fix hanging stdio servers (#1200)

Co-authored-by: Johnny Santos <johnnyadsantos@gmail.com>
Co-authored-by: TomasRup <tomasr@wix.com>

src/integration-tests/processCleanup.test.ts

@@ -0,0 +1,113 @@
+import path from 'node:path';
+import { Readable, Writable } from 'node:stream';
+import { Client } from '../client/index.js';
+import { StdioClientTransport } from '../client/stdio.js';
+import { Server } from '../server/index.js';
+import { StdioServerTransport } from '../server/stdio.js';
+import { LoggingMessageNotificationSchema } from '../types.js';
+
+const FIXTURES_DIR = path.resolve(__dirname, '../__fixtures__');
+
+describe('Process cleanup', () => {
+    vi.setConfig({ testTimeout: 5000 }); // 5 second timeout
+
+    it('server should exit cleanly after closing transport', async () => {
+        const server = new Server(
+            {
+                name: 'test-server',
+                version: '1.0.0'
+            },
+            {
+                capabilities: {}
+            }
+        );
+
+        const mockReadable = new Readable({
+                read() {
+                    this.push(null); // signal EOF
+                }
+            }),
+            mockWritable = new Writable({
+                write(chunk, encoding, callback) {
+                    callback();
+                }
+            });
+
+        // Attach mock streams to process for the server transport
+        const transport = new StdioServerTransport(mockReadable, mockWritable);
+        await server.connect(transport);
+
+        // Close the transport
+        await transport.close();
+
+        // ensure a proper disposal mock streams
+        mockReadable.destroy();
+        mockWritable.destroy();
+
+        // If we reach here without hanging, the test passes
+        // The test runner will fail if the process hangs
+        expect(true).toBe(true);
+    });
+
+    it('onclose should be called exactly once', async () => {
+        const client = new Client({
+            name: 'test-client',
+            version: '1.0.0'
+        });
+
+        const transport = new StdioClientTransport({
+            command: 'node',
+            args: ['--import', 'tsx', 'testServer.ts'],
+            cwd: FIXTURES_DIR
+        });
+
+        await client.connect(transport);
+
+        let onCloseWasCalled = 0;
+        client.onclose = () => {
+            onCloseWasCalled++;
+        };
+
+        await client.close();
+
+        // A short delay to allow the close event to propagate
+        await new Promise(resolve => setTimeout(resolve, 50));
+
+        expect(onCloseWasCalled).toBe(1);
+    });
+
+    it('should exit cleanly for a server that hangs', async () => {
+        const client = new Client({
+            name: 'test-client',
+            version: '1.0.0'
+        });
+
+        const transport = new StdioClientTransport({
+            command: 'node',
+            args: ['--import', 'tsx', 'serverThatHangs.ts'],
+            cwd: FIXTURES_DIR
+        });
+
+        await client.connect(transport);
+        await client.setLoggingLevel('debug');
+        client.setNotificationHandler(LoggingMessageNotificationSchema, notification => {
+            console.debug('server log: ' + notification.params.data);
+        });
+        const serverPid = transport.pid!;
+
+        await client.close();
+
+        // A short delay to allow the close event to propagate
+        await new Promise(resolve => setTimeout(resolve, 50));
+
+        try {
+            process.kill(serverPid, 9);
+            throw new Error('Expected server to be dead but it is alive');
+        } catch (err: unknown) {
+            // 'ESRCH' the process doesn't exist
+            if (err && typeof err === 'object' && 'code' in err && err.code === 'ESRCH') {
+                // success
+            } else throw err;
+        }
+    });
+});