fix(form): a split form keeps BOTH panels' values (#2153) (#3012)

SplitForm rendered one SchemaRenderer — one react-hook-form instance and one
<form> element — PER section, and its two groups of sections live in separate
ResizablePanel children. So each panel owned isolated form state: submitting
from one panel's action bar sent only that section's fields and silently
dropped everything typed on the other side of the divider. Filling both panels
and clicking Create persisted { subject } alone.

The same isolation killed cross-panel field rules: a visibleWhen in the right
panel referencing a left-panel field never saw that field in its rule record,
so the predicate faulted and failed OPEN — the field the author meant to hide
was always shown.

Both panels are now ONE form, the same way #2959 fixed the tabbed hosts. A
single <form> cannot straddle two panels from INSIDE them, so the panel group
became a layout the form renderer owns: a new FormSchema.fieldPanes
(+ fieldPanesOrientation, fieldPanesResizable) mirroring fieldTabs, where the
<form> wraps the whole ResizablePanelGroup and each pane holds only fields.
Sections inside a pane render behind the inline section-divider header, each at
its own declared column density within the form's shared grid.

Also fixed by moving the panels into the renderer: splitResizable: false now
actually pins the divider (it only hid the grip before, leaving the separator
draggable — nothing passed the panel library's `disabled`).

Each pane is its own @container, so a multi-column section collapses to fewer
columns as its panel is dragged narrower instead of overflowing.

Verified in a real browser (zero-backend console harness): one <form> holding
both panes, typing 'urgent' in the left pane reveals the right pane's
conditional field, and the submit payload carries every field from both sides.

Co-authored-by: Jack Zhuang <277994282+os-zhuang@users.noreply.github.com>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

Author: os-zhuang

.changeset/split-form-keeps-both-panels.md

@@ -0,0 +1,35 @@
+---
+"@object-ui/types": patch
+"@object-ui/components": patch
+"@object-ui/plugin-form": patch
+---
+
+fix(form): a split create/edit form no longer loses the panel you are not submitting from (#2153)
+
+`SplitForm` rendered one `SchemaRenderer` — one react-hook-form instance and one
+`<form>` element — **per section**, and its two groups of sections live in
+separate resizable panels. So each panel owned isolated form state: submitting
+from one panel's action bar sent only that section's fields and silently dropped
+everything the user had typed on the other side of the divider. Filling both
+panels and clicking Create persisted `{ subject }` alone.
+
+The same isolation killed cross-panel field rules: a `visibleWhen` in the right
+panel referencing a left-panel field never saw that field in its record, so the
+predicate faulted and failed **open** — the field the author meant to hide was
+always shown.
+
+Both panels are now ONE form. The panel group became a layout the form renderer
+owns, via a new `FormSchema.fieldPanes` (+ `fieldPanesOrientation`,
+`fieldPanesResizable`) that mirrors `fieldTabs` (#2959): the `<form>` wraps the
+whole `ResizablePanelGroup` and each pane holds only fields, which is what lets a
+single react-hook-form instance span the divider. Sections inside a pane render
+behind the inline `section-divider` header, each at its own declared column
+density within the form's shared grid.
+
+One more fix falls out of moving the panels into the renderer: `splitResizable:
+false` now actually pins the divider. It previously only hid the grip — the
+separator stayed draggable, because nothing passed the panel library's
+`disabled`.
+
+Each pane is its own `@container`, so a multi-column section collapses to fewer
+columns as its panel is dragged narrower instead of overflowing.

content/docs/plugins/plugin-form.mdx

@@ -91,6 +91,36 @@ inactive tab unmount along with its values).
 
 `ModalForm` (`contentLayout: 'tabbed'`) and `TabbedForm` build on this.
 
+### Split field layout (`fieldPanes`)
+
+Side-by-side panels follow the same rule: the `<form>` wraps the whole panel
+group and each pane holds only fields, so one react-hook-form instance spans the
+divider.
+
+```plaintext
+{
+  type: 'form',
+  fields: [/* every pane's fields, in one flat list */],
+  fieldPanes: [
+    { key: 'primary', fields: ['subject'], defaultSize: 50 },
+    { key: 'secondary', fields: ['status', 'priority'], defaultSize: 50, minSize: 20 },
+  ],
+  fieldPanesOrientation?: 'horizontal',   // 'horizontal' | 'vertical'
+  fieldPanesResizable?: true,             // false pins the divider
+}
+```
+
+- A submit from anywhere carries every pane's values, and a field rule in one
+  pane can read a field in another — neither works with a form per panel.
+- `defaultSize` / `minSize` are percentages of the group.
+- Each pane is its own `@container`, so a multi-column group collapses as the
+  divider is dragged narrower.
+- Fields no pane claims render above the panel group rather than disappearing.
+- Needs at least two panes; ignored when the form uses `children` or `fieldTabs`.
+
+`SplitForm` builds on this: section 1 becomes the primary pane, the rest stack in
+the secondary one behind inline section headers.
+
 ## Usage
 
