`field.errors` incorrectly nested when calling `form.validate('change')` manually

[swushi]

Describe the bug

When calling form.validate('change') manually (e.g., after mounting conditional fields), field.errors contains a different structure than when validation runs through normal onChange events.

• Normal onChange validation: field.errors = [{ "code": "too_small", ...restOfZodError }]
• Manual form.validate('change') call: field.errors = [[{ "code": "too_small", ...restOfZodError }]]

The errors are wrapped in an extra array when using the manual validate call.

Your minimal, reproducible example

https://stackblitz.com/edit/tanstack-form-wawszjkd?file=src%2Findex.tsx

Steps to reproduce

1. Click checkbox to mount conditional fields
2. Expect error to show up, but error is wrapped in array (see logs for more info)

Expected behavior

For errors from form.validate(...) to have the same output as an organic change event. I'd expect to see an error immediately after clicking the checkbox.

How often does this bug happen?

Every time

Screenshots or Videos

No response

Platform

• Stackblitz
• Mac

TanStack Form adapter

react-form

TanStack Form version

1.27.7

TypeScript version

No response

Additional context

Chatting through this in Discord as well: convo

It also seems like if mount, unmount, then mount again, form.validate(...) produces the correct result.

[Bernardo-ive]

I'm having the exactly same issue, noticed that filling a value it then the errors structure is as expected. maybe cos i'm using onDynamic validation.

const form = useAppForm({
		...briefFormOptions,
		defaultValues: {
			...briefFormOptions.defaultValues,
			contactName: contactName,
		},
		validators: {
			onDynamic: briefFormSchemaZod,
		},
		onSubmit: async ({ value }) => {
			alert(JSON.stringify(value))
		},
		validationLogic: revalidateLogic({
			mode: 'submit',
			modeAfterSubmission: 'change',
		}),
	})

[arekrgw]

I feel I have the same issue or at least something similar

Here is a repro, just switch between tabs and see the errors json structure

https://codesandbox.io/p/sandbox/shpy79

[Kyujenius]

I ran into this exact same issue. Just submitted a PR with a fix that addresses the root cause in FormApi.validateSync(). 😄

The problem was that the flat(1) operation only applied when fieldInstance existed, causing unmounted fields to retain nested error arrays.

PR: #2003