There is no way to refresh the composer's preview except by modifying its content about framework

[SychO9]

It's not clear to me what it is you're trying to do or why you need an async call in the filter. I don't consider this a bug at the moment, it seems more like feature.

Can you please explain your use case.

[n-peugnet]

I don't consider this a bug at the moment, it seems more like feature.

Sorry you're right, this is not exactly a bug request. But as it was a technical request for the extension API, the bug tracker seemed more adequate.

It's not clear to me what it is you're trying to do or why you need an async call in the filter.
Can you please explain your use case.

I am writing an extension that modifies the content of CommentPosts. Among other features, it replaces bare links to discussions into a link that contains the title of the discussion. For now this is done in the frontend.

To make the modifications in the backend instead, and to get a preview of the modifications while writing a post, I figured that I needed to add a TextFormatter configuration (club-1/flarum-ext-cross-references#4).

As explained in s9e/TextFormatter#208, I need to make an asynchronous call in the Javascript part of the filter, in order to fetch the title of the discussion from the API (using app.store.find()). But TextFormatter filters only works synchronously, so I was pointed to refreshing the preview once the Promise resolves.

This is indeed working, as I tried to modify the content of the composer using app.composer.editor.insertAt() to trigger a refresh. But I would need to refresh the preview without editing the content of the composer.

From what I see here (ligne 40) there seem to be no way to trigger a refresh with an unchanged content:

framework/framework/core/js/src/forum/components/ComposerPostPreview.js

Lines 33 to 45 in fe8480c

	const updatePreview = () => {
	// Since we're polling, the composer may have been closed in the meantime,
	// so we bail in that case.
	if (!this.attrs.composer.isVisible()) return;
	const content = this.attrs.composer.fields.content();
	if (preview === content) return;
	preview = content;
	this.attrs.surround(() => s9e.TextFormatter.preview(preview || '', vnode.dom));
	};