 ### Auto-registration (Side-effect Import)

packages/components/src/renderers/form/__tests__/form-field-panes.test.tsx

@@ -0,0 +1,217 @@
+/**
+ * ObjectUI
+ * Copyright (c) 2024-present ObjectStack Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * #2153: `FormSchema.fieldPanes` — a split field layout inside ONE form.
+ *
+ * The sibling of `fieldTabs` (#2959), for side-by-side panels. A `<form>` cannot
+ * live inside each panel and still be one form, so the renderer puts the `<form>`
+ * around the whole panel group and the panels hold only fields.
+ *
+ * The contract these pin:
+ *  - one `<form>` / react-hook-form instance across every pane, so a submit
+ *    carries all of them and a field rule can read across the divider;
+ *  - a field no pane claims is still rendered (never silently dropped);
+ *  - the pane schema keys never reach the `<form>` DOM element;
+ *  - `fieldPanesResizable: false` actually pins the divider.
+ *
+ * Pane SIZES cannot be asserted here: react-resizable-panels resolves them
+ * against the measured group width, which is 0 under happy-dom, so every panel
+ * comes out an even `flex-grow: 50`. They are verified in a real browser.
+ */
+
+import { describe, it, expect, beforeAll, beforeEach, afterEach, vi } from 'vitest';
+import { render, screen, fireEvent, waitFor, cleanup } from '@testing-library/react';
+import { ComponentRegistry } from '@object-ui/core';
+
+beforeAll(async () => {
+  await import('../../../renderers');
+}, 30000);
+
+beforeEach(() => {
+  if (!(Element.prototype as any).scrollIntoView) {
+    (Element.prototype as any).scrollIntoView = () => {};
+  }
+});
+
+afterEach(() => {
+  cleanup();
+  vi.restoreAllMocks();
+});
+
+const FIELDS = [
+  { name: 'subject', label: 'Subject', type: 'input' },
+  { name: 'status', label: 'Status', type: 'input' },
+  { name: 'priority', label: 'Priority', type: 'input' },
+];
+
+const PANES = [
+  { key: 'primary', fields: ['subject'], defaultSize: 40 },
+  { key: 'secondary', fields: ['status', 'priority'], defaultSize: 60 },
+];
+
+function renderSplitForm(overrides: Record<string, unknown> = {}) {
+  const onSubmit = vi.fn();
+  const Form = ComponentRegistry.get('form')!;
+  const utils = render(
+    <Form
+      schema={{
+        type: 'form',
+        mode: 'create',
+        showSubmit: true,
+        showCancel: false,
+        submitLabel: 'Create',
+        fields: FIELDS,
+        fieldPanes: PANES,
+        onSubmit,
+        ...overrides,
+      }}
+    />,
+  );
+  return { ...utils, onSubmit };
+}
+
+const fill = (name: string, value: string) => {
+  const input = document.body.querySelector<HTMLInputElement>(`[data-field="${name}"] input`);
+  if (!input) throw new Error(`field not rendered: ${name}`);
+  fireEvent.change(input, { target: { value } });
+};
+
+const pane = (key: string) => document.body.querySelector(`[data-testid="form-pane:${key}"]`);
+
+describe('FormSchema.fieldPanes — one form across the split (#2153)', () => {
+  it('renders one <form> and lays each pane out in its own panel', () => {
+    const { container } = renderSplitForm();
+
+    expect(container.querySelectorAll('form')).toHaveLength(1);
+    expect(pane('primary')?.querySelector('[data-field="subject"]')).toBeTruthy();
+    expect(pane('secondary')?.querySelector('[data-field="status"]')).toBeTruthy();
+    expect(pane('secondary')?.querySelector('[data-field="priority"]')).toBeTruthy();
+    // Both panes are inside the single form, not the other way round (which is
+    // the arrangement that cannot work: a <form> per panel).
+    const form = container.querySelector('form')!;
+    expect(form.querySelector('[data-testid="form-pane:primary"]')).toBeTruthy();
+    expect(form.querySelector('[data-testid="form-pane:secondary"]')).toBeTruthy();
+  });
+
+  it('submits every pane’s values', async () => {
+    const { onSubmit } = renderSplitForm();
+
+    fill('subject', 'Printer on fire');
+    fill('status', 'open');
+    fill('priority', 'high');
+
