say type incorrectly inferred as never when using SlackEventMiddlewareArgs<'pin_added'>

[wickerpopstar]

Description

The SlackEventMiddlewareArgs type contains a say property that is set to type SayFn if the event contains a channel property or a item.channel property. The PinAddedEvent type does have an item.channel property, however the WhenEventHasChannelContext returns never nonetheless.

For example, the following code causes the TS error

error TS2349: This expression is not callable. Type 'never' has no call signatures.

but while running the code, you can clearly see that say correctly exists as a function:

async function handlePinAdded(
  { say }
    : SlackEventMiddlewareArgs<'pin_added'>): Promise<void> {
  await say("message");
}

I noticed that the PinAddedEvent.item property is a Record<string, unknown>, so it may be that the WhenEventHasChannelContext type function always returns never due to the unknown, but I'm not entirely clear on how that field populates. The ReactionAddedEvent also has this problem, likely because its item property is a union type of ReactionMessageItem | ReactionFileItem | ReactionFileCommentItem and only ReactionMessageItem has a channel field.

As a positive case, using SlackEventMiddlewareArgs<'message'> works correctly and TS infers say to be a SayFn.

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

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

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: 3.11.x

node version: 14.x

OS version(s): macOS Big Sur 11.6.6

Steps to reproduce:

1. Register an event handler on your app (for example, app.event('pin_added', handlePinAdded);
2. Inside the function, attempt to infer the type of the say property on the event.
3. Call say('some message);' inside the event handler.

Expected result:

TS correctly infers the type of say to be SayFn and transpiles without errors.

Actual result:

TS incorrectly infers the type of say to be never.

Attachments:

[srajiang]

Thanks for reporting this @wickerpopstar and for providing some repro steps. Let me take a look see and see if we can introduce a fix.

[srajiang]

Hi @wickerpopstar! Can you try adding AllMiddlewareArgs to the type definition and see if that corrects the type resolution issue? Here's a related issue

[wickerpopstar]

@srajiang Thanks for the suggestion! I actually do have that in my real code, but I removed it to keep the example simple. Unfortunately, it doesn't resolve the issue as the AllMiddlewareArgs interface only contains context, logger, client, and next in its definition.

[seratch]

@wickerpopstar Thanks for reporting this issue. I found that this is a bug that affects pin_added and pin_removed event use cases. Here is a fix for it: #1473