Clarify about chat.update only work with channels and not DMs

[nahuelhds]

Hi! Was trying the example for updating a message and two things that happened.

The action succeed but no update happen. First of all, the action itself was failing, actually with message_not_found error but the action reports success anyway.

See the following image

You can see the last three lines

##[debug]Set output response = {"ok":false,"error":"message_not_found","response_metadata":{"scopes":["incoming-webhook","chat:write"],"acceptedScopes":["chat:write"]}}
##[debug]Set output time = 1738447171
##[debug]Finishing: Update the original message with success

Ok = False, but "Update the original message with sucess" (?

Doing some more research, I learned that my issue was that I was trying to post to a private message and this only works with channels. I'd be nice to warn about this in the docs :)

[zimeg]

Hey @nahuelhds 👋 Thanks for sharing the details of your investigation into this! 🔍

The failure mode of this action defaults to silent API errors which can be toggled on to cause errors from the Slack API to exit the step with an error:

  - uses: slackapi/slack-github-action@v2.0.0
    with:
+     errors: true

This can certainly create confusing cases like what you're finding, but this default was picked to avoid breaking an entire CI pipeline if, perhaps, posting a "completion" message was to fail as the very last step due to a server outage or similar.

Updating a message using a user ID with chat.update also isn't supported, as you've noted. I agree this isn't a nice edge to discover... However, the conversation ID of the DM can be used here instead! This will start with a "D":

  - uses: slackapi/slack-github-action@v2.0.0
    with:
      method: chat.update
      token: ${{ secrets.SLACK_BOT_TOKEN }}
      payload: |
+       channel: D0123456789
        ts: "${{ steps.launch_sequence.outputs.ts }}"
        text: "Deployment finished! :rocket:"

Setting errors to true might be helpful when debugging, but I'm hoping the updated conversation ID helps with these message updates - please let me know in whichever case or if other questions arise 🙏 ✨

I'll share a note about the allowed conversation types with our documentation team since I'm hoping the Slack API reference can serve as a source of truth for accepted arguments 📚

[zimeg]

📚 ✨ Meant to share this update sooner, but the API docs now make a note of accepted channel values for chat.update:

Channel containing the message to be updated. For direct messages, ensure that this value is a DM ID (starts with D) instead of a User ID (starts with either U or W).

Since these error cases have a known cause, and documentation is updated with these findings, I'll go ahead and close this issue! Please do feel free to follow up with other questions or confusions you might find with this action whenever 🙏