fix(MessageStream): handle errors more gracefully in async iterator (#…

…301)

Errors that were thrown in the async iterator of the MessageStream would previously
throw as an unhandled promise rejection.
See: #298

src/lib/MessageStream.ts

@@ -468,13 +468,16 @@ export class MessageStream implements AsyncIterable<MessageStreamEvent> {
 
   [Symbol.asyncIterator](): AsyncIterator<MessageStreamEvent> {
     const pushQueue: MessageStreamEvent[] = [];
-    const readQueue: ((chunk: MessageStreamEvent | undefined) => void)[] = [];
+    const readQueue: {
+      resolve: (chunk: MessageStreamEvent | undefined) => void;
+      reject: (error: unknown) => void;
+    }[] = [];
     let done = false;
 
     this.on('streamEvent', (event) => {
       const reader = readQueue.shift();
       if (reader) {
-        reader(event);
+        reader.resolve(event);
       } else {
         pushQueue.push(event);
       }
@@ -483,7 +486,23 @@ export class MessageStream implements AsyncIterable<MessageStreamEvent> {
     this.on('end', () => {
       done = true;
       for (const reader of readQueue) {
-        reader(undefined);
+        reader.resolve(undefined);
+      }
+      readQueue.length = 0;
+    });
+
+    this.on('abort', (err) => {
+      done = true;
+      for (const reader of readQueue) {
+        reader.reject(err);
+      }
+      readQueue.length = 0;
+    });
+
+    this.on('error', (err) => {
+      done = true;
+      for (const reader of readQueue) {
+        reader.reject(err);
       }
       readQueue.length = 0;
     });
@@ -494,9 +513,9 @@ export class MessageStream implements AsyncIterable<MessageStreamEvent> {
           if (done) {
             return { value: undefined, done: true };
           }
-          return new Promise<MessageStreamEvent | undefined>((resolve) => readQueue.push(resolve)).then(
-            (chunk) => (chunk ? { value: chunk, done: false } : { value: undefined, done: true }),
-          );
+          return new Promise<MessageStreamEvent | undefined>((resolve, reject) =>
+            readQueue.push({ resolve, reject }),
+          ).then((chunk) => (chunk ? { value: chunk, done: false } : { value: undefined, done: true }));
         }
         const chunk = pushQueue.shift()!;
         return { value: chunk, done: false };

tests/api-resources/MessageStream.test.ts

@@ -1,6 +1,6 @@
 import { PassThrough } from 'stream';
 import { Response } from 'node-fetch';
-import Anthropic, { APIUserAbortError } from '@anthropic-ai/sdk';
+import Anthropic, { APIConnectionError, APIUserAbortError } from '@anthropic-ai/sdk';
 import { Message, MessageStreamEvent } from '@anthropic-ai/sdk/resources/messages';
 import { type RequestInfo, type RequestInit } from '@anthropic-ai/sdk/_shims/index';
 
@@ -336,10 +336,62 @@ describe('MessageStream class', () => {
       }
     }
 
-    await stream.done().catch((e) => {
-      expect(e).toBeInstanceOf(APIUserAbortError);
-    });
+    await expect(async () => stream.done()).rejects.toThrow(APIUserAbortError);
 
     expect(stream.aborted).toBe(true);
   });
+
+  it('handles network errors', async () => {
+    const { fetch, handleRequest } = mockFetch();
+
+    const anthropic = new Anthropic({ apiKey: '...', fetch });
+
+    const stream = anthropic.messages.stream(
+      {
+        max_tokens: 1024,
+        model: 'claude-2.1',
+        messages: [{ role: 'user', content: 'Say hello there!' }],
+      },
+      { maxRetries: 0 },
+    );
+
+    handleRequest(async () => {
+      throw new Error('mock request error');
+    });
+
+    async function runStream() {
+      await stream.done();
+    }
+
+    await expect(runStream).rejects.toThrow(APIConnectionError);
+  });
+
+  it('handles network errors on async iterator', async () => {
+    const { fetch, handleRequest } = mockFetch();
+
+    const anthropic = new Anthropic({ apiKey: '...', fetch });
+
+    const stream = anthropic.messages.stream(
+      {
+        max_tokens: 1024,
+        model: 'claude-2.1',
+        messages: [{ role: 'user', content: 'Say hello there!' }],
+      },
+      { maxRetries: 0 },
+    );
+
+    handleRequest(async () => {
+      throw new Error('mock request error');
+    });
+
+    async function runStream() {
+      for await (const event of stream) {
+        if (event.type === 'content_block_delta' && event.delta.text.includes('He')) {
+          break;
+        }
+      }
+    }
+
+    await expect(runStream).rejects.toThrow(APIConnectionError);
+  });
 });