fix(solid-form): fix props reactivity in withForm and withFieldGroupInitialized Repository (#2058)

* fix(solid-form): fix props reactivity in withForm and withFieldGroup

   - Replace object spread with mergeProps() to preserve reactive getters
   - Call render via createComponent() to maintain SolidJS reactive context
   - Add regression tests for withForm and withFieldGroup reactivity

* fix(solid-form): fix props reactivity in withForm and withFieldGroup

   - Replace object spread with mergeProps() to preserve reactive getters
   - Call render via createComponent() to maintain SolidJS reactive context
   - Add regression tests for withForm and withFieldGroup reactivity

   Fixes #2054

* ci: apply automated fixes and generate docs

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

Author: balhyo-younjisang

.changeset/fix-withform-props-reactivity.md

@@ -0,0 +1,7 @@
+---
+'@tanstack/solid-form': patch
+---
+
+Fix props passed to `withForm` and `withFieldGroup` not being reactive.
+
+Object spread (`{ ...props, ...innerProps }`) was eagerly evaluating SolidJS reactive getters, producing a static snapshot that broke signal tracking. Replaced with `mergeProps()` to preserve getter descriptors and `createComponent()` to maintain the correct reactive context.

packages/solid-form/src/createFormHook.tsx

@@ -1,6 +1,7 @@
 import {
   createComponent,
   createContext,
+  mergeProps,
   splitProps,
   useContext,
 } from 'solid-js'
@@ -468,7 +469,11 @@ export function createFormHook<
     UnwrapOrAny<TFormComponents>,
     UnwrapOrAny<TRenderProps>
   >['render'] {
-    return (innerProps) => render({ ...props, ...innerProps })
+    return (innerProps) =>
+      createComponent(
+        render as Component<any>,
+        mergeProps(props ?? {}, innerProps),
+      )
   }
 
   function withFieldGroup<
@@ -553,8 +558,10 @@ export function createFormHook<
         formComponents: opts.formComponents,
       }
       const fieldGroupApi = createFieldGroup(() => fieldGroupProps)
-
-      return render({ ...props, ...innerProps, group: fieldGroupApi as any })
+      return createComponent(
+        render as Component<any>,
+        mergeProps(props ?? {}, innerProps, { group: fieldGroupApi as any }),
+      )
     }
   }
 

packages/solid-form/tests/createFormHook.test.tsx

@@ -1,7 +1,8 @@
-import { describe, expect, it } from 'vitest'
+import { describe, expect, it, vi } from 'vitest'
 import { render } from '@solidjs/testing-library'
 import { formOptions } from '@tanstack/form-core'
 import userEvent from '@testing-library/user-event'
+import { createEffect, createSignal } from 'solid-js'
 import { createFormHook, createFormHookContexts, useStore } from '../src'
 
 const user = userEvent.setup()
@@ -535,6 +536,129 @@ describe('createFormHook', () => {
     render(() => <Parent />)
   })
 
+  it('should keep props reactive in JSX when passed to withForm component', async () => {
+    const formOpts = formOptions({ defaultValues: { name: '' } })
+
+    const StatusForm = withForm({
+      ...formOpts,
+      props: {
+        status: 'idle' as 'idle' | 'loading',
+        count: 0,
+      },
+      render: (props) => (
+        <div>
+          <span data-testid="status">{props.status}</span>
+          <span data-testid="count">{props.count}</span>
+        </div>
+      ),
+    })
+
+    const Parent = () => {
+      const form = useAppForm(() => formOpts)
+      const [status, setStatus] = createSignal<'idle' | 'loading'>('idle')
+      const [count, setCount] = createSignal(0)
+      return (
+        <div>
+          <StatusForm form={form} status={status()} count={count()} />
+          <button data-testid="btn-status" onClick={() => setStatus('loading')}>
+            change
+          </button>
+          <button
+            data-testid="btn-count"
+            onClick={() => setCount((c) => c + 1)}
+          >
+            inc
+          </button>
+        </div>
+      )
+    }
+
+    const { getByTestId } = render(() => <Parent />)
+
+    expect(getByTestId('status')).toHaveTextContent('idle')
+    expect(getByTestId('count')).toHaveTextContent('0')
+
+    await user.click(getByTestId('btn-status'))
+    expect(getByTestId('status')).toHaveTextContent('loading')
+
+    await user.click(getByTestId('btn-count'))
+    expect(getByTestId('count')).toHaveTextContent('1')
+  })
+
+  it('should re-run createEffect when reactive props change in withForm render', async () => {
+    const formOpts = formOptions({ defaultValues: { name: '' } })
+    const spy = vi.fn()
+
+    const StatusForm = withForm({
+      ...formOpts,
+      props: { status: 'idle' as 'idle' | 'loading' },
+      render: (props) => {
+        createEffect(() => {
+          spy(props.status)
+        })
+        return <div data-testid="status">{props.status}</div>
+      },
+    })
+
+    const Parent = () => {
+      const form = useAppForm(() => formOpts)
+      const [status, setStatus] = createSignal<'idle' | 'loading'>('idle')
+      return (
+        <div>
+          <StatusForm form={form} status={status()} />
+          <button data-testid="btn" onClick={() => setStatus('loading')}>
+            change
+          </button>
+        </div>
+      )
+    }
+
+    const { getByTestId } = render(() => <Parent />)
+
+    expect(spy).toHaveBeenCalledTimes(1)
+    expect(spy).toHaveBeenLastCalledWith('idle')
+
+    await user.click(getByTestId('btn'))
+    expect(spy).toHaveBeenCalledTimes(2)
+    expect(spy).toHaveBeenLastCalledWith('loading')
+  })
+
+  it('should keep props reactive in withFieldGroup component', async () => {
+    const formOpts = formOptions({
+      defaultValues: { person: { firstName: 'John' } },
+    })
+
+    const PersonGroup = withFieldGroup({
+      defaultValues: formOpts.defaultValues.person,
+      props: { label: 'default' },
+      render: (props) => (
+        <div>
+          <span data-testid="label">{props.label}</span>
+        </div>
+      ),
+    })
+
+    const Parent = () => {
+      const form = useAppForm(() => formOpts)
+      const [label, setLabel] = createSignal('initial')
+      return (
+        <div>
+          <PersonGroup form={form} fields="person" label={label()} />
+          <button data-testid="btn" onClick={() => setLabel('updated')}>
+            change
+          </button>
+        </div>
+      )
+    }
+
+    const { getByTestId } = render(() => <Parent />)
+
+    expect(getByTestId('label')).toHaveTextContent('initial')
+
+    await user.click(getByTestId('btn'))
+    expect(getByTestId('label')).toHaveTextContent('updated')
+  })
+
   it('should accept formId and return it', async () => {
     function Submit() {
       const form = useFormContext()