Cannot post message to DM or private group

Description

When I call app.client.chat.postMessage with the channel id of a direct message or private group, I get the error channel_not_found. I’m confused because my bot is able to post in channels fine. I’ve read through the api for postMessage multiple times but still don’t understand what my problem is. Thanks!

What type of issue is this? (place an x in one of the [ ])

• bug
• enhancement (feature request)
• question
• documentation related
• testing related
• discussion

[aoberoi]

Hey folks I think I can provide some help here.

In the case of slash commands, neither a bot token nor a user token are necessary. From a security point of view, a user invoking a slash command is considered an implicit temporary grant for the app to post a message back to that conversation.

So if your app just wants to send a message to the conversation where the slash command was invoked, there’s no reason to try and get app.client.chat.postMessage() to work with the right token. Instead, use the respond() function, which is passed as an argument to your listener function. The respond() function have be used up to 5 times within 30 minutes after the slash command was invoked. Under the hood, it uses the response_url, which is described here: https://api.slack.com/interactivity/handling#message_responses. It’s also alluded to in the Bolt for JS docs , but maybe a complete example would be more helpful:

app.command('/demo', async ({ command, ack, respond }) => {
  
  // Let the user know immediately that their command was received
  await ack('One moment please...');
  

  // Do some stuff that may take a while (possibly more than 3 seconds)
  const result = await doSomeStuff(command.text);
  await respond({
    // Replace the previous message to clean up the history
    replace_original: true,
    text: `The result is ${result}`,
  });
});

For completeness, I should probably also mention that if you can come up with a response immediately (without calling some other async operation) then you should just use that as the argument for await ack(), as I’ve done above with “One moment please…”.

[jacklein]

@securisec unfortunately it seems that this action isn’t possible anymore with the new apps. with a legacy slack app this was possible, but as of a few months ago you have to use version 2 of slack’s oauth. it’s sort of unbelievable that the new version of slack apps leave this function out :–(