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fix: better ES module support for App class#2632

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zimeg merged 3 commits intoslackapi:mainfrom
vercel-partner-solutions:main
Sep 9, 2025
Merged

fix: better ES module support for App class#2632
zimeg merged 3 commits intoslackapi:mainfrom
vercel-partner-solutions:main

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@malewis5
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@malewis5 malewis5 commented Aug 25, 2025

Summary

Fix ES module named export for App class

TypeScript's compilation of export { default as App } from './App' to CommonJS doesn't create proper named exports for ES module interoperability.

Before:

  // ❌ Fails in ES modules
  import { App } from '@slack/bolt';
  // ✅ Workaround required  
  import pkg from '@slack/bolt';
  const { App } = pkg;

After:

  // ✅ Now works!
  import { App } from '@slack/bolt';
  // ✅ Still backward compatible
  import pkg from '@slack/bolt';
  const { App } = pkg;

Details

  • Changed from export { default as App } re-export pattern to explicit import + export
  • Maintains full backward compatibility with existing CommonJS usage
  • Only affects the App class export to minimize risk

Notes

  • The same issue still exists for the receiver classes, but I wanted to scope this to only the App class.
  • Here is a useful tool to check these issues: npx --yes @arethetypeswrong/cli --from-npm @slack/bolt -f json
"problems": {
    "NamedExports": [
      {
        "kind": "NamedExports",
        "implementationFileName": "/node_modules/@slack/bolt/dist/index.js",
        "typesFileName": "/node_modules/@slack/bolt/dist/index.d.ts",
        "isMissingAllNamed": false,
        "missing": [
          "App",
          "Logger",
          "ExpressReceiver",
          "SocketModeReceiver",
          "HTTPReceiver",
          "AwsLambdaReceiver",
          "Installation",
          "InstallURLOptions",
          "InstallationQuery",
          "InstallationStore",
          "StateStore",
          "InstallProviderOptions"
        ]
      }
    ]
  }

@malewis5 malewis5 changed the title fix: better ES module support f fix: better ES module support for App class Aug 25, 2025
@zimeg zimeg added enhancement M-T: A feature request for new functionality semver:patch labels Aug 25, 2025
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zimeg commented Aug 25, 2025

Hey @malewis5! 👋 Thanks for sending this in and sharing such interesting tooling!

I'm a fan of this contribution in improvements for #2565 but I am not familiar of the strangeness the current release has? Testing with the following doesn't cause errors for me:

import { App } from "@slack/bolt";

const app = new App({ token: "example" });

await app.start();
$ npx tsc --allowJs --noEmit --esModuleInterop app.js

But please do let me know how else I can test this!

FWIW this "esModuleInterop" option is suspicious to me and removing it might require more upstream changes 👁️‍🗨️

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codecov bot commented Aug 25, 2025 •
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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.37%. Comparing base (73d15c1) to head (dbc8134).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files 
@@           Coverage Diff           @@
##             main    #2632   +/-   ##
=======================================
  Coverage   93.37%   93.37%           
=======================================
  Files          37       37           
  Lines        7581     7581           
  Branches      667      667           
=======================================
  Hits         7079     7079           
  Misses        497      497           
  Partials        5        5

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@malewis5
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malewis5 commented Aug 25, 2025

Hey @zimeg, we'll only see this crash at runtime not during typescript transpile. There's a good explanation of the issue here.

@malewis5
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malewis5 commented Aug 28, 2025

Here are two example repos that wrap Bolt with a framework:

@zimeg zimeg mentioned this pull request Sep 5, 2025
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zimeg approved these changes Sep 9, 2025
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@malewis5 Thank you for sharing those steps and more examples! 👾 ✨

I'm finding this change to be so helpful in similar setups of slack-samples/bolt-js-starter-template#119 while also remaining backward compatible so I think we're good to merge this for the next release 🚢

We should also revisit the other missing named exports noted in upcoming changes for #2565. I'll leave a comment with more detail, but am thinking named exports might be best?

Super appreciate this contribution and details shared! 🎁

@zimeg zimeg merged commit 44ceb2f into slackapi:main Sep 9, 2025
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@zimeg zimeg mentioned this pull request Sep 9, 2025
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@zimeg zimeg added this to the 4.4.1 milestone Sep 9, 2025
@zimeg zimeg mentioned this pull request Oct 21, 2025
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@grantjoy grantjoy mentioned this pull request Nov 23, 2025
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