feat: Refactor STFolderWatcher and fix warnings

Refactored the `checkFolderChanges` function in `STFolderWatcher.swift` to improve the logic for detecting file changes, additions, and deletions. This new implementation correctly handles file modifications and prevents them from being misidentified as deletions.

Additionally, this commit resolves compiler warnings in `STFolderTests.swift` by removing unused variable assignments, ensuring a cleaner and more efficient test suite.

Author: linhay

Sources/STFilePath/STFolderWatcher.swift

@@ -147,30 +147,30 @@ public class STFolderWatcher {
         _stream = nil
     }
 
-    // Private Method to Check Folder Changes
     private func checkFolderChanges() {
         do {
-            let files = try folder.allSubFilePaths().compactMap(\.asFile)
-            
-            for file in files {
-                if let modificationDate = previousContents[file] {
-                    if file.attributes.modificationDate != modificationDate {
-                        let change = Changed(kind: .changed, file: file)
-                        continuation?.yield(change)
+            let currentFiles = try folder.allSubFilePaths().compactMap(\.asFile)
+            let currentFilesSet = Set(currentFiles)
+            let previousFilesSet = Set(previousContents.keys)
+
+            // Check for deletions
+            for file in previousFilesSet.subtracting(currentFilesSet) {
+                continuation?.yield(Changed(kind: .deleted, file: file))
+                previousContents.removeValue(forKey: file)
+            }
+
+            // Check for additions and modifications
+            for file in currentFiles {
+                if let oldModificationDate = previousContents[file] {
+                    if file.attributes.modificationDate != oldModificationDate {
+                        continuation?.yield(Changed(kind: .changed, file: file))
                         previousContents[file] = file.attributes.modificationDate
                     }
                 } else {
-                    let change = Changed(kind: .added, file: file)
-                    continuation?.yield(change)
+                    continuation?.yield(Changed(kind: .added, file: file))
                     previousContents[file] = file.attributes.modificationDate
                 }
             }
-            
-            Set(previousContents.keys).subtracting(files).forEach { file in
-                let change = Changed(kind: .deleted, file: file)
-                continuation?.yield(change)
-                previousContents[file] = nil
-            }
         } catch {
             continuation?.finish(throwing: error)
         }

Tests/STFilePathTests/STFolderTests.swift

@@ -36,8 +36,8 @@ struct STFolderTests {
         let testFolder = try createTestFolder()
         try testFolder.create()
         let subfolder = try testFolder.create(folder: "subfolder")
-        let file1 = try testFolder.create(file: "file1.txt")
-        let file2 = try subfolder.create(file: "file2.txt")
+        try testFolder.create(file: "file1.txt")
+        try subfolder.create(file: "file2.txt")
         try testFolder.create(file: ".hidden.txt")
 
         let allPaths = try testFolder.allSubFilePaths()