@W-22169002: Use composition over inheritance for Server class

package.json

@@ -1,7 +1,7 @@
 {
   "name": "@tableau/mcp-server",
   "description": "Helping agents see and understand data.",
-  "version": "1.18.7",
+  "version": "1.18.8",
   "repository": {
     "type": "git",
     "url": "git+https://github.com/tableau/tableau-mcp.git"

src/index.ts

@@ -42,7 +42,7 @@ async function startServer(): Promise<void> {
       server.registerRequestHandlers();
 
       const transport = new StdioServerTransport();
-      await server.connect(transport);
+      await server.mcpServer.connect(transport);
 
       setNotificationLevel(server, logLevel);
       notifier.info(server, `${server.name} v${server.version} running on stdio`);

src/logging/notification.test.ts

@@ -44,7 +44,7 @@ describe('notification', () => {
       const server = new Server();
       setNotificationLevel(server, 'debug', { silent: true });
       setNotificationLevel(server, 'debug', { silent: true });
-      expect(server.server.notification).not.toHaveBeenCalled();
+      expect(server.mcpServer.server.notification).not.toHaveBeenCalled();
     });
   });
 
@@ -120,7 +120,7 @@ describe('notification', () => {
 
       await notifier.info(server, 'test message', { notifier: 'test-logger' });
 
-      expect(server.server.notification).toHaveBeenCalledWith(
+      expect(server.mcpServer.server.notification).toHaveBeenCalledWith(
         {
           method: 'notifications/message',
           params: {
@@ -141,7 +141,7 @@ describe('notification', () => {
 
       await notifier.debug(server, 'test message', { notifier: 'test-logger' });
 
-      expect(server.server.notification).not.toHaveBeenCalled();
+      expect(server.mcpServer.server.notification).not.toHaveBeenCalled();
     });
 
     it('should use server name as default logger', async () => {
@@ -150,7 +150,7 @@ describe('notification', () => {
 
       await notifier.info(server, 'test message');
 
-      expect(server.server.notification).toHaveBeenCalledWith(
+      expect(server.mcpServer.server.notification).toHaveBeenCalledWith(
         {
           method: 'notifications/message',
           params: {
@@ -176,7 +176,7 @@ describe('notification', () => {
 
       await notifier.info(server, logMessage, { notifier: 'test-logger' });
 
-      expect(server.server.notification).toHaveBeenCalledWith(
+      expect(server.mcpServer.server.notification).toHaveBeenCalledWith(
         {
           method: 'notifications/message',
           params: {

src/logging/notification.ts

@@ -105,7 +105,7 @@ function getSendNotificationMessageFn(level: LoggingLevel) {
 
     // server.sendNotification doesn't provide a way to provide the relatedRequestId
     // so we're using server.notification directly.
-    return server.server.notification(
+    return server.mcpServer.server.notification(
       {
         method: 'notifications/message',
         params: {

src/server.test.ts

@@ -30,7 +30,7 @@ describe('server', () => {
     const disabledFlags = await Promise.all(allTools.map((tool) => Provider.from(tool.disabled)));
     const tools = allTools.filter((_, i) => !disabledFlags[i]);
     for (const tool of tools) {
-      expect(server.registerTool).toHaveBeenCalledWith(
+      expect(server.mcpServer.registerTool).toHaveBeenCalledWith(
         tool.name,
         {
           description: await Provider.from(tool.description),
@@ -54,7 +54,7 @@ describe('server', () => {
     );
     const disabledTools = allDisabledTools.filter((_, i) => disabledToolFlags[i]);
     for (const tool of disabledTools) {
-      expect(server.registerTool).not.toHaveBeenCalledWith(
+      expect(server.mcpServer.registerTool).not.toHaveBeenCalledWith(
         tool.name,
         expect.anything(),
         expect.anything(),
@@ -68,7 +68,7 @@ describe('server', () => {
     await server.registerTools();
 
     const tool = getQueryDatasourceTool(server, testProductVersion);
-    expect(server.registerTool).toHaveBeenCalledWith(
+    expect(server.mcpServer.registerTool).toHaveBeenCalledWith(
       tool.name,
       {
         description: await Provider.from(tool.description),
@@ -90,13 +90,13 @@ describe('server', () => {
     );
     for (const [i, tool] of tools.entries()) {
       if (tool.name === 'query-datasource' || excludeDisabledFlags[i]) {
-        expect(server.registerTool).not.toHaveBeenCalledWith(
+        expect(server.mcpServer.registerTool).not.toHaveBeenCalledWith(
           tool.name,
           expect.anything(),
           expect.anything(),
         );
       } else {
-        expect(server.registerTool).toHaveBeenCalledWith(
+        expect(server.mcpServer.registerTool).toHaveBeenCalledWith(
           tool.name,
           {
             description: await Provider.from(tool.description),
@@ -128,15 +128,15 @@ describe('server', () => {
 
