enhance: リモートのフォロワーから再度Followが来た場合、acceptを返してあげる

packages/backend/src/core/UserFollowingService.ts

@@ -30,6 +30,7 @@ import type { Config } from '@/config.js';
 import { AccountMoveService } from '@/core/AccountMoveService.js';
 import { UtilityService } from '@/core/UtilityService.js';
 import { FanoutTimelineService } from '@/core/FanoutTimelineService.js';
+import type { ThinUser } from '@/queue/types.js';
 import Logger from '../logger.js';
 
 const logger = new Logger('following/create');
@@ -94,20 +95,43 @@ export class UserFollowingService implements OnModuleInit {
 		this.userBlockingService = this.moduleRef.get('UserBlockingService');
 	}
 
+	@bindThis
+	public async deliverAccept(follower: MiRemoteUser, followee: MiPartialLocalUser, requestId?: string) {
+		const content = this.apRendererService.addContext(this.apRendererService.renderAccept(this.apRendererService.renderFollow(follower, followee, requestId), followee));
+		this.queueService.deliver(followee, content, follower.inbox, false);
+	}
+
+	/**
+	 * ThinUserでなくともユーザーの情報が最新でない場合はこちらを使うべき
+	 */
+	@bindThis
+	public async followByThinUser(
+		_follower: ThinUser,
+		_followee: ThinUser,
+		options: Parameters<typeof this.follow>[2] = {},
+	) {
+		const [follower, followee] = await Promise.all([
+			this.usersRepository.findOneByOrFail({ id: _follower.id }),
+			this.usersRepository.findOneByOrFail({ id: _followee.id }),
+		]) as [MiLocalUser | MiRemoteUser, MiLocalUser | MiRemoteUser];
+
+		await this.follow(follower, followee, options);
+	}
+
 	@bindThis
 	public async follow(
-		_follower: { id: MiUser['id'] },
-		_followee: { id: MiUser['id'] },
+		follower: MiLocalUser | MiRemoteUser,
+		followee: MiLocalUser | MiRemoteUser,
 		{ requestId, silent = false, withReplies }: {
 			requestId?: string,
 			silent?: boolean,
 			withReplies?: boolean,
 		} = {},
 	): Promise<void> {
-		const [follower, followee] = await Promise.all([
-			this.usersRepository.findOneByOrFail({ id: _follower.id }),
-			this.usersRepository.findOneByOrFail({ id: _followee.id }),
-		]) as [MiLocalUser | MiRemoteUser, MiLocalUser | MiRemoteUser];
+		if (this.userEntityService.isRemoteUser(follower) && this.userEntityService.isRemoteUser(followee)) {
+			// What?
+			throw new Error('Remote user cannot follow remote user.');
+		}
 
 		// check blocking
 		const [blocking, blocked] = await Promise.all([
@@ -129,6 +153,24 @@ export class UserFollowingService implements OnModuleInit {
 			if (blocked) throw new IdentifiableError('3338392a-f764-498d-8855-db939dcf8c48', 'blocked');
 		}
 
+		if (await this.followingsRepository.exists({
+			where: {
+				followerId: follower.id,
+				followeeId: followee.id,
+			},
+		})) {
+			// すでにフォロー関係が存在している場合
+			if (this.userEntityService.isRemoteUser(follower) && this.userEntityService.isLocalUser(followee)) {
+				// リモート → ローカル: acceptを送り返しておしまい
+				this.deliverAccept(follower, followee, requestId);
+				return;
+			}
+			if (this.userEntityService.isLocalUser(follower)) {
+				// ローカル → リモート/ローカル: 例外
+				throw new IdentifiableError('ec3f65c0-a9d1-47d9-8791-b2e7b9dcdced', 'already following');
+			}
+		}
+
 		const followeeProfile = await this.userProfilesRepository.findOneByOrFail({ userId: followee.id });
 		// フォロー対象が鍵アカウントである or
 		// フォロワーがBotであり、フォロー対象がBotからのフォローに慎重である or
@@ -189,8 +231,7 @@ export class UserFollowingService implements OnModuleInit {
 		await this.insertFollowingDoc(followee, follower, silent, withReplies);
 
 		if (this.userEntityService.isRemoteUser(follower) && this.userEntityService.isLocalUser(followee)) {
-			const content = this.apRendererService.addContext(this.apRendererService.renderAccept(this.apRendererService.renderFollow(follower, followee, requestId), followee));
-			this.queueService.deliver(followee, content, follower.inbox, false);
+			this.deliverAccept(follower, followee, requestId);
 		}
 	}
 
@@ -571,8 +612,7 @@ export class UserFollowingService implements OnModuleInit {
 		await this.insertFollowingDoc(followee, follower, false, request.withReplies);
 
 		if (this.userEntityService.isRemoteUser(follower) && this.userEntityService.isLocalUser(followee)) {
-			const content = this.apRendererService.addContext(this.apRendererService.renderAccept(this.apRendererService.renderFollow(follower, followee as MiPartialLocalUser, request.requestId!), followee));
-			this.queueService.deliver(followee, content, follower.inbox, false);
+			this.deliverAccept(follower, followee as MiPartialLocalUser, request.requestId ?? undefined);
 		}
 
 		this.userEntityService.pack(followee.id, followee, {

packages/backend/src/queue/processors/RelationshipProcessorService.ts

@@ -35,7 +35,7 @@ export class RelationshipProcessorService {
 	@bindThis
 	public async processFollow(job: Bull.Job<RelationshipJobData>): Promise<string> {
 		this.logger.info(`${job.data.from.id} is trying to follow ${job.data.to.id} ${job.data.withReplies ? "with replies" : "without replies"}`);
-		await this.userFollowingService.follow(job.data.from, job.data.to, {
+		await this.userFollowingService.followByThinUser(job.data.from, job.data.to, {
 			requestId: job.data.requestId,
 			silent: job.data.silent,
 			withReplies: job.data.withReplies,

packages/backend/src/server/api/endpoints/following/create.ts

@@ -100,22 +100,11 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				throw err;
 			});
 
-			// Check if already following
-			const exist = await this.followingsRepository.exists({
-				where: {
-					followerId: follower.id,
-					followeeId: followee.id,
-				},
-			});
-
-			if (exist) {
-				throw new ApiError(meta.errors.alreadyFollowing);
-			}
-
 			try {
 				await this.userFollowingService.follow(follower, followee, { withReplies: ps.withReplies });
 			} catch (e) {
 				if (e instanceof IdentifiableError) {
+					if (e.id === 'ec3f65c0-a9d1-47d9-8791-b2e7b9dcdced') throw new ApiError(meta.errors.alreadyFollowing);
 					if (e.id === '710e8fb0-b8c3-4922-be49-d5d93d8e6a6e') throw new ApiError(meta.errors.blocking);
 					if (e.id === '3338392a-f764-498d-8855-db939dcf8c48') throw new ApiError(meta.errors.blocked);
 				}