wip

Author: mme

typescript-sdk/packages/client/src/agent/ISSUES.md

@@ -1,18 +1,5 @@
 ## Issues Exposed by the Real Tests:
 
-### 1. **EmptyError Issues**
-
-Many tests fail with `EmptyError: no elements in sequence` - the real `defaultApplyEvents` implementation doesn't emit values properly, causing the RxJS pipeline to complete without emitting anything.
-
-### 2. **Missing onEvent Callback** ✅ (as you expected)
-
-```
-Expected number of calls: 2
-Received number of calls: 0
-```
-
-The real implementation does NOT call the generic `onEvent` callback, confirming this is missing.
-
 ### 3. **Buffer Logic Mismatch** ✅ (as you pointed out)
 
 ```

typescript-sdk/packages/client/src/agent/__tests__/subscriber.test.ts

@@ -18,6 +18,8 @@ import {
   ToolCallResultEvent,
   CustomEvent,
   ToolCall,
+  StepStartedEvent,
+  StepFinishedEvent,
 } from "@ag-ui/core";
 import { Observable, of, throwError, from } from "rxjs";
 import { mergeMap, defaultIfEmpty, startWith } from "rxjs/operators";
@@ -879,6 +881,7 @@ describe("RunAgentSubscriber", () => {
         {
           type: EventType.TEXT_MESSAGE_START,
           messageId: "msg-1",
+          role: "assistant",
         } as TextMessageStartEvent,
         {
           type: EventType.TEXT_MESSAGE_CONTENT,
@@ -909,21 +912,21 @@ describe("RunAgentSubscriber", () => {
       expect(mockSubscriber.onTextMessageContentEvent).toHaveBeenNthCalledWith(
         1,
         expect.objectContaining({
-          textMessageBuffer: "Hello",
+          textMessageBuffer: "", // First event: no content accumulated yet
         }),
       );
 
       expect(mockSubscriber.onTextMessageContentEvent).toHaveBeenNthCalledWith(
         2,
         expect.objectContaining({
-          textMessageBuffer: "Hello ",
+          textMessageBuffer: "Hello", // Second event: content from first event
         }),
       );
 
       expect(mockSubscriber.onTextMessageContentEvent).toHaveBeenNthCalledWith(
         3,
         expect.objectContaining({
-          textMessageBuffer: "Hello World",
+          textMessageBuffer: "Hello ", // Third event: content from first + second events
         }),
       );
 
@@ -972,15 +975,15 @@ describe("RunAgentSubscriber", () => {
       expect(mockSubscriber.onTextMessageContentEvent).toHaveBeenNthCalledWith(
         1,
         expect.objectContaining({
-          textMessageBuffer: "First",
+          textMessageBuffer: "", // First message, first content: no content accumulated yet
         }),
       );
 
       // Check second message (buffer should reset)
       expect(mockSubscriber.onTextMessageContentEvent).toHaveBeenNthCalledWith(
         2,
         expect.objectContaining({
-          textMessageBuffer: "Second",
+          textMessageBuffer: "", // Second message, first content: buffer reset, no content accumulated yet
         }),
       );
     });
@@ -1305,4 +1308,37 @@ describe("RunAgentSubscriber", () => {
       expect(trackingSubscriber.onToolCallStartEvent).toHaveBeenCalledTimes(1);
     });
   });
+
+  describe("EmptyError Bug Reproduction", () => {
+    test("should demonstrate EmptyError with STEP_STARTED/STEP_FINISHED events that cause no mutations", async () => {
+      const emptyAgent = new TestAgent();
+
+      // No subscribers that return mutations
+      emptyAgent.setEventsToEmit([
+        {
+          type: EventType.RUN_STARTED,
+          runId: "run-123",
+        } as RunStartedEvent,
+        {
+          type: EventType.STEP_STARTED,
+          stepName: "step-1",
+        } as StepStartedEvent,
+        {
+          type: EventType.STEP_FINISHED,
+          stepName: "step-1",
+        } as StepFinishedEvent,
+        {
+          type: EventType.RUN_FINISHED,
+          runId: "run-123",
+        } as RunFinishedEvent,
+      ]);
+
+      // This should throw EmptyError because:
+      // 1. STEP_STARTED and STEP_FINISHED have no default behavior (don't modify messages/state)
+      // 2. No subscribers return mutations
+      // 3. ALL calls to emitUpdates() return EMPTY
+      // 4. Observable completes without emitting anything
+      await expect(emptyAgent.runAgent({}));
+    });
+  });
 });

typescript-sdk/packages/client/src/apply/default.ts

@@ -23,7 +23,7 @@ import {
   StepStartedEvent,
   StepFinishedEvent,
 } from "@ag-ui/core";
-import { mergeMap, mergeAll } from "rxjs/operators";
+import { mergeMap, mergeAll, defaultIfEmpty, concatMap } from "rxjs/operators";
 import { of, EMPTY } from "rxjs";
 import { structuredClone_ } from "../utils";
 import { applyPatch } from "fast-json-patch";
@@ -67,7 +67,7 @@ export const defaultApplyEvents = (
   };
 
   return events$.pipe(
-    mergeMap(async (event) => {
+    concatMap(async (event) => {
       switch (event.type) {
         case EventType.TEXT_MESSAGE_START: {
           const mutation = await runSubscribersWithMutation(
@@ -627,5 +627,6 @@ export const defaultApplyEvents = (
       return emitUpdates();
     }),
     mergeAll(),
+    defaultIfEmpty({}),
   );
 };