fix(ui): cannot filter by virtual relationship fields in WhereBuilder (#13686)

### What?
- Fixed an issue where virtual relationship fields (`virtual: string`,
e.g. `post.title`) could not be used in the WhereBuilder filter
dropdown.
- Ensured regular virtual fields (`virtual: true`) are still excluded
since they are not backed by database fields.

### Why?
Previously, attempting to filter by a virtual relationship caused
runtime errors because the field was treated as a plain text field. At
the same time, non-queryable virtuals needed to remain excluded to avoid
invalid queries.

### How?
- Updated `reduceFieldsToOptions` to recognize `virtual: string` fields
and map them to their underlying path while keeping their declared type
and operators.
- Continued to filter out `virtual: true` fields in the same guard used
for hidden/disabled fields.

test/admin/collections/Virtuals.ts

@@ -0,0 +1,27 @@
+import type { CollectionConfig } from 'payload'
+
+import { virtualsSlug } from '../slugs.js'
+
+export const Virtuals: CollectionConfig = {
+  slug: virtualsSlug,
+  admin: {
+    useAsTitle: 'virtualTitleFromPost',
+  },
+  fields: [
+    {
+      name: 'virtualTitleFromPost',
+      type: 'text',
+      virtual: 'post.title',
+    },
+    {
+      name: 'virtualText',
+      type: 'text',
+      virtual: true,
+    },
+    {
+      name: 'post',
+      type: 'relationship',
+      relationTo: 'posts',
+    },
+  ],
+}

test/admin/config.ts

@@ -28,6 +28,7 @@ import { UploadCollection } from './collections/Upload.js'
 import { UploadTwoCollection } from './collections/UploadTwo.js'
 import { UseAsTitleGroupField } from './collections/UseAsTitleGroupField.js'
 import { Users } from './collections/Users.js'
+import { Virtuals } from './collections/Virtuals.js'
 import { with300Documents } from './collections/With300Documents.js'
 import { CustomGlobalViews1 } from './globals/CustomViews1.js'
 import { CustomGlobalViews2 } from './globals/CustomViews2.js'
@@ -187,6 +188,7 @@ export default buildConfigWithDefaults({
     UseAsTitleGroupField,
     DisableBulkEdit,
     CustomListDrawer,
+    Virtuals,
   ],
   globals: [
     GlobalHidden,

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

@@ -4,7 +4,7 @@ import { expect, test } from '@playwright/test'
 import { mapAsync } from 'payload'
 import * as qs from 'qs-esm'
 
-import type { Config, Geo, Post } from '../../payload-types.js'
+import type { Config, Geo, Post, Virtual } from '../../payload-types.js'
 
 import {
   ensureCompilationIsDone,
@@ -23,6 +23,7 @@ import {
   listDrawerSlug,
   placeholderCollectionSlug,
   postsCollectionSlug,
+  virtualsSlug,
   with300DocumentsSlug,
 } from '../../slugs.js'
 
@@ -70,6 +71,7 @@ describe('List View', () => {
   let placeholderUrl: AdminUrlUtil
   let disableBulkEditUrl: AdminUrlUtil
   let user: any
+  let virtualsUrl: AdminUrlUtil
 
   let serverURL: string
   let adminRoutes: ReturnType<typeof getRoutes>
@@ -94,6 +96,7 @@ describe('List View', () => {
     withListViewUrl = new AdminUrlUtil(serverURL, listDrawerSlug)
     placeholderUrl = new AdminUrlUtil(serverURL, placeholderCollectionSlug)
     disableBulkEditUrl = new AdminUrlUtil(serverURL, 'disable-bulk-edit')
+    virtualsUrl = new AdminUrlUtil(serverURL, virtualsSlug)
     const context = await browser.newContext()
     page = await context.newPage()
     initPageConsoleErrorCatch(page)
@@ -416,6 +419,44 @@ describe('List View', () => {
       ).toBeVisible()
     })
 
