refactor: clean up retrieval from data transfer item

src/file-selector.spec.ts

@@ -312,13 +312,13 @@ it("should throw if reading file entry fails", (done) => {
     .catch(() => done());
 });
 
-it("should throw if DataTransferItem is not a File", (done) => {
+it("should throw if DataTransferItem is not a File", async () => {
   const item = dataTransferItem(null, "file");
-  const evt = dragEvtFromFilesAndItems([], [item]);
+  const event = dragEvtFromFilesAndItems([], [item]);
 
-  fromEvent(evt)
-    .then(() => done.fail("Getting the files should have failed"))
-    .catch(() => done());
+  await expect(fromEvent(event)).rejects.toThrow(
+    "Transferred item is not a file.",
+  );
 });
 
 it("should use getAsFileSystemHandle when available", async () => {
@@ -380,8 +380,11 @@ it("should not use getAsFileSystemHandle when not in a secure context", async ()
 });
 
 it("should reject when getAsFileSystemHandle resolves to null", async () => {
-  const evt = dragEvtFromItems([dataTransferItemWithFsHandle(null, null)]);
-  expect(fromEvent(evt)).rejects.toThrow("[object Object] is not a File");
+  const event = dragEvtFromItems([dataTransferItemWithFsHandle(null, null)]);
+
+  await expect(fromEvent(event)).rejects.toThrow(
+    "Transferred item is not a file.",
+  );
 });
 
 it("should fallback to getAsFile when getAsFileSystemHandle resolves to undefined", async () => {
@@ -410,6 +413,16 @@ it("should fallback to getAsFile when getAsFileSystemHandle resolves to undefine
   expect(file.path).toBe(`./${name}`);
 });
 
+it("should throw if getAsFileSystemHandle() does not return a file", async () => {
+  const file = createFile("test.json", {});
+  const handle = { kind: "unknown" } as unknown as FileSystemFileHandle;
+  const event = dragEvtFromItems([dataTransferItemWithFsHandle(file, handle)]);
+
+  await expect(fromEvent(event)).rejects.toThrow(
+    "Transferred item is not a file.",
+  );
+});
+
 function dragEvtFromItems(
   items: DataTransferItem | DataTransferItem[],
   type: string = "drop",
@@ -589,21 +602,18 @@ function createFileSystemFileHandle<T>(
   return [
     file,
     {
+      kind: "file",
       getFile() {
         return Promise.resolve(file);
       },
-    },
+    } as FileSystemFileHandle,
   ];
 }
 
 function sortFiles<T extends File>(files: T[]) {
   return files.slice(0).sort((a, b) => a.name.localeCompare(b.name));
 }
 
-interface FileSystemFileHandle {
-  getFile(): Promise<File | null>;
-}
-
 type FileOrDirEntry = FileEntry | DirEntry;
 
 interface FileEntry extends Entry {

src/file-selector.ts

@@ -108,34 +108,49 @@ function flatten<T>(items: any[]): T[] {
 async function fromDataTransferItem(
   item: DataTransferItem,
   entry?: FileSystemEntry | null,
-) {
-  // Check if we're in a secure context; due to a bug in Chrome (as far as we know) the browser crashes when calling this API (yet to be confirmed as a consistent behavior).
-  //
+): Promise<FileWithPath> {
+  const fileWithPath = await fromFileSystemHandle(item, entry);
+  if (fileWithPath) {
+    return fileWithPath;
+  }
+
+  const file = item.getAsFile();
+  if (!file) {
+    throw new Error("Transferred item is not a file.");
+  }
+  return toFileWithPath(file, entry?.fullPath);
+}
+
+async function fromFileSystemHandle(
+  item: PartialDataTransferItem,
+  entry?: FileSystemEntry | null,
+): Promise<File | null> {
+  // Check if we're in a secure context; due to a bug in Chrome (as far as we know)
+  // the browser crashes when calling this API (yet to be confirmed as a consistent behavior).
   // See:
   // - https://issues.chromium.org/issues/40186242
   // - https://github.com/react-dropzone/react-dropzone/issues/1397
+  // If the browser does not support the API act as if the file could not be retrieved.
   if (
-    globalThis.isSecureContext &&
-    typeof (item as any).getAsFileSystemHandle === "function"
+    !globalThis.isSecureContext ||
+    !(typeof item.getAsFileSystemHandle === "function")
   ) {
-    const h = await (item as any).getAsFileSystemHandle();
-    if (h === null) {
-      throw new Error(`${item} is not a File`);
-    }
-    // It seems that the handle can be `undefined` (see https://github.com/react-dropzone/file-selector/issues/120),
-    // so we check if it isn't; if it is, the code path continues to the next API (`getAsFile`).
-    if (h !== undefined) {
-      const file = await h.getFile();
-      file.handle = h;
-      return toFileWithPath(file);
-    }
+    return null;
   }
-  const file = item.getAsFile();
-  if (!file) {
-    throw new Error(`${item} is not a File`);
+
+  const handle = await item.getAsFileSystemHandle();
+
+  // The handle can be undefined due to a browser bug, in this case we act as if the file could not be retrieved.
+  // See: https://github.com/react-dropzone/file-selector/issues/120
+  if (handle === undefined) {
+    return null;
+  }
+
+  if (!handle || !isFileHandle(handle)) {
+    throw new Error("Transferred item is not a file.");
   }
-  const fwp = toFileWithPath(file, entry?.fullPath ?? undefined);
-  return fwp;
+
+  return toFileWithPath(await handle.getFile(), entry?.fullPath, handle);
 }
 
 async function fromEntry(
@@ -179,6 +194,10 @@ async function fromFileEntry(
   return fileWithPath;
 }
 
+const isFileHandle = (
+  handle: FileSystemHandle,
+): handle is FileSystemFileHandle => handle.kind === "file";
+
 const isDirectoryEntry = (
   entry: FileSystemEntry,
 ): entry is FileSystemDirectoryEntry => entry.isDirectory;
@@ -194,6 +213,14 @@ const readEntries = (
 ): Promise<FileSystemEntry[]> =>
   new Promise((resolve, reject) => reader.readEntries(resolve, reject));
 
+interface PartialDataTransferItem extends DataTransferItem {
+  // This method is not yet widely supported in all browsers, and is thus marked as optional.
+  // See: https://developer.mozilla.org/en-US/docs/Web/API/DataTransferItem/getAsFileSystemHandle
+  // Additionally, this method is known to return `undefined` in some cases due to browser bugs.
+  // See: https://github.com/react-dropzone/file-selector/issues/120
+  getAsFileSystemHandle?(): Promise<FileSystemHandle | null | undefined>;
+}
+
 // Infinite type recursion
 // https://github.com/Microsoft/TypeScript/issues/3496#issuecomment-128553540
 interface FileArray extends Array<FileValue> {}