fix(form): 统一 extendState 合并逻辑

packages/form/src/Form.vue

@@ -40,7 +40,7 @@ import { setValueByKeyPath } from '@tmagic/utils';
 
 import Container from './containers/Container.vue';
 import { getConfig } from './utils/config';
-import { initValue } from './utils/form';
+import { applyExtendState, initValue } from './utils/form';
 import type {
   ChangeRecord,
   ContainerChangeEventData,
@@ -222,11 +222,10 @@ const formState: FormState = reactive<FormState>({
  * 这里不再重复同步；因此 `props.initValues` 这类高频变化也不会再触发
  * `extendState` 重跑（旧版的性能问题修复点）。
  *
- * 实现细节：
- * - data 描述符：通过 `formState[key] = value` 走 reactive proxy 的 set，
- *   触发依赖通知；与旧版「逐项赋值」语义完全等价。
- * - accessor 描述符（`{ get stage() {...} }`）按原样写入 formState，调用方
- *   可以自行控制读时求值；强制 `configurable: true` 以便下一次重跑可再 define。
+ * 实现细节：合并逻辑统一收口在 `applyExtendState`（utils/form）——
+ * data 描述符走 reactive proxy 的 set 触发依赖通知（与旧版「逐项赋值」语义等价），
+ * accessor 描述符按原样 defineProperty 支持读时求值；
+ * props 派生的只读 getter 字段（keyProp 等）以普通字段形式返回时会被跳过并告警。
  */
 watchEffect(async (onCleanup) => {
   const { extendState } = props;
@@ -246,14 +245,7 @@ watchEffect(async (onCleanup) => {
   }
   if (stale) return;
 
-  for (const [key, descriptor] of Object.entries(Object.getOwnPropertyDescriptors(state))) {
-    if ('value' in descriptor) {
-      (formState as any)[key] = (state as any)[key];
-    } else {
-      descriptor.configurable = true;
-      Object.defineProperty(formState, key, descriptor);
-    }
-  }
+  applyExtendState(formState, state);
 });
 
 provide('mForm', formState);

packages/form/src/submitForm.ts

@@ -18,6 +18,7 @@
 
 import { type AppContext, type Component, createApp, defineComponent, h, nextTick, type Ref, ref, watch } from 'vue';
 
+import { applyExtendState } from './utils/form';
 import Form from './Form.vue';
 import type { ChangeRecord, FormConfig, FormState } from './schema';
 
@@ -192,17 +193,10 @@ const mountFormInstance = <T>(options: MountFormInstanceOptions<T>): Promise<T>
                     console.error('[MForm] extendState failed:', e);
                     return;
                   }
-                  const apply = (state: Record<string, any> | null | undefined) => {
-                    if (!state) return;
-                    for (const [key, descriptor] of Object.entries(Object.getOwnPropertyDescriptors(state))) {
-                      if ('value' in descriptor) {
-                        (form.formState as any)[key] = (state as any)[key];
-                      } else {
-                        descriptor.configurable = true;
-                        Object.defineProperty(form.formState, key, descriptor);
-                      }
-                    }
-                  };
+                  // 合并逻辑收口在 applyExtendState：props 派生的只读 getter 字段
+                  // （keyProp 等）以普通字段形式返回时会被跳过并告警，避免 proxy set 抛错
+                  const apply = (state: Record<string, any> | null | undefined) =>
+                    applyExtendState(form.formState, state);
                   if (result && typeof result.then === 'function') {
                     result.then(apply, (e: any) => console.error('[MForm] extendState failed:', e));
                   } else {

packages/form/src/utils/form.ts

@@ -441,6 +441,43 @@ export const sortChange = (data: any[], { prop, order }: SortProp) => {
   }
 };
 
