Update ViewAlias

Author: Kyle-Ye

Sources/OpenSwiftUI/View/ViewAlias.swift

@@ -0,0 +1,253 @@
+//
+//  ViewAlias.swift
+//  OpenSwiftUI
+//
+//  Audited for iOS 18.0
+//  Status: Complete
+//  ID: D9F7AF928092578A4B8FA861B49E2161 (SwiftUI)
+
+import OpenGraphShims
+@_spi(ForOpenSwiftUIOnly) import OpenSwiftUICore
+
+// MARK: - ViewAlias
+
+protocol ViewAlias: PrimitiveView {
+    init()
+}
+
+// MARK: - View + ViewAlias Extension
+
+extension View {
+    func viewAlias<Alias, Source>(
+        _ alias: Alias.Type,
+        _ source: () -> Source
+    ) -> some View where Alias: ViewAlias, Source: View {
+        modifier(StaticSourceWriter<Alias, Source>(source: source()))
+    }
+
+    func viewAlias<Predicate, Alias, Source>(
+        if predicate: Predicate.Type,
+        _ alias: Alias.Type,
+        _ source: () -> Source
+    ) -> some View where Predicate: ViewInputPredicate, Alias: ViewAlias, Source: View {
+        modifier(StaticSourceWriter<Alias, Source>(source: source()).requiring(predicate))
+    }
+
+    func optionalViewAlias<Alias, Source>(
+        _ alias: Alias.Type,
+        _ source: () -> Source?
+    ) -> some View where Alias: ViewAlias, Source: View {
+        modifier(OptionalSourceWriter<Alias, Source>(source: source()))
+    }
+}
+
+// MARK: - AnySourceFormula
+
+private protocol AnySourceFormula {
+    static func makeView<Alias>(
+        view: _GraphValue<Alias>,
+        source: AnySource,
+        inputs: _ViewInputs
+    ) -> _ViewOutputs where Alias: ViewAlias
+
+    static func makeViewList<Alias>(
+        view: _GraphValue<Alias>,
+        source: AnySource,
+        inputs: _ViewListInputs
+    ) -> _ViewListOutputs where Alias: ViewAlias
+
+    static func viewListCount(
+        source: AnySource,
+        inputs: _ViewListCountInputs
+    ) -> Int?
+}
+
+// MARK: - OptionalViewAlias
+
+struct OptionalViewAlias<Alias>: DynamicProperty where Alias: ViewAlias {
+    static func _makeProperty<Value>(in buffer: inout _DynamicPropertyBuffer, container: _GraphValue<Value>, fieldOffset: Int, inputs: inout _GraphInputs) {
+        if let source = inputs[SourceInput<Alias>.self].top {
+            if let valueIsNil = source.valueIsNil {
+                let box = OptionalSourceBox(sourceIsNil: valueIsNil)
+                buffer.append(box, fieldOffset: fieldOffset)
+            } else {
+                let box = StaticSourceBox(sourceExists: true)
+                buffer.append(box, fieldOffset: fieldOffset)
+            }
+        } else {
+            let box = StaticSourceBox(sourceExists: false)
+            buffer.append(box, fieldOffset: fieldOffset)
+        }
+    }
+
+    var sourceExists: Bool
+
+    var wrappedValue: Alias? {
+        sourceExists ? Alias() : nil
+    }
+
+    private struct OptionalSourceBox: DynamicPropertyBox {
+        @Attribute var sourceIsNil: Bool
+
+        func update(property: inout OptionalViewAlias, phase: ViewPhase) -> Bool {
+            let (sourceIsNil, changed) = $sourceIsNil.changedValue()
+            property.sourceExists = !sourceIsNil
+            return changed
+        }
+    }
+
+    private struct StaticSourceBox: DynamicPropertyBox {
+        var sourceExists: Bool
+
+        func update(property: inout OptionalViewAlias, phase: ViewPhase) -> Bool {
+            property.sourceExists = sourceExists
+            return false
+        }
+    }
+}
+
+// MARK: - OptionalSourceWriter
+
+private struct OptionalSourceWriter<Alias, Source>: PrimitiveViewModifier, _GraphInputsModifier where Alias: ViewAlias, Source: View {
+    var source: Source?
+
+    static func _makeInputs(modifier: _GraphValue<Self>, inputs: inout _GraphInputs) {
+        inputs.append(
+            AnySource(modifier.value[offset: { .of(&$0.source) }]),
+            to: SourceInput<Alias>.self
+        )
+    }
+}
+
+// MARK: - StaticSourceWriter
+
+private struct StaticSourceWriter<Alias, Source>: PrimitiveViewModifier, _GraphInputsModifier where Alias: ViewAlias, Source: View {
