[2.x] fix: image preview shows empty src in composer preview

[imorland]

Problem

After the thumbnail feature (PR #465), uploading an image with the image-preview template showed a broken image (src="") in the composer live preview:

<img class="FoFUpload--Upl-Image-Preview" src="" ...>

Root cause

The preview() method in ImagePreviewTemplate generates the BBCode string that the JavaScript TextFormatter renderer uses for the composer preview (the live preview while typing, before the post is submitted). It was not including thumbnail_url:

// Before
return "[upl-image-preview uuid={$file->uuid} url={$file->url} alt={$file->base_name}]";

The image-preview blade template uses {@thumbnail_url} as the <img src>. Since thumbnail_url was absent from the BBCode, the JS renderer set src="".

The PHP FormatImagePreview renderer (which properly injects thumbnail_url) only runs at post save/render time — not during the composer live preview.

Fix

Include thumbnail_url in the preview BBCode, using $file->thumbnail_url (the stored thumbnail) falling back to $file->url (the original file URL):

$thumbnailUrl = $file->thumbnail_url ?: $file->url;
return "[upl-image-preview uuid={$file->uuid} url={$file->url} alt={$file->base_name} thumbnail_url={$thumbnailUrl}]";

Forums without thumbnails generated (e.g. before running the backfill command) will show the full-resolution image in the preview, matching the pre-thumbnail behaviour.

🤖 Generated with Claude Code