+/**
+ * 将 extendState 返回的扩展字段合并进 formState。
+ *
+ * - data 描述符（普通字段）通过 `formState[key] = value` 写入，走 reactive proxy 的 set，
+ *   触发依赖通知；
+ * - accessor 描述符（`{ get stage() { return ... } }`）按原样 defineProperty，调用方
+ *   可控制读时求值；强制 `configurable: true` 以便下一次合并可再 define。
+ *
+ * 注意：formState 上由 props 派生的字段（keyProp / popperClass / config / initValues /
+ * isCompare / lastValues / parentValues）是只读 getter（无 setter），extendState 若以
+ * 普通字段形式返回同名 key，直接赋值会让 proxy 的 set trap 失败并抛出
+ * `TypeError: 'set' on proxy: trap returned falsish`，这里统一跳过并告警；
+ * 如确需覆盖，可在 extendState 中以 get 访问器形式返回。
+ */
+export const applyExtendState = (formState: FormState, state: Record<string, any> | null | undefined): void => {
+  if (!state) return;
+
+  for (const [key, descriptor] of Object.entries(Object.getOwnPropertyDescriptors(state))) {
+    if (!('value' in descriptor)) {
+      descriptor.configurable = true;
+      Object.defineProperty(formState, key, descriptor);
+      continue;
+    }
+
+    const targetDescriptor = Object.getOwnPropertyDescriptor(formState, key);
+    if (targetDescriptor && !('value' in targetDescriptor) && typeof targetDescriptor.set !== 'function') {
+      console.warn(
+        `[MForm] extendState: "${key}" is a read-only field derived from props and cannot be assigned a plain value. ` +
+          'Return it as a getter accessor if you really need to override it.',
+      );
+      continue;
+    }
+
+    (formState as any)[key] = (state as any)[key];
+  }
+};
+
 export const createObjectProp = (prop: string, key: string, name?: string | number) => {
   if (prop === '') {
     return key;

packages/form/tests/unit/Form.extra.spec.ts

@@ -173,6 +173,48 @@ describe('Form.vue —— extendState', () => {
     expect(v2).toMatch(/^stage-/);
   });
 
+  test('extendState 以普通字段返回 props 派生的只读字段时跳过并告警，不抛错', async () => {
+    const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+    const wrapper = mountForm({
+      keyProp: 'id',
+      extendState: () => ({ keyProp: 'custom', config: [], extra: 'ok' }),
+    });
+
+    await nextTick();
+    await nextTick();
+    await nextTick();
+
+    // 只读派生字段保持 props 值，未被覆盖
+    expect((wrapper.vm.formState as any).keyProp).toBe('id');
+    expect(Array.isArray((wrapper.vm.formState as any).config)).toBe(true);
+    // 其他字段正常合并
+    expect((wrapper.vm.formState as any).extra).toBe('ok');
+    expect(warnSpy).toHaveBeenCalled();
+    expect(wrapper.find('.m-form').exists()).toBe(true);
+
+    warnSpy.mockRestore();
+  });
+
+  test('extendState 以 get 访问器返回只读字段同名 key 时允许显式覆盖', async () => {
+    const wrapper = mountForm({
+      keyProp: 'id',
+      extendState: () =>
+        Object.defineProperties(
+          {},
+          {
+            keyProp: { enumerable: true, get: () => 'custom-key' },
+          },
+        ),
+    });
+
+    await nextTick();
+    await nextTick();
+    await nextTick();
+
+    expect((wrapper.vm.formState as any).keyProp).toBe('custom-key');
+  });
+
   test('extendState 同步段读到的响应式数据变化时会重跑', async () => {
     const username = ref('alice');
     const calls: string[] = [];

packages/form/tests/unit/submitForm.spec.ts

@@ -79,6 +79,22 @@ describe('submitForm', () => {
     expect(extendState).toHaveBeenCalled();
   });
 
+  test('extendState 返回 keyProp 等只读派生字段时不抛错且正常 resolve', async () => {
+    const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+    const values = await submitForm({
+      config: [{ type: 'text', name: 'text', text: 'text' }],
+      initValues: { text: 'foo' },
+      extendState: () => ({ keyProp: 'custom', extra: 'value' }),
+      appContext,
+    });
+
+    expect(values).toEqual({ text: 'foo' });
+    expect(warnSpy).toHaveBeenCalled();
+
+    warnSpy.mockRestore();
+  });
+
   test('在嵌套 items 配置下也能正确 resolve', async () => {
     const values = await submitForm({
       config: [