From 06934f02ced38989d3e300f5bd2c34dde87bc767 Mon Sep 17 00:00:00 2001
From: Roland Groza <roland.groza@mujin.co.jp>
Date: Sat, 11 Jul 2026 15:44:29 +0900
Subject: [PATCH] feat: use a custom error when items are not files

Throw a dedicated UnexpectedObjectError (carrying the offending
DataTransferItem) instead of a generic Error that stringified to the
useless "[object Object] is not a File".
---
 .oxlintrc.json            |  4 +---
 src/error.spec.ts         | 17 +++++++++++++++++
 src/error.ts              |  8 ++++++++
 src/file-selector.spec.ts |  2 +-
 src/file-selector.ts      |  5 +++--
 5 files changed, 30 insertions(+), 6 deletions(-)
 create mode 100644 src/error.spec.ts
 create mode 100644 src/error.ts

diff --git a/.oxlintrc.json b/.oxlintrc.json
index b14181a..e11a15a 100644
--- a/.oxlintrc.json
+++ b/.oxlintrc.json
@@ -9,9 +9,7 @@
         "typescript/no-non-null-assertion": "off",
         "typescript/no-floating-promises": "error",
         "typescript/no-redundant-type-constituents": "off",
-        "typescript/require-array-sort-compare": "off",
-        "typescript/no-base-to-string": "off",
-        "typescript/restrict-template-expressions": "off"
+        "typescript/require-array-sort-compare": "off"
     },
     "overrides": [
         {
diff --git a/src/error.spec.ts b/src/error.spec.ts
new file mode 100644
index 0000000..d69e5b2
--- /dev/null
+++ b/src/error.spec.ts
@@ -0,0 +1,17 @@
+import {UnexpectedObjectError} from './error';
+
+describe('UnexpectedObjectError', () => {
+    it('works as expected', () => {
+        const item = {it: 'works'};
+        try {
+            throw new UnexpectedObjectError(item as any);
+        } catch (e: any) {
+            expect(e.name).toEqual('UnexpectedObjectError');
+            expect(e.toString()).toEqual('UnexpectedObjectError: DataTransferItem is not a file');
+            expect(e).toBeInstanceOf(Error);
+            expect(e).toBeInstanceOf(UnexpectedObjectError);
+            expect(e.item).toEqual(item);
+            expect(e.stack).toBeDefined();
+        }
+    });
+});
diff --git a/src/error.ts b/src/error.ts
new file mode 100644
index 0000000..ba27fa0
--- /dev/null
+++ b/src/error.ts
@@ -0,0 +1,8 @@
+export class UnexpectedObjectError extends Error {
+    item: DataTransferItem;
+    constructor(item: DataTransferItem) {
+        super('DataTransferItem is not a file');
+        this.item = item;
+        this.name = 'UnexpectedObjectError';
+    }
+}
diff --git a/src/file-selector.spec.ts b/src/file-selector.spec.ts
index 71b3a1b..5c6f586 100644
--- a/src/file-selector.spec.ts
+++ b/src/file-selector.spec.ts
@@ -366,7 +366,7 @@ 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');
+    expect(fromEvent(evt)).rejects.toThrow('DataTransferItem is not a file');
 });
 
 it('should fallback to getAsFile when getAsFileSystemHandle resolves to undefined', async () => {
diff --git a/src/file-selector.ts b/src/file-selector.ts
index 2d1db73..8331e5e 100644
--- a/src/file-selector.ts
+++ b/src/file-selector.ts
@@ -1,3 +1,4 @@
+import {UnexpectedObjectError} from './error';
 import {type FileWithPath, toFileWithPath} from './file';
 
 const FILES_TO_IGNORE = [
@@ -129,7 +130,7 @@ async function fromDataTransferItem(item: DataTransferItem, entry?: FileSystemEn
     if (globalThis.isSecureContext && typeof (item as any).getAsFileSystemHandle === 'function') {
         const h = await (item as any).getAsFileSystemHandle();
         if (h === null) {
-            throw new Error(`${item} is not a File`);
+            throw new UnexpectedObjectError(item);
         }
         // It seems that the handle can be `undefined` (see https://github.com/react-dropzone/file-selector/issues/120),
         // so we check if it isn't; if it is, the code path continues to the next API (`getAsFile`).
@@ -141,7 +142,7 @@ async function fromDataTransferItem(item: DataTransferItem, entry?: FileSystemEn
     }
     const file = item.getAsFile();
     if (!file) {
-        throw new Error(`${item} is not a File`);
+        throw new UnexpectedObjectError(item);
     }
     const fwp = toFileWithPath(file, entry?.fullPath ?? undefined);
     return fwp;