From 81c50db9136820c7981302cc2fa398cf781303c2 Mon Sep 17 00:00:00 2001
From: MarkXian <mark-xian@foxmail.com>
Date: Tue, 14 Jul 2026 20:41:41 +0800
Subject: [PATCH 1/2] fix(form-core): create complete field meta on
 setFieldValue for uninitialized fields

When `setFieldValue` targets a field that has not been mounted yet (e.g. a
conditionally rendered field pre-populated before render), the meta updater
spread an `undefined` previous meta, producing a partial object missing
required fields such as `isValidating`, `isBlurred` and `errorSourceMap`.

Default the previous meta to `defaultFieldMeta` so the newly created meta is
structurally complete and consistent with a normally mounted field, matching
the pattern already used by other `setFieldMeta` call sites.

Closes #1078
---
 packages/form-core/src/FormApi.ts        |  5 ++---
 packages/form-core/tests/FormApi.spec.ts | 27 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/packages/form-core/src/FormApi.ts b/packages/form-core/src/FormApi.ts
index d710cd105..cc5bed9be 100644
--- a/packages/form-core/src/FormApi.ts
+++ b/packages/form-core/src/FormApi.ts
@@ -2659,13 +2659,12 @@ export class FormApi<
 
     batch(() => {
       if (!dontUpdateMeta) {
-        this.setFieldMeta(field, (prev) => ({
+        this.setFieldMeta(field, (prev = defaultFieldMeta) => ({
           ...prev,
           isTouched: true,
           isDirty: true,
           errorMap: {
-            // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
-            ...prev?.errorMap,
+            ...prev.errorMap,
             onMount: undefined,
           },
         }))
diff --git a/packages/form-core/tests/FormApi.spec.ts b/packages/form-core/tests/FormApi.spec.ts
index 024b319f0..b370fb31b 100644
--- a/packages/form-core/tests/FormApi.spec.ts
+++ b/packages/form-core/tests/FormApi.spec.ts
@@ -83,6 +83,33 @@ describe('form api', () => {
     })
   })
 
+  it('should create complete meta when setFieldValue targets an uninitialized field', () => {
+    const form = new FormApi({
+      defaultValues: {
+        availableFor: 'longStay',
+      } as { availableFor: string; fees?: number },
+    })
+    form.mount()
+
+    // `fees` is rendered conditionally and has not been mounted yet, so its
+    // meta is created for the first time by this call.
+    form.setFieldValue('fees', 1)
+
+    const meta = form.getFieldMeta('fees')
+
+    // Every documented meta field must be present (not `undefined`), matching
+    // the meta of a field that has been mounted normally.
+    expect(meta).toMatchObject({
+      isValidating: false,
+      isBlurred: false,
+      errors: [],
+      errorSourceMap: {},
+    })
+    expect(meta?.isValidating).not.toBeUndefined()
+    expect(meta?.isBlurred).not.toBeUndefined()
+    expect(meta?.errorSourceMap).not.toBeUndefined()
+  })
+
   it('should reset with provided custom default values', () => {
     const defaultValues = {
       name: 'test',

From 51d41039231a282ae8ecd9620052fc359695c628 Mon Sep 17 00:00:00 2001
From: MarkXian <mark-xian@foxmail.com>
Date: Wed, 15 Jul 2026 15:01:50 +0800
Subject: [PATCH 2/2] test(form-core): assert touched and dirty state for meta
 created by setFieldValue

---
 packages/form-core/tests/FormApi.spec.ts | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/packages/form-core/tests/FormApi.spec.ts b/packages/form-core/tests/FormApi.spec.ts
index b370fb31b..802801e7f 100644
--- a/packages/form-core/tests/FormApi.spec.ts
+++ b/packages/form-core/tests/FormApi.spec.ts
@@ -102,6 +102,9 @@ describe('form api', () => {
     expect(meta).toMatchObject({
       isValidating: false,
       isBlurred: false,
+      // `setFieldValue` marks the newly created meta as touched and dirty.
+      isTouched: true,
+      isDirty: true,
       errors: [],
       errorSourceMap: {},
     })