fix(gateway): accept Kakao already-registered response

app/gateway-api/src/auth/kakaoClient.ts

@@ -25,6 +25,11 @@ export interface KakaoUserInfo {
     kakaoAccount: KakaoAccountInfo;
 }
 
+export interface KakaoSignupResult {
+    id?: string;
+    alreadyRegistered: boolean;
+}
+
 const buildForm = (params: Record<string, string>): URLSearchParams => {
     const form = new URLSearchParams();
     for (const [key, value] of Object.entries(params)) {
@@ -106,19 +111,24 @@ export class KakaoOAuthClient {
         return parseToken(payload);
     }
 
-    async signup(accessToken: string): Promise<{ id?: string; msg?: string }> {
+    async signup(accessToken: string): Promise<KakaoSignupResult> {
         const response = await fetch(new URL('/v1/user/signup', this.apiHost), {
             headers: {
                 Authorization: `Bearer ${accessToken}`,
             },
         });
         const payload = (await response.json()) as Record<string, unknown>;
+        if (!response.ok && payload.code === -102 && payload.msg === 'already registered') {
+            return {
+                alreadyRegistered: true,
+            };
+        }
         if (!response.ok) {
             throw new Error(`Kakao signup error: ${JSON.stringify(payload)}`);
         }
         return {
             id: payload.id ? String(payload.id) : undefined,
-            msg: payload.msg ? String(payload.msg) : undefined,
+            alreadyRegistered: false,
         };
     }
 

app/gateway-api/src/router.ts

@@ -253,7 +253,7 @@ export const appRouter = router({
                 const tokenIssuedAt = new Date();
 
                 const signupResult = await ctx.kakaoClient.signup(token.accessToken);
-                const alreadyRegisteredWithKakao = !signupResult.id && signupResult.msg === 'already registered';
+                const alreadyRegisteredWithKakao = !signupResult.id && signupResult.alreadyRegistered;
                 if (!signupResult.id && !alreadyRegisteredWithKakao) {
                     throw new TRPCError({
                         code: 'BAD_REQUEST',

app/gateway-api/test/authFlow.test.ts

@@ -71,7 +71,9 @@ const buildCaller = (
             };
         },
         signup: async () =>
-            options.kakaoSignupAlreadyRegistered ? { msg: 'already registered' as const } : { id: kakaoProfile.id },
+            options.kakaoSignupAlreadyRegistered
+                ? { alreadyRegistered: true }
+                : { id: kakaoProfile.id, alreadyRegistered: false },
         getMe: async () => ({
             id: kakaoProfile.id,
             kakaoAccount: {

app/gateway-api/test/kakaoClient.test.ts

@@ -0,0 +1,47 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+import { KakaoOAuthClient } from '../src/auth/kakaoClient.js';
+
+const createClient = (): KakaoOAuthClient =>
+    new KakaoOAuthClient({
+        restKey: 'rest-key',
+        redirectUri: 'https://gateway.example.test/oauth/callback',
+        apiHost: 'https://kapi.example.test',
+    });
+
+describe('Kakao OAuth HTTP transport', () => {
+    afterEach(() => {
+        vi.restoreAllMocks();
+    });
+
+    it('normalizes Kakao -102 already registered errors into an account recovery result', async () => {
+        const fetchMock = vi.spyOn(globalThis, 'fetch').mockResolvedValueOnce(
+            new Response(JSON.stringify({ msg: 'already registered', code: -102 }), {
+                status: 400,
+                headers: { 'Content-Type': 'application/json' },
+            })
+        );
+
+        await expect(createClient().signup('access-token')).resolves.toEqual({
+            alreadyRegistered: true,
+        });
+        expect(fetchMock).toHaveBeenCalledWith(new URL('https://kapi.example.test/v1/user/signup'), {
+            headers: {
+                Authorization: 'Bearer access-token',
+            },
+        });
+    });
+
+    it('continues to reject unrelated Kakao signup errors', async () => {
+        vi.spyOn(globalThis, 'fetch').mockResolvedValueOnce(
+            new Response(JSON.stringify({ msg: 'invalid request', code: -201 }), {
+                status: 400,
+                headers: { 'Content-Type': 'application/json' },
+            })
+        );
+
+        await expect(createClient().signup('access-token')).rejects.toThrow(
+            'Kakao signup error: {"msg":"invalid request","code":-201}'
+        );
+    });
+});