Fix CachedEnvironment attribute cache issue (#313)

Author: Kyle-Ye

Package.resolved

@@ -1,13 +1,13 @@
 {
-  "originHash" : "669d1f5a7baa4f6093075d288ac99f536ebb7801497e931b763050191ecbf7d0",
+  "originHash" : "c6403e6357703cd6a416b17852a4312a975c4f5a164d0170118352abe1be3e2d",
   "pins" : [
     {
       "identity" : "darwinprivateframeworks",
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/OpenSwiftUIProject/DarwinPrivateFrameworks.git",
       "state" : {
         "branch" : "main",
-        "revision" : "88f975a6b211a5c9b3f2c26e55079b7d8f40275b"
+        "revision" : "ad18bd6feaa29e9b138ff7823796c6bc76295fb7"
       }
     },
     {
@@ -25,7 +25,7 @@
       "location" : "https://github.com/OpenSwiftUIProject/OpenGraph",
       "state" : {
         "branch" : "main",
-        "revision" : "fed93356e5876f1fc1ae452a9a799e481c8ea170"
+        "revision" : "cc2df5ac75d32f33fb6906b4abfbe18114138c91"
       }
     },
     {

Sources/OpenSwiftUICore/Data/Environment/CachedEnvironment.swift

@@ -46,11 +46,12 @@ package struct CachedEnvironment {
         self.platformCache = PlatformCache()
     }
 
-    package mutating func attribute<T>(id: CachedEnvironment.ID, _ body: (EnvironmentValues) -> T) -> Attribute<T> {
+    package mutating func attribute<T>(id: CachedEnvironment.ID, _ body: @escaping (EnvironmentValues) -> T) -> Attribute<T> {
         guard let item = mapItems.first(where: { $0.key == id }) else {
-            // Blocked by OG's Map
-            // preconditionFailure("TODO")
-            return Attribute(value: body(environment.value))
+            let map = Map(environment, body)
+            let attribute = Attribute(map)
+            mapItems.append(MapItem(key: id, value: attribute.identifier))
+            return attribute
         }
         return item.value.unsafeCast(to: T.self)
     }

Sources/OpenSwiftUICore/Graph/GraphInputs.swift

@@ -154,7 +154,7 @@ public struct _GraphInputs {
         preconditionFailure("TODO")
     }
 
-    package func mapEnvironment<T>(id: CachedEnvironment.ID, _ body: (EnvironmentValues) -> T) -> Attribute<T> {
+    package func mapEnvironment<T>(id: CachedEnvironment.ID, _ body: @escaping (EnvironmentValues) -> T) -> Attribute<T> {
         cachedEnvironment.wrappedValue.attribute(id: id, body)
     }
 

Sources/OpenSwiftUICore/View/Input/ViewInputs.swift

@@ -170,7 +170,7 @@ public struct _ViewInputs {
         )
     }
 
-    package func mapEnvironment<T>(id: CachedEnvironment.ID, _ body: (EnvironmentValues) -> T) -> Attribute<T> {
+    package func mapEnvironment<T>(id: CachedEnvironment.ID, _ body: @escaping (EnvironmentValues) -> T) -> Attribute<T> {
         base.mapEnvironment(id: id, body)
     }
 

Tests/OpenSwiftUICoreTests/Data/Environment/CachedEnvironmentTests.swift

@@ -0,0 +1,24 @@
+//
+//  CachedEnvironmentTests.swift
+//  OpenSwiftUICoreTests
+
+import OpenGraphShims
+@_spi(ForOpenSwiftUIOnly) import OpenSwiftUICore
+@testable import OpenSwiftUICore
+import OpenSwiftUITestsSupport
+import Testing
+
+@MainActor
+struct CachedEnvironmentTests {
+    @Test
+    func attribute() {
+        let graph = Graph(shared: Graph())
+        let globalSubgraph = Subgraph(graph: graph)
+        Subgraph.current = globalSubgraph
+        defer { Subgraph.current = nil }
+        var env = CachedEnvironment(.init(value: .init()))
+        let attribute1 = env.attribute(id: .layoutDirection) { $0.layoutDirection }
+        let attribute2 = env.attribute(id: .layoutDirection) { $0.layoutDirection }
+        #expect(attribute1 == attribute2)
+    }
+}