From 417bb2d31e5eaae08e0500a0525478606bfaea38 Mon Sep 17 00:00:00 2001
From: dakkar <dakkar@thenautilus.net>
Date: Sun, 11 Feb 2024 12:21:56 +0000
Subject: [PATCH] Never return broken notifications #409

Since notifications are stored in Redis, we can't expect relational
integrity: deleting a user will *not* delete notifications that
mention it.

But if we return notifications with missing bits (a `follow` without a
`user`, for example), the frontend will get very confused and throw an
exception while trying to render them.

This change makes sure we never expose those broken notifications. For
uniformity, I've applied the same logic to notes and roles mentioned
in notifications, even if nobody reported breakage in those cases.

Tested by creating a few types of notifications with a `notifierId`,
then deleting their user.

(cherry picked from commit 421f8d49e5d7a8dc3a798cc54716c767df8be3cb)
---
 .../entities/NotificationEntityService.ts     | 75 +++++++++++++++----
 1 file changed, 59 insertions(+), 16 deletions(-)

diff --git a/packages/backend/src/core/entities/NotificationEntityService.ts b/packages/backend/src/core/entities/NotificationEntityService.ts
index 0663898edbd5..a572fe320cdd 100644
--- a/packages/backend/src/core/entities/NotificationEntityService.ts
+++ b/packages/backend/src/core/entities/NotificationEntityService.ts
@@ -64,21 +64,38 @@ export class NotificationEntityService implements OnModuleInit {
 			packedNotes: Map<MiNote['id'], Packed<'Note'>>;
 			packedUsers: Map<MiUser['id'], Packed<'UserLite'>>;
 		},
-	): Promise<Packed<'Notification'>> {
+	): Promise<Packed<'Notification'> | null> {
 		const notification = src;
-		const noteIfNeed = NOTE_REQUIRED_NOTIFICATION_TYPES.has(notification.type) && 'noteId' in notification ? (
+		const needsNote = NOTE_REQUIRED_NOTIFICATION_TYPES.has(notification.type) && 'noteId' in notification;
+		const noteIfNeed = needsNote ? (
 			hint?.packedNotes != null
 				? hint.packedNotes.get(notification.noteId)
 				: this.noteEntityService.pack(notification.noteId, { id: meId }, {
 					detail: true,
 				})
 		) : undefined;
-		const userIfNeed = 'notifierId' in notification ? (
+		// if the note has been deleted, don't show this notification
+		if (needsNote && !noteIfNeed) {
+			return null;
+		}
+
+		const needsUser = 'notifierId' in notification;
+		const userIfNeed = needsUser ? (
 			hint?.packedUsers != null
 				? hint.packedUsers.get(notification.notifierId)
 				: this.userEntityService.pack(notification.notifierId, { id: meId })
 		) : undefined;
-		const role = notification.type === 'roleAssigned' ? await this.roleEntityService.pack(notification.roleId) : undefined;
+		// if the user has been deleted, don't show this notification
+		if (needsUser && !userIfNeed) {
+			return null;
+		}
+
+		const needsRole = notification.type === 'roleAssigned';
+		const role = needsRole ? await this.roleEntityService.pack(notification.roleId) : undefined;
+		// if the role has been deleted, don't show this notification
+		if (needsRole && !role) {
+			return null;
+		}
 
 		return await awaitAll({
 			id: notification.id,
@@ -141,10 +158,10 @@ export class NotificationEntityService implements OnModuleInit {
 			validNotifications = validNotifications.filter(x => (x.type !== 'receiveFollowRequest') || reqs.some(r => r.followerId === x.notifierId));
 		}
 
-		return await Promise.all(validNotifications.map(x => this.pack(x, meId, {}, {
+		return (await Promise.all(validNotifications.map(x => this.pack(x, meId, {}, {
 			packedNotes,
 			packedUsers,
-		})));
+		})))).filter(n => n);
 	}
 
