refactor: strengthen upload boundary types

components/upload/FolderDropzone.tsx

@@ -28,12 +28,22 @@ function readDirectoryEntries(reader: FileSystemDirectoryReader) {
   })
 }
 
+function isFileEntry(entry: FileSystemEntry): entry is FileSystemFileEntry {
+  return entry.isFile
+}
+
+function isDirectoryEntry(entry: FileSystemEntry): entry is FileSystemDirectoryEntry {
+  return entry.isDirectory
+}
+
 async function collectEntryFiles(entry: FileSystemEntry): Promise<File[]> {
-  if (entry.isFile) {
-    return [await readDroppedFile(entry as FileSystemFileEntry)]
+  if (isFileEntry(entry)) {
+    return [await readDroppedFile(entry)]
   }
 
-  const reader = (entry as FileSystemDirectoryEntry).createReader()
+  if (!isDirectoryEntry(entry)) return []
+
+  const reader = entry.createReader()
   const files: File[] = []
 
   while (true) {
@@ -109,7 +119,8 @@ export default function FolderDropzone({
   }
 
   const handleDragLeave = (e: React.DragEvent<HTMLDivElement>) => {
-    if (!e.currentTarget.contains(e.relatedTarget as Node | null)) {
+    const relatedTarget = e.relatedTarget
+    if (!(relatedTarget instanceof Node) || !e.currentTarget.contains(relatedTarget)) {
       setIsDragActive(false)
     }
   }
@@ -127,7 +138,7 @@ export default function FolderDropzone({
         .map((item) => item.webkitGetAsEntry?.())
         .filter((entry): entry is FileSystemEntry => entry !== null)
 
-      const directoryEntries = rootEntries.filter((entry) => entry.isDirectory)
+      const directoryEntries = rootEntries.filter(isDirectoryEntry)
 
       if (directoryEntries.length > 0) {
         if (directoryEntries.length > 1) {
@@ -135,7 +146,7 @@ export default function FolderDropzone({
           return
         }
 
-        const rootEntry = directoryEntries[0] as FileSystemDirectoryEntry
+        const rootEntry = directoryEntries[0]
         const files = await collectEntryFiles(rootEntry)
         processFiles(files, rootEntry.name)
         return