validator doesnt parse nested objects in formdata

[darklight9811]

What version of Hono are you using?

4.6.12

What runtime/platform is your app running on? (with version if possible)

bun 1.1.37

What steps can reproduce the bug?

• Use this to parse the object into formdata on the frontend:

objectToFormData

This is compliant with zod-form-data

// biome-ignore lint/suspicious/noExplicitAny: <explanation>
export function appendFormData(data: any, root: string, formData: FormData) {
	if (data instanceof File) return formData.append(root, data);
	if (Array.isArray(data)) {
		for (let i = 0; i < data.length; i++) {
			appendFormData(data[i], `${root}[${i}]`, formData);
		}

		return;
	}
	if (data instanceof Date) {
		return formData.append(root, data.toISOString());
	}
	if (typeof data === "object" && data) {
		for (const key in data) {
			// biome-ignore lint/suspicious/noPrototypeBuiltins: <explanation>
			if (data.hasOwnProperty(key)) {
				if (root === "") appendFormData(data[key], key, formData);
				else appendFormData(data[key], `${root}.${key}`, formData);
			}
		}

		return;
	}
	if (data !== null && typeof data !== "undefined")
		return formData.append(root, data);
}

export function objectToFormData(obj: unknown, rootName = "") {
	const formData = new FormData();

	appendFormData(obj, rootName, formData);

	return formData;
}

• Send the data to the backend
• Parse it with validator:

app.post(
  '/posts',
  validator('form', (value, c) => {
    console.log(value);
  //...

What is the expected behavior?

Have deep nested objects sent like this:

FormData {
   name: "Test",
   img: File (170.37 KB) {
     name: "Purple.png",
     type: "image/png"
   },
   "address.id": "dXJuOm1ieHBvaTpkNjUyMjUxOC04NDMzLTRlNzQtYjM5MS1iOGRkZDZlZDg4ZTA",
   "address.label": "Testaccio market, 00153 Rome, Italy",
   "address.coords[0]": 12.47373157,
   "address.coords[1]": 41.87758156,
}

To be parsed like this:

{
   name: "Test",
   img: File (170.37 KB) {
     name: "Purple.png",
     type: "image/png"
   },
   "address": {
      "id": "dXJuOm1ieHBvaTpkNjUyMjUxOC04NDMzLTRlNzQtYjM5MS1iOGRkZDZlZDg4ZTA",
      "label": "Testaccio market, 00153 Rome, Italy",
      "coords": [12.47373157, 41.87758156],
    }
}

What do you see instead?

{
   name: "Test",
   img: File (170.37 KB) {
     name: "Purple.png",
     type: "image/png"
   },
   "address.id": "dXJuOm1ieHBvaTpkNjUyMjUxOC04NDMzLTRlNzQtYjM5MS1iOGRkZDZlZDg4ZTA",
   "address.label": "Testaccio market, 00153 Rome, Italy",
   "address.coords[0]": "12.47373157",
   "address.coords[1]": "41.87758156",
}

Additional information

Also noticed the number got cast into string

[yusukebe]

Hi @darklight9811

Do you think this is a bug or a feature request?

[darklight9811]

Hi @darklight9811

Do you think this is a bug or a feature request?

I think it fits both, since it's a limitation

[yusukebe]

This is not a bug and is an expected behavior. We have not implemented this feature and I don't know we should do it. So, I'll tag this as an enhancement.