+    var source: Source
+
+    static func _makeInputs(modifier: _GraphValue<Self>, inputs: inout _GraphInputs) {
+        inputs.append(
+            AnySource(modifier.value[offset: { .of(&$0.source) }]),
+            to: SourceInput<Alias>.self
+        )
+    }
+}
+
+// MARK: - SourceFormula
+
+private struct SourceFormula<Source>: AnySourceFormula where Source: View {
+    static func makeView<Alias>(
+        view: _GraphValue<Alias>,
+        source: AnySource,
+        inputs: _ViewInputs
+    ) -> _ViewOutputs where Alias: ViewAlias {
+        guard let attribute = source.value.attribute else {
+            return .init()
+        }
+        return if source.valueIsNil == nil {
+            Optional<Source>.makeDebuggableView(
+                view: _GraphValue(Attribute(identifier: attribute)),
+                inputs: inputs
+            )
+        } else {
+            Source.makeDebuggableView(
+                view: _GraphValue(Attribute(identifier: attribute)),
+                inputs: inputs
+            )
+        }
+    }
+
+    static func makeViewList<Alias>(
+        view: _GraphValue<Alias>,
+        source: AnySource,
+        inputs: _ViewListInputs
+    ) -> _ViewListOutputs where Alias: ViewAlias {
+        guard let attribute = source.value.attribute else {
+            return .emptyViewList(inputs: inputs)
+        }
+        return if source.valueIsNil == nil {
+            Optional<Source>.makeDebuggableViewList(
+                view: _GraphValue(Attribute(identifier: attribute)),
+                inputs: inputs
+            )
+        } else {
+            Source.makeDebuggableViewList(
+                view: _GraphValue(Attribute(identifier: attribute)),
+                inputs: inputs
+            )
+        }
+    }
+
+    static func viewListCount(
+        source: AnySource,
+        inputs: _ViewListCountInputs
+    ) -> Int? {
+        if source.valueIsNil == nil {
+            Optional<Source>._viewListCount(inputs: inputs)
+        } else {
+            Source._viewListCount(inputs: inputs)
+        }
+    }
+}
+
+// MARK: - AnySource
+
+private struct AnySource: GraphReusable {
+    let formula: AnySourceFormula.Type
+    var value: AnyWeakAttribute
+    let valueIsNil: Attribute<Bool>?
+
+    init<V>(_ view: Attribute<V>) where V: View {
+        formula = SourceFormula<V>.self
+        value = AnyWeakAttribute(view.identifier)
+        valueIsNil = nil
+    }
+
+    init<V>(_ view: Attribute<V?>) where V: View {
+        formula = SourceFormula<V?>.self
+        value = AnyWeakAttribute(view.identifier)
+        valueIsNil = Attribute(isNil(input: view))
+    }
+
+    struct isNil<Input>: Rule, AsyncAttribute {
+        @Attribute
+        var input: Input?
+
+        var value: Bool { input == nil }
+    }
+
+    mutating func makeReusable(indirectMap: IndirectAttributeMap) {
+        guard let attribute = value.attribute else {
+            return
+        }
+        if let result = indirectMap.map[attribute] {
+            value = AnyWeakAttribute(result)
+        } else {
+            let indirect = indirectMap.subgraph.apply {
+                attribute.createIndirect()
+            }
+            indirectMap.map[attribute] = indirect
+            value = AnyWeakAttribute(indirect)
+        }
+    }
+
+    func tryToReuse(by other: AnySource, indirectMap: IndirectAttributeMap, testOnly: Bool) -> Bool {
+        guard formula == other.formula,
+              let attribute = value.attribute,
+              let result = indirectMap.map[attribute],
+              let otherAttribute = other.value.attribute
+        else {
+            ReuseTrace.traceNeverMadeReusableFailure(AnySource.self)
+            return false
+        }
+        if !testOnly {
+            result.source = otherAttribute
+        }
+        return true
+    }
+}
+
+// MARK: - SourceInput
+
+private struct SourceInput<Alias>: ViewInput where Alias: ViewAlias {
+    static var defaultValue: Stack<AnySource> { Stack() }
+}