fix(admin): resolve and display current product image

Form state for the images array only holds the media ID, not the
populated doc. Read images.0.image via useField, then fetch
/api/media/<id> to resolve url+alt for display. On upload, add a new
row via dispatchFields if the array is empty, otherwise update in
place.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

nextjs/src/components/admin/ImageUploadSlot.tsx

@@ -1,29 +1,58 @@
 'use client'
 
-import { useField } from '@payloadcms/ui'
-import { useRef, useState } from 'react'
+import { useField, useForm } from '@payloadcms/ui'
+import { useEffect, useRef, useState } from 'react'
 
 type MediaDoc = { id: number | string; url?: string | null; alt?: string | null }
-type ImageEntry = { id?: string; image?: MediaDoc | string | null } | null | undefined
 
 type Props = {
   displayName?: string
 }
 
-function resolveFirstImage(entries: ImageEntry[] | undefined | null): { url: string; alt: string } {
-  const first = entries?.[0]?.image
-  if (!first) return { url: '', alt: '' }
-  if (typeof first === 'string') return { url: '', alt: '' }
-  return { url: first.url ?? '', alt: first.alt ?? '' }
+function extractMediaId(value: unknown): string | number | null {
+  if (value == null) return null
+  if (typeof value === 'number' || typeof value === 'string') return value
+  if (typeof value === 'object' && 'id' in (value as object)) {
+    return (value as { id: number | string }).id ?? null
+  }
+  return null
 }
 
 export function ImageUploadSlot({ displayName }: Props) {
-  const { value: images, setValue } = useField<ImageEntry[]>({ path: 'images' })
+  const { value: mediaValue, setValue: setMedia } = useField<unknown>({ path: 'images.0.image' })
+  const { dispatchFields } = useForm()
   const fileInput = useRef<HTMLInputElement | null>(null)
   const [uploading, setUploading] = useState(false)
   const [error, setError] = useState<string | null>(null)
+  const [resolved, setResolved] = useState<MediaDoc | null>(null)
 
-  const { url, alt } = resolveFirstImage(images)
+  const mediaId = extractMediaId(mediaValue)
+
+  useEffect(() => {
+    let cancelled = false
+    if (mediaId == null) {
+      setResolved(null)
+      return
+    }
+    if (resolved && resolved.id === mediaId) return
+    if (mediaValue && typeof mediaValue === 'object' && 'url' in (mediaValue as object)) {
+      setResolved(mediaValue as MediaDoc)
+      return
+    }
+    ;(async () => {
+      try {
+        const res = await fetch(`/api/media/${mediaId}`, { credentials: 'include' })
+        if (!res.ok) return
+        const doc = await res.json()
+        if (!cancelled) setResolved({ id: doc.id, url: doc.url, alt: doc.alt })
+      } catch {
+        /* ignore */
+      }
+    })()
+    return () => {
+      cancelled = true
+    }
+  }, [mediaId, mediaValue, resolved])
 
   const onPick = () => fileInput.current?.click()
 
@@ -40,9 +69,19 @@ export function ImageUploadSlot({ displayName }: Props) {
       const res = await fetch('/api/media', { method: 'POST', body: fd, credentials: 'include' })
       if (!res.ok) throw new Error(`upload ${res.status}`)
       const { doc } = await res.json()
-      const media: MediaDoc = { id: doc.id, url: doc.url, alt: doc.alt }
-      const next = [{ image: media }, ...(images ?? []).slice(1)]
-      setValue(next)
+      if (mediaId == null) {
+        dispatchFields({
+          type: 'ADD_ROW',
+          path: 'images',
+          rowIndex: 0,
+          subFieldState: {
+            image: { initialValue: doc.id, valid: true, value: doc.id },
+          },
+        })
+      } else {
+        setMedia(doc.id)
+      }
+      setResolved({ id: doc.id, url: doc.url, alt: doc.alt })
     } catch (err) {
       setError(err instanceof Error ? err.message : 'upload failed')
     } finally {
@@ -50,10 +89,13 @@ export function ImageUploadSlot({ displayName }: Props) {
     }
   }
 
+  const url = resolved?.url ?? ''
+  const alt = resolved?.alt ?? displayName ?? 'Produit'
+
   return (
     <div className="rebours-admin-panel__img-slot" onClick={onPick} role="button" tabIndex={0}>
       {url ? (
-        <img src={url} alt={alt || displayName || 'Produit'} />
+        <img src={url} alt={alt} />
       ) : (
         <div className="rebours-admin-panel__img-placeholder">
           Cliquez pour<br />uploader une image