 	@bindThis
@@ -159,23 +176,34 @@ export class NotificationEntityService implements OnModuleInit {
 			packedNotes: Map<MiNote['id'], Packed<'Note'>>;
 			packedUsers: Map<MiUser['id'], Packed<'UserLite'>>;
 		},
-	): Promise<Packed<'Notification'>> {
+	): Promise<Packed<'Notification'> | null> {
 		const notification = src;
-		const noteIfNeed = NOTE_REQUIRED_GROUPED_NOTIFICATION_TYPES.has(notification.type) && 'noteId' in notification ? (
+		const needsNote = NOTE_REQUIRED_GROUPED_NOTIFICATION_TYPES.has(notification.type) && 'noteId' in notification;
+		const noteIfNeed = needsNote ? (
 			hint?.packedNotes != null
 				? hint.packedNotes.get(notification.noteId)
 				: this.noteEntityService.pack(notification.noteId, { id: meId }, {
 					detail: true,
 				})
 		) : undefined;
-		const userIfNeed = 'notifierId' in notification ? (
+		// if the note has been deleted, don't show this notification
+		if (needsNote && !noteIfNeed) {
+			return null;
+		}
+
+		const needsUser = 'notifierId' in notification;
+		const userIfNeed = needsUser ? (
 			hint?.packedUsers != null
 				? hint.packedUsers.get(notification.notifierId)
 				: this.userEntityService.pack(notification.notifierId, { id: meId })
 		) : undefined;
+		// if the user has been deleted, don't show this notification
+		if (needsUser && !userIfNeed) {
+			return null;
+		}
 
 		if (notification.type === 'reaction:grouped') {
-			const reactions = await Promise.all(notification.reactions.map(async reaction => {
+			const reactions = (await Promise.all(notification.reactions.map(async reaction => {
 				const user = hint?.packedUsers != null
 					? hint.packedUsers.get(reaction.userId)!
 					: await this.userEntityService.pack(reaction.userId, { id: meId });
@@ -183,7 +211,12 @@ export class NotificationEntityService implements OnModuleInit {
 					user,
 					reaction: reaction.reaction,
 				};
-			}));
+			}))).filter(r => r.user);
+			// if all users have been deleted, don't show this notification
+			if (!reactions.length) {
+				return null;
+			}
+
 			return await awaitAll({
 				id: notification.id,
 				createdAt: new Date(notification.createdAt).toISOString(),
@@ -192,14 +225,19 @@ export class NotificationEntityService implements OnModuleInit {
 				reactions,
 			});
 		} else if (notification.type === 'renote:grouped') {
-			const users = await Promise.all(notification.userIds.map(userId => {
+			const users = (await Promise.all(notification.userIds.map(userId => {
 				const packedUser = hint?.packedUsers != null ? hint.packedUsers.get(userId) : null;
 				if (packedUser) {
 					return packedUser;
 				}
 
 				return this.userEntityService.pack(userId, { id: meId });
-			}));
+			}))).filter(u => u);
+			// if all users have been deleted, don't show this notification
+			if (!users.length) {
+				return null;
+			}
+
 			return await awaitAll({
 				id: notification.id,
 				createdAt: new Date(notification.createdAt).toISOString(),
@@ -209,7 +247,12 @@ export class NotificationEntityService implements OnModuleInit {
 			});
 		}
 
-		const role = notification.type === 'roleAssigned' ? await this.roleEntityService.pack(notification.roleId) : undefined;
+		const needsRole = notification.type === 'roleAssigned';
+		const role = needsRole ? await this.roleEntityService.pack(notification.roleId) : undefined;
+		// if the role has been deleted, don't show this notification
+		if (needsRole && !role) {
+			return null;
+		}
 
 		return await awaitAll({
 			id: notification.id,
@@ -277,9 +320,9 @@ export class NotificationEntityService implements OnModuleInit {
 			validNotifications = validNotifications.filter(x => (x.type !== 'receiveFollowRequest') || reqs.some(r => r.followerId === x.notifierId));
 		}
 
-		return await Promise.all(validNotifications.map(x => this.packGrouped(x, meId, {}, {
+		return (await Promise.all(validNotifications.map(x => this.packGrouped(x, meId, {}, {
 			packedNotes,
 			packedUsers,
-		})));
+		})))).filter(n => n);
 	}
 }