socket-mode: Type event payloads

[slifty]

I'm using @slack/socket-mode in a TypeScript project and would love to be able to benefit from type definitions when defining event handlers -- e.g. when I invoke something along the lines of

socketModeClient.on(
  'reaction_added',
  async (event) => {
    ...
  }
);

I'd like event to not be of the any type but instead to reflect the expected type for the event in question.

It looks like there are libraries that might support this, for your consideration.

Packages:

Select all that apply:

• [ ] @slack/web-api
• [ ] @slack/rtm-api
• [ ] @slack/webhooks
• [ ] @slack/oauth
• [x] @slack/socket-mode
• [ ] @slack/types
• [ ] I don't know

Requirements

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you are agreeing to those rules.

[filmaj]

I agree this would be a fantastic enhancement. The issue is that perfect typing for Slack payload events is challenging, as the payloads can be quite contextual. For example, depending on the Slack workspace type (enterprise vs. standalone), the payloads might differ. Additionally, some payloads may or may not contain properties depending on the context, for example a block_actions payload contains a container property, which might be a View object or might be a containing message.

That said, at least some baseline form of event typing should be doable. I will leave this as an enhancement issue open but can make no promises on a delivery timeline.

[filmaj]

I suppose this would technically be a breaking change, yes? Going from any to something more specific may possibly break existing apps, so this would be a major version change - but would be a great one!

This issue comment in the EventEmitter3 package that powers socket-mode has some great examples of using its generics support to provide nice type completion. I think this would be worthwhile doing!

First, though, what needs to happen:

• https://github.com/slackapi/node-slack-sdk/issues/1395 for simply adding event payload types to the @slack/types repo.
• https://github.com/slackapi/node-slack-sdk/issues/1904 for breaking these types in a new major version of @slack/types

Once these are in place, we can consume the new @slack/types@3.0+ package and leverage EventEmitter3 generics to provide a much better experience for socket-mode consumers.