fix(ui): ensure file field is only serialized at top-level for upload-enabled collections (#12074)

This fixes an issue where fields with the name `file` was being
serialized as a top-level field in multipart form data even when the
collection was not upload-enabled. This caused the value of `file` (when
used as a regular field like a text, array, etc.) to be stripped from
the `_payload`.

- Updated `createFormData` to only delete `data.file` and serialize it
at the top level if `docConfig.upload` is defined.
- This prevents unintended loss of `file` field values for non-upload
collections.

The `file` field now remains safely nested in `_payload` unless it's
part of an upload-enabled collection.

packages/ui/src/forms/Form/index.tsx

@@ -56,7 +56,8 @@ import { initContextState } from './initContextState.js'
 const baseClass = 'form'
 
 export const Form: React.FC<FormProps> = (props) => {
-  const { id, collectionSlug, docPermissions, getDocPreferences, globalSlug } = useDocumentInfo()
+  const { id, collectionSlug, docConfig, docPermissions, getDocPreferences, globalSlug } =
+    useDocumentInfo()
 
   const {
     action,
@@ -491,8 +492,28 @@ export const Form: React.FC<FormProps> = (props) => {
 
       let file = data?.file
 
-      if (file) {
+      if (docConfig && 'upload' in docConfig && docConfig.upload && file) {
         delete data.file
+
+        const handler = getUploadHandler({ collectionSlug })
+
+        if (typeof handler === 'function') {
+          let filename = file.name
+          const clientUploadContext = await handler({
+            file,
+            updateFilename: (value) => {
+              filename = value
+            },
+          })
+
+          file = JSON.stringify({
+            clientUploadContext,
+            collectionSlug,
+            filename,
+            mimeType: file.type,
+            size: file.size,
+          })
+        }
       }
 
       if (mergeOverrideData) {
@@ -504,37 +525,23 @@ export const Form: React.FC<FormProps> = (props) => {
         data = overrides
       }
 
-      const handler = getUploadHandler({ collectionSlug })
-
-      if (file && typeof handler === 'function') {
-        let filename = file.name
-        const clientUploadContext = await handler({
-          file,
-          updateFilename: (value) => {
-            filename = value
-          },
-        })
-
-        file = JSON.stringify({
-          clientUploadContext,
-          collectionSlug,
-          filename,
-          mimeType: file.type,
-          size: file.size,
-        })
+      const dataToSerialize: Record<string, unknown> = {
+        _payload: JSON.stringify(data),
       }
 
-      const dataToSerialize = {
-        _payload: JSON.stringify(data),
-        file,
+      if (docConfig && 'upload' in docConfig && docConfig.upload && file) {
+        dataToSerialize.file = file
       }
 
       // nullAsUndefineds is important to allow uploads and relationship fields to clear themselves
-      const formData = serialize(dataToSerialize, { indices: true, nullsAsUndefineds: false })
+      const formData = serialize(dataToSerialize, {
+        indices: true,
+        nullsAsUndefineds: false,
+      })
 
       return formData
     },
-    [collectionSlug, getUploadHandler],
+    [collectionSlug, docConfig, getUploadHandler],
   )
 
   const reset = useCallback(

test/admin/collections/Posts.ts

@@ -236,6 +236,10 @@ export const Posts: CollectionConfig = {
         },
       ],
     },
+    {
+      name: 'file',
+      type: 'text',
+    },
   ],
   labels: {
     plural: slugPluralLabel,

test/admin/e2e/document-view/e2e.spec.ts

@@ -512,6 +512,17 @@ describe('Document View', () => {
       await expect(publishButton).toContainText('Publish in English')
     })
   })
+
+  describe('reserved field names', () => {
+    test('should allow creation of field named file in non-upload enabled collection', async () => {
+      await page.goto(postsUrl.create)
+      const fileField = page.locator('#field-file')
+      await fileField.fill('some file text')
+      await saveDocAndAssert(page)
+
+      await expect(fileField).toHaveValue('some file text')
+    })
+  })
 })
 
 async function createPost(overrides?: Partial<Post>): Promise<Post> {

test/admin/payload-types.ts

@@ -247,6 +247,7 @@ export interface Post {
   sidebarField?: string | null;
   wavelengths?: ('fm' | 'am') | null;
   selectField?: ('option1' | 'option2')[] | null;
+  file?: string | null;
   updatedAt: string;
   createdAt: string;
   _status?: ('draft' | 'published') | null;
@@ -665,6 +666,7 @@ export interface PostsSelect<T extends boolean = true> {
   sidebarField?: T;
   wavelengths?: T;
   selectField?: T;
+  file?: T;
   updatedAt?: T;
   createdAt?: T;
   _status?: T;