+    test('should not allow search by virtual: true field in field dropdown', async () => {
+      await page.goto(virtualsUrl.list)
+
+      await openListFilters(page, {})
+
+      const whereBuilder = page.locator('.where-builder')
+      await whereBuilder.locator('.where-builder__add-first-filter').click()
+
+      const conditionField = whereBuilder.locator('.condition__field')
+      await conditionField.click()
+
+      const menuList = conditionField.locator('.rs__menu-list')
+
+      // ensure the virtual field is not present
+      await expect(menuList.locator('div', { hasText: exactText('Virtual Text') })).toHaveCount(0)
+    })
+
+    test('should allow to filter by virtual relationship field', async () => {
+      const post1 = await createPost({ title: 'somePost' })
+      const post2 = await createPost({ title: 'otherPost' })
+
+      await createVirtualDoc({ post: post1.id })
+      await createVirtualDoc({ post: post2.id })
+
+      await page.goto(virtualsUrl.list)
+
+      await expect(page.locator(tableRowLocator)).toHaveCount(2)
+
+      await addListFilter({
+        page,
+        fieldLabel: 'Virtual Title From Post',
+        operatorLabel: 'equals',
+        value: 'somePost',
+      })
+
+      await expect(page.locator(tableRowLocator)).toHaveCount(1)
+    })
+
     test('should allow to filter in array field', async () => {
       await createArray()
 
@@ -1786,3 +1827,13 @@ async function createArray() {
     },
   })
 }
+
+async function createVirtualDoc(overrides?: Partial<Virtual>): Promise<Virtual> {
+  return payload.create({
+    collection: virtualsSlug,
+    data: {
+      post: overrides?.post,
+      ...overrides,
+    },
+  }) as unknown as Promise<Virtual>
+}

test/admin/payload-types.ts

@@ -94,6 +94,7 @@ export interface Config {
     'use-as-title-group-field': UseAsTitleGroupField;
     'disable-bulk-edit': DisableBulkEdit;
     'custom-list-drawer': CustomListDrawer;
+    virtuals: Virtual;
     'payload-locked-documents': PayloadLockedDocument;
     'payload-preferences': PayloadPreference;
     'payload-migrations': PayloadMigration;
@@ -127,6 +128,7 @@ export interface Config {
     'use-as-title-group-field': UseAsTitleGroupFieldSelect<false> | UseAsTitleGroupFieldSelect<true>;
     'disable-bulk-edit': DisableBulkEditSelect<false> | DisableBulkEditSelect<true>;
     'custom-list-drawer': CustomListDrawerSelect<false> | CustomListDrawerSelect<true>;
+    virtuals: VirtualsSelect<false> | VirtualsSelect<true>;
     'payload-locked-documents': PayloadLockedDocumentsSelect<false> | PayloadLockedDocumentsSelect<true>;
     'payload-preferences': PayloadPreferencesSelect<false> | PayloadPreferencesSelect<true>;
     'payload-migrations': PayloadMigrationsSelect<false> | PayloadMigrationsSelect<true>;
@@ -582,6 +584,18 @@ export interface CustomListDrawer {
   updatedAt: string;
   createdAt: string;
 }
+/**
+ * This interface was referenced by `Config`'s JSON-Schema
+ * via the `definition` "virtuals".
+ */
+export interface Virtual {
+  id: string;
+  virtualTitleFromPost?: string | null;
+  virtualText?: string | null;
+  post?: (string | null) | Post;
+  updatedAt: string;
+  createdAt: string;
+}
 /**
  * This interface was referenced by `Config`'s JSON-Schema
  * via the `definition` "payload-locked-documents".
@@ -696,6 +710,10 @@ export interface PayloadLockedDocument {
     | ({
         relationTo: 'custom-list-drawer';
         value: string | CustomListDrawer;
+      } | null)
+    | ({
+        relationTo: 'virtuals';
+        value: string | Virtual;
       } | null);
   globalSlug?: string | null;
   user: {
@@ -1111,6 +1129,17 @@ export interface CustomListDrawerSelect<T extends boolean = true> {
   updatedAt?: T;
   createdAt?: T;
 }
+/**
+ * This interface was referenced by `Config`'s JSON-Schema
+ * via the `definition` "virtuals_select".
+ */
+export interface VirtualsSelect<T extends boolean = true> {
+  virtualTitleFromPost?: T;
+  virtualText?: T;
+  post?: T;
+  updatedAt?: T;
+  createdAt?: T;
+}
 /**
  * This interface was referenced by `Config`'s JSON-Schema
  * via the `definition` "payload-locked-documents_select".

test/admin/slugs.ts

@@ -23,6 +23,7 @@ export const uploadTwoCollectionSlug = 'uploads-two'
 export const customFieldsSlug = 'custom-fields'
 
 export const listDrawerSlug = 'with-list-drawer'
+export const virtualsSlug = 'virtuals'
 export const collectionSlugs = [
   usersCollectionSlug,
   customViews1CollectionSlug,
@@ -39,6 +40,7 @@ export const collectionSlugs = [
   customFieldsSlug,
   disableDuplicateSlug,
   listDrawerSlug,
+  virtualsSlug,
 ]
 
 export const customGlobalViews1GlobalSlug = 'custom-global-views-one'