Events get stuck when no conversation context is found

[aoberoi]

Description

In the conversation context middleware, which is included by default (and only turned off when the convoStore: false option is used for App initialization), events which have no channel context found result in the propagation ending. This can be seen by inspecting the middleware function itself, and noticing that in the else case, next() is never called.

https://github.com/slackapi/bolt/blob/7596366d6e6fc763b6e855f6259d19056605e4cf/src/conversation-store.ts#L54-L76

This is a bug. The expected behavior is that events which have no conversation context should continue to be processed by the next middleware.

Notably, the middleware is working correctly for events which do have a conversation context, but no existing conversation data was found for that conversationId. In those cases, an updateConversation() function is added to the context, which would initialize the conversation data.

Requirements (place an x in each of the [ ])

• I've read and understood the Contributing guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've searched for any related issues and avoided creating a duplicate issue.

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Bug Report

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Reproducible in:

package version: 1.0.1

node version: all

OS version(s): all

Steps to reproduce:

1. Initialize an App with default options
2. Subscribe to an event that isn't related to a channel, and add a listener for that event. For example, team_join.
3. Attempt to trigger the event.

Expected result:

Listener should be triggered

Actual result:

Listener is not triggered