fix(form-core): validate fields without components when setFieldValue…

packages/form-core/src/FormApi.ts

@@ -1589,7 +1589,13 @@ export class FormApi<
   ) => {
     // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
     const fieldInstance = this.fieldInfo[field]?.instance
-    if (!fieldInstance) return []
+
+    if (!fieldInstance) {
+      // If there's no field instance, we still need to run form-level validation
+      // to ensure fields without components can still be validated
+      this.validate(cause)
+      return []
+    }
 
     // If the field is not touched (same logic as in validateAllFields)
     if (!fieldInstance.state.meta.isTouched) {

packages/form-core/tests/setFieldValue-validation.spec.ts

@@ -0,0 +1,86 @@
+import { describe, expect, it } from 'vitest'
+import { FormApi } from '../src/FormApi'
+
+describe('setFieldValue validation for fields without components', () => {
+  it('should validate field when setFieldValue is called even without field component', () => {
+    const form = new FormApi({
+      defaultValues: {
+        name: '',
+      },
+      validators: {
+        onChange: ({ value }) => {
+          if (!value.name) {
+            return {
+              fields: {
+                name: 'Name is required',
+              },
+            }
+          }
+          return undefined
+        },
+      },
+    })
+
+    form.mount()
+
+    // Initially, form should be valid (no validation errors yet)
+    expect(form.state.isValid).toBe(true)
+    expect(form.state.errors).toEqual([])
+
+    // Set field value to empty string (should trigger validation and show error)
+    form.setFieldValue('name', '')
+
+    // Form should now be invalid due to validation error
+    expect(form.state.isValid).toBe(false)
+    expect(form.state.fieldMeta.name?.errors).toEqual(['Name is required'])
+
+    // Set field value to valid value (should clear validation error)
+    form.setFieldValue('name', 'John')
+
+    // Form should now be valid again
+    expect(form.state.isValid).toBe(true)
+    expect(form.state.fieldMeta.name?.errors).toEqual([])
+  })
+
+  it('should validate field with form-level async validator', async () => {
+    const form = new FormApi({
+      defaultValues: {
+        email: '',
+      },
+      validators: {
+        onChangeAsync: async ({ value }) => {
+          if (!value.email) {
+            return {
+              fields: {
+                email: 'Email is required',
+              },
+            }
+          }
+          return undefined
+        },
+      },
+    })
+
+    form.mount()
+
+    // Set field value to empty string (should trigger async validation)
+    form.setFieldValue('email', '')
+
+    // Wait for async validation to complete
+    await new Promise((resolve) => setTimeout(resolve, 100))
+
+    // Form should now be invalid due to validation error
+    expect(form.state.isValid).toBe(false)
+    expect(form.state.fieldMeta.email?.errors).toEqual(['Email is required'])
+
+    // Set field value to valid value (should clear validation error)
+    form.setFieldValue('email', 'john@example.com')
+
+    // Wait for async validation to complete
+    await new Promise((resolve) => setTimeout(resolve, 100))
+
+    // Form should now be valid again
+    expect(form.state.isValid).toBe(true)
+    expect(form.state.fieldMeta.email?.errors).toEqual([])
+  })
+})