fix: correctly render empty note text (#8746)

Ensure that the _misskey_content attribute will always exist. Because
the API endpoint does not require the existence of the `text` field,
that field may be `undefined`. By using `?? null` it can be ensured
that the value is at least `null`.

Furthermore, the rendered HTML of a note with empty text will also be
the empty string. From git blame it seems that this behaviour was added
because of a Mastodon bug that might have previously existed. Hoever,
this seems to be no longer the case as I can find mastodon posts that
have empty content.

The code could be made a bit more succinct by using the null coercion
operator.

2 files changed, 5 insertions, 7 deletions

diff --git a/packages/backend/src/remote/activitypub/misc/get-note-html.ts b/packages/backend/src/remote/activitypub/misc/get-note-html.ts
index 3800b40608..389039ebed 100644
--- a/packages/backend/src/remote/activitypub/misc/get-note-html.ts
+++ b/packages/backend/src/remote/activitypub/misc/get-note-html.ts
@@ -3,8 +3,6 @@ import { Note } from '@/models/entities/note.js';
 import { toHtml } from '../../../mfm/to-html.js';
 
 export default function(note: Note) {
-	let html = note.text ? toHtml(mfm.parse(note.text), JSON.parse(note.mentionedRemoteUsers)) : null;
-	if (html == null) html = '<p>.</p>';
-
-	return html;
+	if (!note.text) return '';
+	return toHtml(mfm.parse(note.text), JSON.parse(note.mentionedRemoteUsers));
 }
diff --git a/packages/backend/src/remote/activitypub/renderer/note.ts b/packages/backend/src/remote/activitypub/renderer/note.ts
index e8d429e5de..b7df0e9a39 100644
--- a/packages/backend/src/remote/activitypub/renderer/note.ts
+++ b/packages/backend/src/remote/activitypub/renderer/note.ts
@@ -82,15 +82,15 @@ export default async function renderNote(note: Note, dive = true, isTalk = false
 
 	const files = await getPromisedFiles(note.fileIds);
 
-	const text = note.text;
+	// text should never be undefined
+	const text = note.text ?? null;
 	let poll: Poll | null = null;
 
 	if (note.hasPoll) {
 		poll = await Polls.findOneBy({ noteId: note.id });
 	}
 
-	let apText = text;
-	if (apText == null) apText = '';
+	let apText = text ?? '';
 
 	if (quote) {
 		apText += `\n\nRE: ${quote}`;