+    fireEvent.click(screen.getByRole('button', { name: 'Create' }));
+
+    await waitFor(() => expect(onSubmit).toHaveBeenCalledTimes(1));
+    expect(onSubmit.mock.calls[0][0]).toMatchObject({
+      subject: 'Printer on fire',
+      status: 'open',
+      priority: 'high',
+    });
+  });
+
+  it('evaluates a field rule across the divider', async () => {
+    renderSplitForm({
+      fields: [
+        ...FIELDS,
+        {
+          name: 'escalation',
+          label: 'Escalation',
+          type: 'input',
+          // Watches a field in the OTHER pane — only one shared react-hook-form
+          // instance can see it. With a form per panel the predicate faulted on
+          // the missing key and failed open, so the field was always visible.
+          visibleWhen: "record.subject == 'urgent'",
+        },
+      ],
+      fieldPanes: [
+        { key: 'primary', fields: ['subject'] },
+        { key: 'secondary', fields: ['status', 'escalation'] },
+      ],
+    });
+
+    expect(document.body.querySelector('[data-field="escalation"]')).toBeNull();
+
+    fill('subject', 'urgent');
+
+    await waitFor(() =>
+      expect(pane('secondary')?.querySelector('[data-field="escalation"]')).toBeTruthy(),
+    );
+  });
+
+  it('keeps the pane schema keys off the <form> DOM element', () => {
+    // Callers / the SDUI dispatch spread the whole form node at the top level as
+    // well, so an unconsumed FormSchema key leaks onto the DOM and React logs
+    // "does not recognize the `fieldPanes` prop on a DOM element".
+    const Form = ComponentRegistry.get('form')!;
+    const { container } = render(
+      <Form
+        schema={{ type: 'form', fields: FIELDS, fieldPanes: PANES }}
+        // The top-level spread that reproduces the leak.
+        fields={FIELDS}
+        fieldPanes={PANES}
+        fieldPanesOrientation="vertical"
+        fieldPanesResizable={false}
+      />,
+    );
+    const form = container.querySelector('form')!;
+    for (const attr of ['fieldpanes', 'fieldpanesorientation', 'fieldpanesresizable']) {
+      expect(form.hasAttribute(attr)).toBe(false);
+    }
+  });
+
+  it('renders fields no pane claims instead of dropping them', () => {
+    const { container } = renderSplitForm({
+      fieldPanes: [
+        { key: 'primary', fields: ['subject'] },
+        { key: 'secondary', fields: ['status'] },
+      ],
+    });
+
+    // `priority` belongs to no pane — still in the DOM, outside the panels.
+    const priority = container.querySelector('[data-field="priority"]')!;
+    expect(priority).toBeTruthy();
+    expect(priority.closest('[data-panel]')).toBeNull();
+  });
+
+  it('falls back to a plain field list for a single pane', () => {
+    const { container } = renderSplitForm({
+      fieldPanes: [{ key: 'only', fields: ['subject'] }],
+    });
+
+    expect(container.querySelector('[data-panel]')).toBeNull();
+    expect(pane('only')).toBeNull();
+    // …and every field still renders, not just the one the lone pane claimed.
+    expect(container.querySelector('[data-field="priority"]')).toBeTruthy();
+  });
+
+  it('lets a tabbed layout win when a caller declares both', () => {
+    renderSplitForm({
+      fieldTabs: [
+        { key: 'basics', label: 'Basics', fields: ['subject'] },
+        { key: 'triage', label: 'Triage', fields: ['status', 'priority'] },
+      ],
+    });
+
+    expect(screen.getAllByRole('tab')).toHaveLength(2);
+    expect(pane('primary')).toBeNull();
+  });
+
+  it('pins the divider when fieldPanesResizable is false', () => {
+    const { container } = renderSplitForm({ fieldPanesResizable: false });
+    const separator = container.querySelector('[role="separator"]')!;
+    expect(separator.getAttribute('aria-disabled')).toBe('true');
+  });
+
+  it('leaves the divider draggable by default', () => {
+    const { container } = renderSplitForm();
+    const separator = container.querySelector('[role="separator"]')!;
+    expect(separator.getAttribute('aria-disabled')).not.toBe('true');
+  });
+});