Carousel / Saved Templates: Poster generation not working

[swissspidy]

Bug Description

While looking at #12512 I noticed that the poster images for saved templates are no longer generated/uploaded.

Expected Behaviour

When saving a page as template, we ought to take a poster image and upload that to WP. But this doesn't seem to be happening anymore.

Code in question:

web-stories-wp/packages/story-editor/src/components/library/panes/pageTemplates/savedPageTemplate.js

Lines 130 to 176 in 896cfe7

	const imageUrl = page.image?.url || pageDataUrl;
	const shouldPostBlob =
	hasUploadMediaAction && pageDataUrl && !page.image?.url;
	useEffect(() => {
	if (!shouldPostBlob) {
	return;
	}
	(async () => {
	try {
	const blob = await fetchRemoteBlob(pageDataUrl);
	const file = blobToFile(
	blob,
	`web-stories-page-template-${page.templateId}.jpg`,
	'image/jpeg'
	);
	const resource = await uploadFile(file, {
	templateId: page.templateId,
	mediaSource: 'page-template',
	});
	updatePageTemplate(page.templateId, {
	featured_media: resource.id,
	});
	updateSavedTemplate({
	templateId: page.templateId,
	image: {
	id: resource.id,
	height: resource.height,
	width: resource.width,
	url: resource.src,
	},
	});
	} catch (err) {
	// Catch upload errors, e.g. if the file is too large,
	// so that the page template can still be added, albeit without an image.
	trackError('upload_generated_page_template_image', err?.message);
	}
	})();
	}, [
	pageDataUrl,
	uploadFile,
	updatePageTemplate,
	page.templateId,
	shouldPostBlob,
	updateSavedTemplate,
	]);

Steps to Reproduce

1. Save current page as template
2. Notice lack of network requests to upload poster image
3. Check DOM to see that no image has been uploaded

Screenshots

Additional Context

• Plugin Version: 1.25
• WordPress Version:
• Operating System:
• Browser:

[swissspidy]

This seems to hang somewhere in storyPageToDataUrl, with the htmlToImage.toJpeg call seemingly never resolving.

I noticed that this issue not only affects saved templates, but also the carousel in the workspace. No images are ever created.

[merapi]

Fix is already on main, tested on local env and staging.