Message Attachments missing when posting message to Slack App Home channel

Question

I've built a Workspace App for Slack, which now comes with a channel (under the Apps header), where a user can send messages to the app itself. This triggers a message.app_home event, that my backend receives. I want to respond to that message, using chat.postMessage , but only the message text appears in the response. None of the attachments I send along appear in the channel. Returning this structure as part of a JSON response to a Slash Command request works correctly.

Here are the attachments structure I sending along:

(
    {
        "title": "Create a space, optionally setting its name and adding other users",
        "text": "`/luffa create [space name] [teammates]`\nExample: `/luffa create Marketing Campaign 2018 @john @kate`",
        "color": SLACK_COLOR,
    },
    {
        "title": "Start a new meeting, optionally strating it in the space matching the provided name",
        "text": "`/luffa start [space name]`\nExample: `/luffa start Marketing Campaign 2018`",
        "color": SLACK_COLOR,
    },
    {
        "title": "Search Luffa",
        "text": "`/luffa search [query]`\nExample: `/luffa search interviews before:Yesterday `",
        "color": SLACK_COLOR,
    },
    {
        "text": "There is more help available in our Help Center: https://help.okluffa.com/",
    },
)

I am using the slackclient Python library to wrap my calls to the Slack API.

There is no error message returned and the structure seems to be correct based on the documentation . Is there something missing there?

Answer 1

Something small to check - try removing the extra commas on each last value in your attachments structure, as those are causing validation errors when plugged into the Slack message tester here :

Answer 2

The issue turned out that the data structure I was passing to slackclient 1.2.1 was a tuple of objects. The library will only serialize as JSON list or dict objects. (See slackrequest.py , line 94, if isinstance(v, (list, dict)): ). Passing a tuple, or any other iterable for that matter, will not be serialized correctly and the Slack API will disregard the attachments. That was not an issue with a JSON response to a request, since Python's JSON serializer converts all iterables to a JSON array.

I solved the issue by passing in a list to the slackclient method.