
childView.value = self.view
return V.makeDebuggableViewList(view: _GraphValue(childView), inputs: inputs)
}

override func visitContent<Visitor>(_ visitor: inout Visitor) where Visitor : ViewVisitor {
visitor.visit(view)
}
}

// MARK: - DebugReplaceableViewInfo

package struct DebugReplaceableViewInfo {
package var countAsZero: Bool
package var countedAsZero: UnsafeMutablePointer<Bool>?

package init(countAsZero: Bool, countedAsZero: UnsafeMutablePointer<Bool>?) {
self.countAsZero = countAsZero
self.countedAsZero = countedAsZero
}
}

// MARK: - DebugReplaceableViewChild

fileprivate struct DebugReplaceableViewChild<V>: StatefulRule, AsyncAttribute, CustomStringConvertible where V: View {
@Attribute var view: DebugReplaceableView

typealias Value = V

func updateValue() {
value = (view.storage as! DebugReplaceableViewStorage<V>).view
}

var description: String {
"\(V.self)"
}
}
#endif
2 changes: 1 addition & 1 deletion Sources/OpenSwiftUICore/View/DynamicView/DynamicView.swift
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Expand Up @@ -12,7 +12,7 @@ package protocol DynamicView {
static var canTransition: Bool { get }
static var traitKeysDependOnView: Bool { get }
associatedtype Metadata
associatedtype ID : Hashable
associatedtype ID: Hashable
static func makeID() -> ID
func childInfo(metadata: Metadata) -> (any Any.Type, ID?)
func makeChildView(metadata: Metadata, view: Attribute<Self>, inputs: _ViewInputs) -> _ViewOutputs
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98 changes: 98 additions & 0 deletions Sources/OpenSwiftUICore/View/Input/CustomViewCountCache.swift
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@@ -0,0 +1,98 @@
//
// CustomViewCountCache.swift
// OpenSwiftUICore
//
// Audited for 7.2.5
// Status: Complete
// ID: EB1EEB38755A34D46BFF2AE8785813E0 (SwiftUICore)

#if OPENSWIFTUI_SUPPORT_2025_API
import OpenAttributeGraphShims

/// A cache for tracking custom view counts during view list enumeration.
///
/// This cache stores count information for custom views, allowing efficient
/// lookups during view list traversal without recomputing counts.
package struct CustomViewCountCache {

/// Pointer to the head of a linked list of count entries
private var counts: UnsafeMutablePointer<Count>

/// Optional modifier options that affect how counts are computed
private var modifierOptions: ModifierOptions?

/// Updates the modifier options based on new inputs and a previous ID.
///
/// This method synchronizes the cache's options with the current view list
/// inputs, ensuring that count computations remain consistent.
///
/// - Parameters:
/// - inputs: The current view list count inputs
/// - previousID: The unique ID from the previous update
private mutating func updateOptions(inputs: _ViewListCountInputs, previousID: UniqueID) {
if let modifierOptions {
if modifierOptions.inputID == previousID {
self.modifierOptions = .init(
options: modifierOptions.options,
baseOptions: modifierOptions.baseOptions,
inputID: inputs.customInputs.id
)
}
} else {
self.modifierOptions = .init(
options: inputs.options,
baseOptions: inputs.baseOptions,
inputID: inputs.customInputs.id
)
}
}

// MARK: - CustomViewCountCache.ModifierOptions

/// Options that affect modifier behavior during count computation.
private struct ModifierOptions {
/// View list-specific options
let options: _ViewListInputs.Options

/// Base graph input options
let baseOptions: _GraphInputs.Options

/// Unique identifier for this set of inputs
var inputID: UniqueID

init(options: _ViewListInputs.Options, baseOptions: _GraphInputs.Options, inputID: UniqueID) {
self.options = options
self.baseOptions = baseOptions
self.inputID = inputID
}
}

// MARK: - CustomViewCountCache.Count

/// A node in the linked list of cached counts for custom views.
private struct Count {
/// The type identifier for the cached view
var id: ObjectIdentifier

/// The cached count value.
///
/// This is a double-optional:
/// - `nil`: Not yet computed
/// - `.some(nil)`: Explicitly has no static count (dynamic)
/// - `.some(.some(n))`: Has a static count of n
var count: Int??

/// Pointer to the next count node in the linked list, or nil if this is the last node
let next: UnsafeMutablePointer<Count>?

init(id: ObjectIdentifier, count: Int?? = nil, next: UnsafeMutablePointer<Count>? = nil) {
self.id = id
self.count = count
self.next = next
}
}
}

@available(*, unavailable)
extension CustomViewCountCache: Sendable {}
#endif
13 changes: 13 additions & 0 deletions Sources/OpenSwiftUICore/View/Input/ViewList.swift
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Expand Up @@ -112,13 +112,26 @@ public struct _ViewListCountInputs {
package var customInputs: PropertyList
package var options: _ViewListInputs.Options
package var baseOptions: _GraphInputs.Options
#if OPENSWIFTUI_SUPPORT_2025_API
package var customViewCache: CustomViewCountCache?
package var debugReplaceableViewInfo: DebugReplaceableViewInfo
#else
package var customModifierTypes: [ObjectIdentifier]
#endif

package init(_ inputs: _ViewListInputs) {
customInputs = inputs.base.customInputs
options = inputs.options
baseOptions = inputs.base.options
#if OPENSWIFTUI_SUPPORT_2025_API
customViewCache = nil
debugReplaceableViewInfo = DebugReplaceableViewInfo(
countAsZero: false,
countedAsZero: nil
)
#else
customModifierTypes = []
#endif
}

package subscript<T>(input: T.Type) -> T.Value where T: GraphInput {
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2 changes: 1 addition & 1 deletion Sources/OpenSwiftUICore/View/InterfaceIdiom/InterfaceIdiom.swift
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Expand Up @@ -6,7 +6,7 @@
// Status: Complete
// ID: 39057DDA72E946BD17E1F42CCA55F7F6 (SwiftUICore)

#if OPENSWIFTUI_RELEASE_2024
#if OPENSWIFTUI_SUPPORT_2024_API

// MARK: - InterfaceIdiom

Expand Down
2 changes: 1 addition & 1 deletion Sources/OpenSwiftUICore/View/InterfaceIdiom/InterfaceIdiomPredicate.swift
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Expand Up @@ -5,7 +5,7 @@
// Audited for 6.0.87
// Status: Complete

#if OPENSWIFTUI_RELEASE_2024
#if OPENSWIFTUI_SUPPORT_2024_API
package struct InterfaceIdiomPredicate<Idiom>: ViewInputPredicate where Idiom: InterfaceIdiom {
package init() {}

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