   it('should register request handlers', async () => {
     const server = getServer();
-    server.server.setRequestHandler = vi.fn();
+    server.mcpServer.server.setRequestHandler = vi.fn();
     server.registerRequestHandlers();
 
-    expect(server.server.setRequestHandler).toHaveBeenCalled();
+    expect(server.mcpServer.server.setRequestHandler).toHaveBeenCalled();
   });
 });
 
 function getServer(): InstanceType<typeof Server> {
   const server = new Server();
-  server.registerTool = vi.fn();
+  server.mcpServer.registerTool = vi.fn();
   return server;
 }

src/server.ts

@@ -26,7 +26,8 @@ export const userAgent = `${serverName}/${serverVersion}`;
 
 export type ClientInfo = InitializeRequest['params']['clientInfo'];
 
-export class Server extends McpServer {
+export class Server {
+  readonly mcpServer: McpServer;
   readonly name: string;
   readonly version: string;
 
@@ -41,22 +42,24 @@ export class Server extends McpServer {
   private readonly _clientInfo: ClientInfo | undefined;
 
   get clientInfo(): ClientInfo | undefined {
-    return this._clientInfo ?? this.server.getClientVersion();
+    return this._clientInfo ?? this.mcpServer.server.getClientVersion();
   }
 
-  constructor({ clientInfo }: { clientInfo?: ClientInfo } = {}) {
-    super(
-      {
-        name: serverName,
-        version: serverVersion,
-      },
-      {
-        capabilities: {
-          logging: {},
-          tools: {},
+  constructor({ clientInfo, mcpServer }: { clientInfo?: ClientInfo; mcpServer?: McpServer } = {}) {
+    this.mcpServer =
+      mcpServer ??
+      new McpServer(
+        {
+          name: serverName,
+          version: serverVersion,
         },
-      },
-    );
+        {
+          capabilities: {
+            logging: {},
+            tools: {},
+          },
+        },
+      );
 
     this.name = serverName;
     this.version = serverVersion;
@@ -114,7 +117,7 @@ export class Server extends McpServer {
         return tableauToolCallback(args, tableauRequestHandlerExtra);
       };
 
-      this.registerTool(
+      this.mcpServer.registerTool(
         name,
         {
           description: await Provider.from(description),
@@ -127,7 +130,7 @@ export class Server extends McpServer {
   };
 
   registerRequestHandlers = (): void => {
-    this.server.setRequestHandler(SetLevelRequestSchema, async (request) => {
+    this.mcpServer.server.setRequestHandler(SetLevelRequestSchema, async (request) => {
       setNotificationLevel(this, request.params.level);
       return {};
     });

src/server/express.ts

@@ -127,7 +127,7 @@ export async function startExpressServer({
 
         res.on('close', () => {
           transport.close();
-          server.close();
+          server.mcpServer.close();
         });
 
         await connect(server, transport, logLevel, getTableauAuthInfo(req.auth));
@@ -183,7 +183,7 @@ async function connect(
   await server.registerTools(authInfo);
   server.registerRequestHandlers();
 
-  await server.connect(transport);
+  await server.mcpServer.connect(transport);
   setNotificationLevel(server, logLevel);
 }
 

src/testSetup.ts

@@ -6,8 +6,10 @@ vi.mock('./server.js', async (importOriginal) => ({
   ...(await importOriginal()),
   Server: vi.fn().mockImplementation(() => ({
     name: 'test-server',
-    server: {
-      notification: vi.fn(),
+    mcpServer: {
+      server: {
+        notification: vi.fn(),
+      },
     },
   })),
 }));

src/tools/pulse/listMetricSubscriptions/listPulseMetricSubscriptions.test.ts

@@ -186,6 +186,6 @@ async function getToolResult(): Promise<CallToolResult> {
 
 function getServer(): InstanceType<typeof Server> {
   const server = new Server();
-  server.tool = vi.fn();
+  server.mcpServer.registerTool = vi.fn();
   return server;
 }