Fix FileManager's extended attribute symlink handling

Sources/FoundationEssentials/FileManager/FileManager+Files.swift

@@ -522,21 +522,21 @@ extension _FileManagerImpl {
 
     private func _extendedAttributes(at path: UnsafePointer<CChar>, followSymlinks: Bool) throws -> [String : Data]? {
         #if canImport(Darwin)
-        var size = listxattr(path, nil, 0, 0)
+        var size = listxattr(path, nil, 0, followSymlinks ? 0 : XATTR_NOFOLLOW)
         #elseif os(FreeBSD)
         var size = (followSymlinks ? extattr_list_file : extattr_list_link)(path, EXTATTR_NAMESPACE_USER, nil, 0)
         #else
-        var size = listxattr(path, nil, 0)
+        var size = followSymlinks ? listxattr(path, nil, 0) : llistxattr(path, nil, 0)
         #endif
         guard size > 0 else { return nil }
         let keyList = UnsafeMutableBufferPointer<CChar>.allocate(capacity: size)
         defer { keyList.deallocate() }
         #if canImport(Darwin)
-        size = listxattr(path, keyList.baseAddress!, size, 0)
+        size = listxattr(path, keyList.baseAddress!, size, followSymlinks ? 0 : XATTR_NOFOLLOW)
         #elseif os(FreeBSD)
-        size = (followSymlinks ? extattr_list_file : extattr_list_link)(path, EXTATTR_NAMESPACE_USER, nil, 0)
+        size = (followSymlinks ? extattr_list_file : extattr_list_link)(path, EXTATTR_NAMESPACE_USER, keyList.baseAddress!, size)
         #else
-        size = listxattr(path, keyList.baseAddress!, size)
+        size = followSymlinks ? listxattr(path, keyList.baseAddress!, size) : llistxattr(path, keyList.baseAddress!, size)
         #endif
         guard size > 0 else { return nil }
 
@@ -553,7 +553,7 @@ extension _FileManagerImpl {
             }
             #endif
 
-            if let value = try _extendedAttribute(current, at: path, followSymlinks: false) {
+            if let value = try _extendedAttribute(current, at: path, followSymlinks: followSymlinks) {
                 extendedAttrs[currentKey] = value
             }
         }

Sources/FoundationEssentials/FileManager/FileManager+Utilities.swift

@@ -193,15 +193,15 @@ extension _FileManagerImpl {
             #else
             var result: Int32
             if followSymLinks {
-                result = lsetxattr(path, key, buffer.baseAddress!, buffer.count, 0)
-            } else {
                 result = setxattr(path, key, buffer.baseAddress!, buffer.count, 0)
+            } else {
+                result = lsetxattr(path, key, buffer.baseAddress!, buffer.count, 0)
             }
             #endif
 
             #if os(macOS) && FOUNDATION_FRAMEWORK
-            // if setxaddr failed and its a permission error for a sandbox app trying to set quaratine attribute, ignore it since its not
-            // permitted, the attribute will be put on the file by the quaratine MAC hook
+            // if setxattr failed and its a permission error for a sandbox app trying to set quarantine attribute, ignore it since its not
+            // permitted, the attribute will be put on the file by the quarantine MAC hook
             if result == -1 && errno == EPERM && _xpc_runtime_is_app_sandboxed() && strcmp(key, "com.apple.quarantine") == 0 {
                 return
             }

Tests/FoundationEssentialsTests/FileManager/FileManagerTests.swift

@@ -1046,6 +1046,60 @@ private struct FileManagerTests {
         }
     }
 
+    // Extended attributes are not supported on all platforms
+    #if !os(Windows) && !os(WASI) && !os(OpenBSD) && !canImport(Android)
+    @Test func extendedAttributesOnSymlinks() async throws {
+        let xattrKey = FileAttributeKey("NSFileExtendedAttributes")
+        #if os(Linux)
+        // Linux requires the user.* namespace prefix for regular files
+        let attrName = "user.swift.foundation.symlinktest"
+        #else
+        let attrName = "org.swift.foundation.symlinktest"
+        #endif
+        let attrValue = Data([0xAA, 0xBB, 0xCC])
+        let attrValue2 = Data([0xDD, 0xEE, 0xFF])
+
+        try await FilePlayground {
+            File("target", contents: Data("payload".utf8))
+            SymbolicLink("link", destination: "target")
+        }.test { fileManager in
+            // First, validate that reading the attribute from the link does not read the value from the target
+            do {
+                try fileManager.setAttributes([xattrKey: [attrName: attrValue]], ofItemAtPath: "target")
+                let targetAttrs = try fileManager.attributesOfItem(atPath: "target")
+                let targetXAttrs = targetAttrs[xattrKey] as? [String: Data]
+                #expect(targetXAttrs?[attrName] == attrValue)
+
+                let linkAttrs = try fileManager.attributesOfItem(atPath: "link")
+                let linkXAttrs = linkAttrs[xattrKey] as? [String: Data]
+                #expect(linkXAttrs?[attrName] == nil)
+            }
+
+            // Attempt to set xattrs on the symlink
+            #if os(Linux)
+            // On Linux, user xattrs cannot be set on symlinks
+            #expect(throws: CocoaError.self) {
+                try fileManager.setAttributes([xattrKey: [attrName: attrValue2]], ofItemAtPath: "link")
+            }
+            let expectedValue: Data? = nil
+            #else
+            try fileManager.setAttributes([xattrKey: [attrName: attrValue2]], ofItemAtPath: "link")
+            let expectedValue: Data? = attrValue2
+            #endif
+
+            // Ensure that reading back the xattr of the link produces the expected value
+            let linkAttrs = try fileManager.attributesOfItem(atPath: "link")
+            let linkXAttrs = linkAttrs[xattrKey] as? [String: Data]
+            #expect(linkXAttrs?[attrName] == expectedValue)
+
+            // Ensure that setting the xattr on the link did not set the xattr on the target
+            let targetAttrs = try fileManager.attributesOfItem(atPath: "target")
+            let targetXAttrs = targetAttrs[xattrKey] as? [String: Data]
+            #expect(targetXAttrs?[attrName] == attrValue)
+        }
+    }
+    #endif
+
     #if !canImport(Darwin) || os(macOS)
     @Test func currentUserHomeDirectory() async throws {
         let userName = ProcessInfo.processInfo.userName