(140368780) Enable client iteration of AttributeScopes (#1093)

Author: jmschonfeld

Sources/FoundationEssentials/AttributedString/AttributeScope.swift

@@ -172,7 +172,7 @@ internal func _loadDefaultAttributes() -> [String : any AttributedStringKey.Type
 
 // TODO: Support AttributeScope key finding in FoundationPreview
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
-internal extension AttributeScope {
+extension AttributeScope {
     private static var scopeDescription: ScopeDescription {
         if let cached = _loadedScopeCache.withLock({ $0[Self.self] }) {
             return cached
@@ -198,13 +198,17 @@ internal extension AttributeScope {
         return desc
     }
 
-    static func attributeKeyTypes() -> [String : any AttributedStringKey.Type] {
+    internal static func attributeKeyTypes() -> [String : any AttributedStringKey.Type] {
         Self.scopeDescription.attributes
     }
 
-    static func markdownKeyTypes() -> [String : any MarkdownDecodableAttributedStringKey.Type] {
+    internal static func markdownKeyTypes() -> [String : any MarkdownDecodableAttributedStringKey.Type] {
         Self.scopeDescription.markdownAttributes
     }
+    
+    @available(FoundationPreview 6.2, *)
+    public static var attributeKeys: some Sequence<any AttributedStringKey.Type> {
+        Self.scopeDescription.attributes.values
+    }
 }
-
 #endif // FOUNDATION_FRAMEWORK

Tests/FoundationEssentialsTests/AttributedString/AttributedStringTests.swift

@@ -2427,6 +2427,22 @@ E {
 
         XCTAssertEqual(AttributedString(str[range], including: None.self), AttributedString("BC"))
     }
+    
+    func testScopeIterationAPI() {
+        struct TestScope : AttributeScope {
+            let testInt: AttributeScopes.TestAttributes.TestIntAttribute
+            let testBool: AttributeScopes.TestAttributes.TestBoolAttribute
+        }
+        
+        let testNames = TestScope.attributeKeys.map { $0.name }.sorted()
+        XCTAssertEqual(testNames, [AttributeScopes.TestAttributes.TestBoolAttribute.name, AttributeScopes.TestAttributes.TestIntAttribute.name].sorted())
+        
+        struct EmptyScope : AttributeScope {
+            
+        }
+        var emptyIterator = EmptyScope.attributeKeys.makeIterator()
+        XCTAssertNil(emptyIterator.next())
+    }
 #endif // FOUNDATION_FRAMEWORK
 
     func testAssignDifferentSubstring() {