Keep split GDB/MI result tokens in stdout buffer

src/backend/mi2/mi2.ts

@@ -264,6 +264,11 @@ export class MI2 extends EventEmitter implements IBackend {
     }
 
     private onOutputPartial(line) {
+        // A chunk may end after the digits of an MI result token, before '^done'.
+        // Keep those digits until we have the rest of the record or a newline.
+        if (/^\d+$/.test(line)) {
+            return false;
+        }
         if (couldBeOutput(line)) {
             this.logNoNewLine('stdout', line);
             return true;

test/suite/mi2_stream.test.ts

@@ -0,0 +1,34 @@
+import * as assert from 'assert';
+import { MI2 } from '../../src/backend/mi2/mi2';
+import { MINode } from '../../src/backend/mi_parse';
+
+suite('GDB/MI output stream', () => {
+    test('keeps a result token split from its record marker', () => {
+        const gdb = new MI2('gdb', []);
+        const messages: Array<[string, string]> = [];
+        let response: MINode = undefined;
+        gdb.on('msg', (type: string, message: string) => messages.push([type, message]));
+        (gdb as any).handlers[787] = (result: MINode) => {
+            response = result;
+        };
+
+        (gdb as any).stdout(Buffer.from('787'));
+        assert.strictEqual((gdb as any).buffer, '787');
+        assert.deepStrictEqual(messages, []);
+
+        (gdb as any).stdout(Buffer.from('^done,changelist=[]\n'));
+        assert.strictEqual(response.token, 787);
+        assert.strictEqual(response.resultRecords.resultClass, 'done');
+        assert.strictEqual((gdb as any).handlers[787], undefined);
+        assert.strictEqual((gdb as any).buffer, '');
+    });
+
+    test('still forwards a complete numeric output line', () => {
+        const gdb = new MI2('gdb', []);
+        const messages: Array<[string, string]> = [];
+        gdb.on('msg', (type: string, message: string) => messages.push([type, message]));
+
+        (gdb as any).stdout(Buffer.from('787\n'));
+        assert.deepStrictEqual(messages, [['stdout', '787\n']]);
+    });
+});