fix(backend): correct invalid schema format specifying only `required` for `anyOf` (#16089)

* fix(backend): correct invalid schema format specifying only `required` for `anyOf`

* refactor(backend): make types derived from `allOf` or `anyOf` more strong

1 files changed, 33 insertions, 18 deletions

diff --git a/packages/backend/src/server/api/endpoints/users/followers.ts b/packages/backend/src/server/api/endpoints/users/followers.ts
index a8b4319a61..bb8d4c49e9 100644
--- a/packages/backend/src/server/api/endpoints/users/followers.ts
+++ b/packages/backend/src/server/api/endpoints/users/followers.ts
@@ -47,23 +47,38 @@ export const meta = {
 } as const;
 
 export const paramDef = {
-	type: 'object',
-	properties: {
-		sinceId: { type: 'string', format: 'misskey:id' },
-		untilId: { type: 'string', format: 'misskey:id' },
-		limit: { type: 'integer', minimum: 1, maximum: 100, default: 10 },
-
-		userId: { type: 'string', format: 'misskey:id' },
-		username: { type: 'string' },
-		host: {
-			type: 'string',
-			nullable: true,
-			description: 'The local host is represented with `null`.',
+	allOf: [
+		{
+			anyOf: [
+				{
+					type: 'object',
+					properties: {
+						userId: { type: 'string', format: 'misskey:id' },
+					},
+					required: ['userId'],
+				},
+				{
+					type: 'object',
+					properties: {
+						username: { type: 'string' },
+						host: {
+							type: 'string',
+							nullable: true,
+							description: 'The local host is represented with `null`.',
+						},
+					},
+					required: ['username', 'host'],
+				},
+			],
+		},
+		{
+			type: 'object',
+			properties: {
+				sinceId: { type: 'string', format: 'misskey:id' },
+				untilId: { type: 'string', format: 'misskey:id' },
+				limit: { type: 'integer', minimum: 1, maximum: 100, default: 10 },
+			},
 		},
-	},
-	anyOf: [
-		{ required: ['userId'] },
-		{ required: ['username', 'host'] },
 	],
 } as const;
 
@@ -85,9 +100,9 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private roleService: RoleService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
-			const user = await this.usersRepository.findOneBy(ps.userId != null
+			const user = await this.usersRepository.findOneBy('userId' in ps
 				? { id: ps.userId }
-				: { usernameLower: ps.username!.toLowerCase(), host: this.utilityService.toPunyNullable(ps.host) ?? IsNull() });
+				: { usernameLower: ps.username.toLowerCase(), host: this.utilityService.toPunyNullable(ps.host) ?? IsNull() });
 
 			if (user == null) {
 				throw new ApiError(meta.errors.noSuchUser);