Enable using bolt-js without passing bot_id

[seratch]

As of v3.3, developers cannot use bolt-js only with a user token for the following reason. We can revisit ignore self middleware and update the middleware not to rely on given bot_id.

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Hey @~Levelleor! Thanks so much for raising this issue. 🙂

After a little digging, it turns out this is in fact a bug. We've made note of it and will hopefully get a fix out shortly.

In the meantime, to workaround this issue, you can introduce a temporary authorize function that returns both the botId and the userToken, as seen in the example below:

// cached auth.test response
let botAuthTestResult = undefined;

const authorize = async () => {
  if (botAuthTestResult === undefined) {
    // if the cached result does not exist yet
    botAuthTestResult = await app.client.auth.test({token: process.env.SLACK_BOT_TOKEN});
  }
  return {
    // for ignoreSelf middleware compatibility as of bolt-js v3.3
    botId: botAuthTestResult.bot_id,
    // for ignoreSelf middleware compatibility as of bolt-js v3.3
    botUserId: botAuthTestResult.user_id,
    // if the token is a user token, you can use userToken for the key in context
    userToken: process.env.SLACK_USER_TOKEN,
  };
}

const app = new App({
  logLevel: 'debug',
  appToken: process.env.SLACK_APP_TOKEN,
  socketMode: true,
  authorize,
});

Thanks again for bringing this to our attention. Do let us know if the above resolves the problem for the time being!

Originally posted by @misscoded in #869 (comment)

[seratch]

👋 @misscoded I just found that, for v3.7 release https://github.com/slackapi/bolt-js/milestone/11 , you are assigned to #866 and this one. If you want to focus on #866, I think that you can ask other maintainers to work on this task!

[misscoded]

@seratch I actually got around to fixing this one earlier today and have the code sitting locally! I'll open a PR for it tomorrow morning 🙂