feat(web-api): expose public ts property on ChatStream

[srtaalej]

Summary

This PR adds a public read-only ts getter to ChatStreamer, enabling users to call chat.update as a fallback when the server closes a stream due to undocumented timeouts.

Background

When Slack's server-side timeout kills a stream, both chat.appendStream and chat.stopStream return message_not_in_streaming_state. The message still exists but is stuck as a broken pill in the UI. The only recovery path is chat.update({ ts: ... }), but ts was previously a private field (streamTs).

Changes

• packages/web-api/src/chat-stream.ts: Added ts getter (read-only, returns string | undefined)
• packages/web-api/src/WebClient.test.ts: Added test verifying ts is undefined before flush and set after

code snippet

  import { WebClient } from '@slack/web-api';

  const client = new WebClient(token);

  async function sendStreaming(channel: string, threadTs: string, teamId: string, userId: string, 
  chunks: AsyncIterable<string>) {
    const streamer = client.chatStream({
      channel,
      thread_ts: threadTs,
      recipient_team_id: teamId,
      recipient_user_id: userId,
    });

    let fullText = '';
    let streamAlive = true;

    for await (const chunk of chunks) {
      fullText += chunk;

      if (streamAlive) {
        try {
          await streamer.append({ markdown_text: chunk });
        } catch (error) {
          if (error.data?.error === 'message_not_in_streaming_state') {
            streamAlive = false;
          } else {
            throw error;
          }
        }
      }

      if (!streamAlive) {
        await client.chat.update({ channel, ts: streamer.ts, text: fullText });
      }
    }

    if (streamAlive) {
      await streamer.stop();
    } else {
      await client.chat.update({ channel, ts: streamer.ts, text: fullText });
    }
  }

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[changeset-bot]

🦋 Changeset detected

Latest commit: 3a3a0d6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@slack/web-api	Minor

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.88%. Comparing base (7ad18f2) to head (3a3a0d6).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2611      +/-   ##
==========================================
+ Coverage   88.86%   88.88%   +0.02%     
==========================================
  Files          62       62              
  Lines       10230    10240      +10     
  Branches      450      451       +1     
==========================================
+ Hits         9091     9102      +11     
+ Misses       1117     1116       -1     
  Partials       22       22              

Flag	Coverage Δ
cli-hooks	88.88% <100.00%> (+0.02%)	⬆️
cli-test	88.88% <100.00%> (+0.02%)	⬆️
logger	88.88% <100.00%> (+0.02%)	⬆️
oauth	88.88% <100.00%> (+0.02%)	⬆️
socket-mode	88.88% <100.00%> (+0.02%)	⬆️
web-api	88.88% <100.00%> (+0.02%)	⬆️
webhook	88.88% <100.00%> (+0.02%)	⬆️

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