fix: do second pass of fixes

Author: LeCarbonator

.changeset/tasty-humans-joke.md

@@ -2,4 +2,4 @@
 '@tanstack/form-core': patch
 ---
 
-Refactor: Migrate Form Groups's storage and accessing
+Refactor: Store Form Groups on trie nodes instead of the form instance

packages/form-core/src/FieldApi/fieldTree.lib.ts

@@ -265,9 +265,22 @@ function notifyFieldSubtreeListeners(
 function prepareFormGroupsForFieldReplacement(
   fields: ReadonlyArray<AnyInternalFieldApi>,
 ): () => void {
+  const fieldsToReplace = new Set(fields)
   const formGroups = fields.flatMap((field) =>
     field._formGroup ? [{ group: field._formGroup, name: field.name }] : [],
   )
+  const affectedFormGroups = new Set(formGroups.map(({ group }) => group))
+
+  const replacementRoot = fields[0]
+  if (replacementRoot) {
+    visitFieldAndAncestors(replacementRoot, (field) => {
+      if (field._formGroup) affectedFormGroups.add(field._formGroup)
+    })
+  }
+
+  for (const group of affectedFormGroups) {
+    group._removeRoutedErrorFields(fieldsToReplace)
+  }
 
   for (const { group } of formGroups) {
     group._cancelValidation()

packages/form-core/src/FormGroupApi/FormGroupApi.lib.ts

@@ -578,6 +578,22 @@ export class InternalFormGroupApi<
     this._routedErrorFields = []
   }
 
+  // TODO: Remove this targeted cleanup when routed errors migrate to the new
+  // error state structure. Until then, replacement must drop stale field refs.
+  _removeRoutedErrorFields(fieldsToRemove: ReadonlySet<AnyInternalFieldApi>) {
+    for (let index = 0; index < this._routedErrorFields.length; index++) {
+      const fieldRefs = this._routedErrorFields[index]
+      if (!fieldRefs) continue
+
+      const liveFieldRefs = new Set(
+        Array.from(fieldRefs).filter((field) => !fieldsToRemove.has(field)),
+      )
+      if (liveFieldRefs.size !== fieldRefs.size) {
+        this._routedErrorFields[index] = liveFieldRefs
+      }
+    }
+  }
+
   _validate = async (
     signal: ConfigurableValidationTrigger | 'submit',
     opts?: { triggerFieldApi?: AnyInternalFieldApi },

packages/form-core/tests/FormGroupApi/FormGroupApi.spec.ts

@@ -388,6 +388,43 @@ describe('FormGroupApi', () => {
     await vi.waitFor(() => expect(validator).toHaveBeenCalledOnce())
   })
 
+  it('drops killed routed fields while preserving live routed fields', async () => {
+    const form = new InternalFormApi({
+      defaultValues: { guestDetails: { name: '', email: '' } },
+    })
+    const nameField = form._getOrCreateFieldApi({
+      name: 'guestDetails.name',
+    })
+    const emailField = form._getOrCreateFieldApi({
+      name: 'guestDetails.email',
+    })
+    const group = new InternalFormGroupApi({
+      form,
+      name: 'guestDetails',
+      validators: [
+        {
+          triggers: [],
+          run: () => ({
+            fields: {
+              name: 'Name is required',
+              email: 'Email is required',
+            },
+          }),
+        },
+      ],
+    })
+
+    await group.validate('submit')
+    expect(group._routedErrorFields[0]).toEqual(
+      new Set([nameField, emailField]),
+    )
+
+    form.deleteField('guestDetails.name')
+
+    expect(nameField._isKilled).toBe(true)
+    expect(group._routedErrorFields[0]).toEqual(new Set([emailField]))
+  })
+
   it('clears backing-node validation when cleanup cancels a group run', async () => {
     const validator = vi.fn(() => new Promise<null>(() => {}))
     const form = new InternalFormApi({