`return` in a generator function crashes after iterating an `@azure/core-sse` `EventMessageStream` to the end

[jaked]

• Package Name: @azure/core-sse
• Package Version: 2.1.2
• Operating system: MacOS
• [x] nodejs
  • version: 20.10.0
• [ ] browser
  • name/version:
• [ ] typescript
  • version:
• Is the bug related to documentation in
  • [ ] README.md
  • [ ] source code documentation
  • [ ] SDK API docs on https://learn.microsoft.com

Describe the bug Returning from an iteration over an EventMessageStream crashes if the entire stream has already been consumed.

To Reproduce Steps to reproduce the behavior:

1. obtain a stream with createSseStream (e.g. from an @azure-rest/ai-inference response body)
2. iterate the stream in a generator function (with for await (const event of stream))
3. return from the iterator when complete (e.g. with if (event.data === "[DONE]") return)
4. observe exception:

   TypeError: Cannot read properties of null (reading 'end')
   at Object.cancel (file:///Users/jaked/repos/githubnext/vitale/node_modules/.pnpm/@azure+core-sse@2.1.2/node_modules/@azure/core-sse/dist/esm/utils.js:54:31)
   at readableStreamDefaultControllerCancelSteps (node:internal/webstreams/readablestream:2383:39)
   at ReadableStreamDefaultController.[kCancel] (node:internal/webstreams/readablestream:1079:12)
   at ensureIsPromise (node:internal/webstreams/util:185:19)
   at readableStreamCancel (node:internal/webstreams/readablestream:1984:5)
   at readableStreamReaderGenericCancel (node:internal/webstreams/readablestream:2124:10)
   at returnSteps (node:internal/webstreams/readablestream:524:24)
   at Object.return (node:internal/webstreams/readablestream:568:11)
   at main (/Users/jaked/repos/githubnext/vitale/packages/examples/azure-ai.vnb-cellId=fUdPs5uLJxWHELOq-T1-8.tsx:40:3)
   at main.next (<anonymous>)

Expected behavior Iteration completes normally without exception.

Screenshots If applicable, add screenshots to help explain your problem.

Additional context The exception is coming from the cancel function in @azure/core-sse/utils.js, which calls stream.socket.end() when an EventMessageStream iteration returns in a generator function (since https://github.com/Azure/azure-sdk-for-js/pull/28111). But Node sets stream.socket to null when the underlying message has been consumed (I think since https://github.com/nodejs/node/pull/38505 / https://github.com/nodejs/undici/pull/834), so the call fails.

Replacing stream.socket.end() with stream.socket?.end() fixes the issue for me.

[github-actions[bot]]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @xgithubtriage.

[deyaaeldeen]

Hi @jaked, thanks for opening this report and apologies for the delay. I agree with your analysis and proposed remedy and I opened https://github.com/Azure/azure-sdk-for-js/pull/30707. I'll let you know once we make a release. Again, thanks for your patience!

[deyaaeldeen]

@jaked @azure/core-sse@2.1.3 has been released! Please let us know if you have any other questions!

[github-actions[bot]]

Hi @jaked. Thank you for opening this issue and giving us the opportunity to assist. We believe that this has been addressed. If you feel that further discussion is needed, please add a comment with the text "/unresolve" to remove the "issue-addressed" label and continue the conversation.

[github-actions[bot]]

Hi @jaked, since you haven’t asked that we /unresolve the issue, we’ll close this out. If you believe further discussion is needed, please add a comment /unresolve to reopen the issue.

[jaked]

thanks! I haven't had a chance to verify the fix but the change looks good to me.