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Slack Edge

The slack-edge library is a Slack app development framework designed specifically for the following runtimes:

Not only does it work with the above, but it also functions with the latest versions of Deno, Bun, and Node.js.

This framework draws significant inspiration from Slack’s Bolt framework, but its design does not strictly follow the bolt-js blueprint. Key differences include:

  • Edge function ready: Out-of-the-box edge function (e.g., Cloudflare Workers) support
  • TypeScript focused: Enhances type safety and clarifies typings for developers
  • Lazy listener enabled: bolt-python’s lazy listener feature is provided out of the box
  • Zero additional dependencies: No other dependencies required beyond TypeScript types and slack-web-api-client (our fetch-function-based Slack API client)

Getting Started

Run with Deno

import {
  SlackApp,
  SlackEdgeAppEnv,
} from "https://deno.land/x/slack_edge@1.0.0/mod.ts";

const app = new SlackApp<SlackEdgeAppEnv>({
  env: {
    SLACK_SIGNING_SECRET: Deno.env.get("SLACK_SIGNING_SECRET")!,
    SLACK_BOT_TOKEN: Deno.env.get("SLACK_BOT_TOKEN"),
    SLACK_LOGGING_LEVEL: "DEBUG",
  },
});

// Add listeners here

await Deno.serve({ port: 3000 }, async (request) => {
  return await app.run(request);
});

You can run the app by:

# Terminal A
deno run --watch --allow-net --allow-env my-app.ts
# Terminal B
brew install cloudflare/cloudflare/cloudflared
cloudflared tunnel --url http://localhost:3000

Run with Deno (Socket Mode: Experimental)

Important Notice: The Socket Mode support provided by slack-edge is still experimental and is not designed to handle reconnections for production-grade applications. It is recommended to use this mode only for local development and testing purposes.

Thanks to Deno’s built-in WebSocket implementation, you can quickly and easily run a Socket Mode app as below:

import {
  SlackApp,
  SlackSocketModeAppEnv,
} from "https://deno.land/x/slack_edge@1.0.0/mod.ts";

const app = new SlackApp<SlackSocketModeAppEnv>({
  env: {
    SLACK_APP_TOKEN: Deno.env.get("SLACK_APP_TOKEN")!,
    SLACK_BOT_TOKEN: Deno.env.get("SLACK_BOT_TOKEN"),
    SLACK_LOGGING_LEVEL: "DEBUG",
  },
});

// Add listeners here

await app.connect();
setTimeout(() => {}, Number.MAX_SAFE_INTEGER);

You can run this app by deno run --watch --allow-net --allow-env my-app.ts.

Reference

Middleware

This framework offers ways to globally customize your app’s behavior, like you do when developing web apps. A common example is to attach extra data to the context object for following listeners.

Pattern Description
app.beforeAuthorize The passed function does something before calling authorize() function. If this method returns SlackResponse, the following middleware and listeners won’t be executed.
app.afterAuthorize / app.use / app.middleware The passed function does something right after calling authorize() function. If this method returns SlackResponse, the following middleware and listeners won’t be executed.

ack / lazy Functions

You may be unfamiliar with the “lazy listener” concept in this framework. To learn more about it, please read bolt-python’s documentation: https://slack.dev/bolt-python/concepts#lazy-listeners

The ack function must complete within 3 seconds, while the lazy function can perform time-consuming tasks. It’s important to note that not all request handlers support the ack or lazy functions. For more information, please refer to the following table, which covers all the patterns in detail.

Starting from v0.9, if desired, you can execute lazy listeners after the completion of their ack function. To customize the behavior in this manner, you can pass startLazyListenerAfterAck: true as one of the arguments in the App constructor.

Pattern Description ack function lazy function
app.command The passed function handles a slash command request pattern. If the function returns a message, the message will be posted in the channel where the end-user invoked the command. ◯ ◯
app.event The passed function asynchronously does something when an Events API request that matches the constraints comes in. Please note that manually acknowledge a request is unsupported. You can pass only one function, which can be executed as a lazy listener. x ◯
app.function [experimental] The passed function asynchronously does something when a “function_executed” event request that matches the constraints comes in. Please note that manually acknowledge a request is unsupported. You can pass only one function, which can be executed as a lazy listener. Also, this feature is still in beta so that the details could be changed on the Slack plaform side until it’s GAed. x ◯
app.message / app.anyMessage The passed function asynchronously does something when an a message event comes in. Please note that manually acknowledge a request is unsupported. You can pass only one function, which can be executed as a lazy listener. If the message pattern argument can be any of string, regexp, and undefined. When you pass undefined, the listener matches all messages. x ◯
app.shortcut / app.globalShortcut / app.messageShortcut The passed function handles a global/message shortcut request pattern. Please note that returning a message text in the ack function does not work for shortcuts. Instead, you can use context.respond for it. ◯ ◯
app.action The passed function handles a user interaction on a Block Kit component such as button clicks, item selection in a select menu, and so on. ◯ ◯
app.options The passed function handles an external data source reqeust for Block Kit select menus. You cannnot respond to this request pattern asynchronously, so slack-edge enables developers to pass only ack function, which must complete within 3 seconds, here. ◯ x
app.view / app.viewSubmission / app.viewClosed The passed function handles either a modal data submission or the “Close” button click event. ack function can return various response_actions (errors, update, push, clear) and their associated data. If you want to simply close the modal, you don’t need to return anything. ◯ ◯