v1 stdio buffer limit (#2239)

test/shared/stdio.test.ts

@@ -1,5 +1,5 @@
 import { JSONRPCMessage } from '../../src/types.js';
-import { ReadBuffer } from '../../src/shared/stdio.js';
+import { STDIO_DEFAULT_MAX_BUFFER_SIZE, ReadBuffer } from '../../src/shared/stdio.js';
 
 const testMessage: JSONRPCMessage = {
     jsonrpc: '2.0',
@@ -33,3 +33,46 @@ test('should be reusable after clearing', () => {
     readBuffer.append(Buffer.from('\n'));
     expect(readBuffer.readMessage()).toEqual(testMessage);
 });
+
+describe('buffer size limit', () => {
+    test('should throw when buffer exceeds default max size', () => {
+        const readBuffer = new ReadBuffer();
+        const chunkSize = 1024 * 1024; // 1 MB
+        const chunk = Buffer.alloc(chunkSize);
+        const chunksToFill = Math.floor(STDIO_DEFAULT_MAX_BUFFER_SIZE / chunkSize);
+        for (let i = 0; i < chunksToFill; i++) {
+            readBuffer.append(chunk);
+        }
+        expect(() => readBuffer.append(chunk)).toThrow(/ReadBuffer exceeded maximum size/);
+    });
+
+    test('should throw when buffer exceeds custom max size', () => {
+        const readBuffer = new ReadBuffer({ maxBufferSize: 100 });
+        readBuffer.append(Buffer.alloc(50));
+        expect(() => readBuffer.append(Buffer.alloc(51))).toThrow(/ReadBuffer exceeded maximum size/);
+    });
+
+    test('should clear buffer before throwing on overflow', () => {
+        const readBuffer = new ReadBuffer({ maxBufferSize: 100 });
+        readBuffer.append(Buffer.alloc(50));
+        expect(() => readBuffer.append(Buffer.alloc(51))).toThrow();
+
+        // Buffer should be cleared — can append again
+        readBuffer.append(Buffer.alloc(50));
+        // And read messages normally
+        expect(readBuffer.readMessage()).toBeNull();
+    });
+
+    test('should allow appending up to exactly the max size', () => {
+        const readBuffer = new ReadBuffer({ maxBufferSize: 100 });
+        // Should not throw — exactly at limit
+        expect(() => readBuffer.append(Buffer.alloc(100))).not.toThrow();
+    });
+
+    test('should work with no options (backwards compatible)', () => {
+        const readBuffer = new ReadBuffer();
+        // Small append should always work
+        readBuffer.append(Buffer.from(JSON.stringify({ jsonrpc: '2.0', method: 'ping' }) + '\n'));
+        expect(readBuffer.readMessage()).not.toBeNull();
+    });
+});