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Migrating to V4

This guide will walk you through the process of updating your app from using @slack/bolt@3.x to @slack/bolt@4.x. There may be a few changes you'll need to make depending on which features you use, but for most apps, these changes can be applied in a few minutes. Some apps may need no changes at all.

🚨 Breaking Changes​

✨ Other Changes​

⬆️ Minimum Node version​

@slack/bolt@4.x requires a minimum Node version of 18 and minimum npm version of 8.6.0 .

🚥 Changes to middleware argument types​

This change primarily applies to TypeScript users.

Many middleware argument types, for example the SlackEventMiddlewareArgs type, previously used a conditional to sometimes define particular additional helper utilities on the middleware arguments. For example, the say utility, or tacking on a convenience message property for message-event-related payloads. This was problematic: when the payload was not of a type that required the extra utility, these properties would be required to exist on the middleware arguments but have a type of undefined. Those of us trying to build generic middleware utilities would have to deal with TypeScript compilation errors and needing to liberally type-cast to avoid these conditional mismatches with undefined.

Instead, these MiddlewareArgs types now conditionally create a type intersection when appropriate in order to provide this conditional-utility-extension mechanism. That looks something like:

type SomeMiddlewareArgs<EventType extends string = string> = {
  // some type in here
} & (EventType extends 'message'
  // If this is a message event, add a `message` property
  ? { message: EventFromType<EventType> }
  : unknown
)

With the above, now when a message payload is wrapped in middleware arguments, it will contain an appropriate message property, whereas a non-message payload will be intersected with unknown - effectively a type "noop." No more e.g. say: undefined or message: undefined to deal with!

🌐 @slack/web-api v7 upgrade​

All bolt handlers are provided a convenience client argument that developers can use to make API requests to Slack's public HTTP APIs. This client is powered by the @slack/web-api package. In bolt v4, web-api has been upgraded from v6 to v7.

More APIs! Better argument type safety! And a whole slew of other changes, too. Many of these changes won't affect JavaScript application builders, but if you are building a bolt app using TypeScript, you may see some compilation issues. Head over to the @slack/web-api v6 -> v7 migration guide to get the details on what changed and how to migrate to v7.

🔌 @slack/socket-mode v2 upgrade​

While the breaking changes from this upgrade should be shielded from most bolt-js users, if you are using the SocketModeReceiver or setting socketMode: true and attach custom code to how the SocketModeReceiver operates, we suggest you read through the @slack/socket-mode v1 -> v2 migration guide, just in case.

🚅 express v5 upgrade​

For those building bolt-js apps using the ExpressReceiver, the packaged express version has been upgraded to v5. Best to check the list of breaking changes in express v5 and keep tabs on express#5944, which tracks the creation of an express v4 -> v5 migration guide.

🍽️ @slack/types exported as a named types export​

We are slowly moving more core Slack domain object types and interfaces into the utility package @slack/types. For example, recently we shuffled Slack Events API payloads from bolt-js over to @slack/types. Similar moves will continue as we improve bolt-js. Ideally, we'd like for everyone - ourselves as Slack employees but of course you as well, dear developer - to leverage these types when modeling Slack domain objects.

Anyways, previously we simply export * from '@slack/types'; in bolt-js. We've tweaked this somewhat, it is now: export * as types from '@slack/types';. So if you are using @slack/types when packaged within bolt-js, please update your references to something like:

import { App, type types } from '@slack/bolt';

// Now you can get references to e.g. `types.BotMessageEvent`

🧘 SocketModeFunctions class disassembled​

If you previously imported the SocketModeFunctions class, you likely only did so to get a reference to the single static method available on this class: defaultProcessEventErrorHandler. Instead, you can now directly import the named defaultProcessEventErrorHandler export instead:

// before:
import { SocketModeFunctions } from '@slack/bolt';
// you probably did something with:
SocketModeFunctions.defaultProcessEventErrorHandler

// now:
import { defaultProcessEventHandler } from '@slack/bolt';

🏭 Built-in middleware changes​

Two built-in middlewares, ignoreSelf and directMention, previously needed to be invoked as a function in order to return a middleware. These two built-in middlewares were not parameterized in the sense that they should just be used directly; as a result, you no longer should invoke them and instead pass them directly.

As an example, previously you may have leveraged directMention like this:

app.message(directMention(), async (args) => {
  // my handler here
});

Instead, you should now use it like so:

app.message(directMention, async (args) => {
  // my handler here
});

🌩️ AwsEvent interface changes​

For users of the AwsLambdaReceiver and TypeScript, we previously modeled, rather simplistically, the AWS event payloads: liberal use of any and in certain cases, incorrect property types altogether. We've now improved these to be more accurate and to take into account the two versions of API Gateway payloads that AWS supports (v1 and v2). Details for these changes are available in #2277.

As for userland changes that may be required, this depends on your use of the AwsEvent interface. The major change here is that it is a union type of V1 and V2 payload structures. Check out the source code and changes in #2277 for details on what each payload version structure looks like and how to adapt your application code to account for these differences. Most likely, your code will need to test for the existence of certain properties in order for TypeScript to narrow down to the appropriate payload version. For example, one change bolt-js had to employ in its code as a result of this more correct typing is the following:

// the variable `awsEvent` is of type `AwsEvent`
let path: string;
if ('path' in awsEvent) {
  // This is a v1 payload, so `awsEvent.path` exists and points to the request URL path.
  path = awsEvent.path;
} else {
  // This is a v2 payload, so `awsEvent.rawPath` exists and points to the request URL path.
  path = awsEvent.rawPath;
}
this.logger.info(`No request handler matched the request: ${path}`);

🧹 Removed deprecations​

  • The deprecated type KnownKeys was removed. Admittedly, it wasn't very useful: export type KnownKeys<_T> = never;
  • The deprecated types VerifyOptions and OptionsRequest were removed.
  • The deprecated methods extractRetryNum, extractRetryReason, defaultRenderHtmlForInstallPath, renderHtmlForInstallPath and verify were removed.

🚳 Steps From Apps related deprecations​

A variety of methods, constants and types related to Steps From Apps were deprecated and will be removed in bolt-js v5.

📦 @slack/web-api exported as webApi​

To help application developers keep versions of various @slack/* dependencies in sync with those used by bolt-js, @slack/web-api is now exported from bolt-js under the webApi export. Unless applications have specific version needs from the @slack/web-api package, apps should be able to import web-api from bolt instead:

import { webApi } from '@slack/bolt';
// now can use e.g. webApi.WebClient, etc.