fix(adapter-nextjs): duplicate response Set-Cookie headers in pages router

packages/adapter-nextjs/__tests__/utils/createCookieStorageAdapterFromNextServerContext.test.ts

@@ -412,6 +412,41 @@ describe('createCookieStorageAdapterFromNextServerContext', () => {
 				'key3=;Expires=Thu, 01 Jan 1970 00:00:00 GMT',
 			]);
 		});
+
+		it('does not add duplicate cookies when the cookies are defined in the response Set-Cookie headers', () => {
+			const mockExistingSetCookieValues = [
+				'CognitoIdentityServiceProvider.1234.accessToken=1234;Path=/',
+				'CognitoIdentityServiceProvider.1234.refreshToken=1234;Path=/',
+				'CognitoIdentityServiceProvider.1234.identityId=;Expires=Thu, 01 Jan 1970 00:00:00 GMT',
+			];
+
+			const request = new IncomingMessage(new Socket());
+			const response = new ServerResponse(request);
+			const appendHeaderSpy = jest.spyOn(response, 'appendHeader');
+			const getHeaderSpy = jest.spyOn(response, 'getHeader');
+
+			Object.defineProperty(request, 'cookies', {
+				get() {
+					return {};
+				},
+			});
+
+			getHeaderSpy.mockReturnValue(mockExistingSetCookieValues);
+
+			const result = createCookieStorageAdapterFromNextServerContext({
+				request: request as any,
+				response,
+			});
+
+			result.set('CognitoIdentityServiceProvider.1234.accessToken', '5678');
+			expect(appendHeaderSpy).not.toHaveBeenCalled();
+
+			result.set('CognitoIdentityServiceProvider.1234.refreshToken', '5678');
+			expect(appendHeaderSpy).not.toHaveBeenCalled();
+
+			result.delete('CognitoIdentityServiceProvider.1234.identityId');
+			expect(appendHeaderSpy).not.toHaveBeenCalled();
+		});
 	});
 
 	it('should throw error when no cookie storage adapter is created from the context', () => {

packages/adapter-nextjs/src/utils/createCookieStorageAdapterFromNextServerContext.ts

@@ -171,20 +171,44 @@ const createCookieStorageAdapterFromGetServerSidePropsContext = (
 			return allCookies;
 		},
 		set(name, value, options) {
+			const encodedName = ensureEncodedForJSCookie(name);
+
+			const existingValues = getExistingSetCookieValues(
+				response.getHeader('Set-Cookie'),
+			);
+
+			// if the cookies have already been set, we don't need to set them again.
+			if (
+				existingValues.findIndex(
+					cookieValue =>
+						cookieValue.startsWith(`${encodedName}=`) &&
+						!cookieValue.startsWith(`${encodedName}=;`),
+				) > -1
+			) {
+				return;
+			}
+
 			response.appendHeader(
 				'Set-Cookie',
-				`${ensureEncodedForJSCookie(name)}=${value};${
+				`${encodedName}=${value};${
 					options ? serializeSetCookieOptions(options) : ''
 				}`,
 			);
 		},
 		delete(name) {
-			response.appendHeader(
-				'Set-Cookie',
-				`${ensureEncodedForJSCookie(
-					name,
-				)}=;Expires=${DATE_IN_THE_PAST.toUTCString()}`,
+			const encodedName = ensureEncodedForJSCookie(name);
+			const setCookieValue = `${encodedName}=;Expires=${DATE_IN_THE_PAST.toUTCString()}`;
+			const existingValues = getExistingSetCookieValues(
+				response.getHeader('Set-Cookie'),
 			);
+
+			// if the value for cookie deletion is already in the Set-Cookie header, we
+			// don't need to add the deletion value again.
+			if (existingValues.includes(setCookieValue)) {
+				return;
+			}
+
+			response.appendHeader('Set-Cookie', setCookieValue);
 		},
 	};
 };
@@ -250,3 +274,8 @@ const serializeSetCookieOptions = (
 // we are not using those chars in the auth keys.
 const ensureEncodedForJSCookie = (name: string): string =>
 	encodeURIComponent(name).replace(/%(2[346B]|5E|60|7C)/g, decodeURIComponent);
+
+const getExistingSetCookieValues = (
+	values: number | string | string[] | undefined,
+): string[] =>
+	values === undefined ? [] : Array.isArray(values) ? values : [String(values)];