`bun build --target bun` and `bun build --compile` can emit a re-exported namespace binding without the underlying definition

[eyenalxai]

What version of Bun is running?

1.3.10+30e609e08

What platform is your computer?

Linux 6.19.6-arch1-1 x86_64 unknown

What steps can reproduce the bug?

https://github.com/eyenalxai/bun-bundle-bug-mre

This repository is a minimal workspace repro with three packages:

• @mini-bug/utils
• @mini-bug/codec
• @mini-bug/repro

The relevant code shape is:

// packages/mini-bug-utils/src/index.ts
import * as typed from './arrays/typed/index.js'
import * as u8 from './arrays/u8/pool.js'

export { typed, u8 }

// packages/mini-bug-utils/src/arrays/typed/index.ts
export { toDataView } from './misc.js'

// packages/mini-bug-codec/src/network/transports/intermediate.ts
import { typed } from '@mini-bug/utils'

const view = typed.toDataView(output)

// packages/mini-bug-repro/src/index.ts
import { u8 } from "@mini-bug/utils"
import { PaddedIntermediatePacketCodec } from "@mini-bug/codec"

Commands:

bun install
bun run source
bun run bundle:run
bun run compile:run

What they do:

"scripts": {
    "source": "bun run ./src/index.ts",
    "bundle:run": "bun build ./src/index.ts --outfile ./dist/index.js --target bun && bun run ./dist/index.js",
    "compile:run": "bun build --compile --target=bun-linux-x64-modern ./src/index.ts --outfile ./dist/index && ./dist/index"
  },

Current results:

• bun run source succeeds
• bun run bundle:run fails
• bun run compile:run fails

What is the expected behavior?

bun build --target bun and bun build --compile should preserve the same behavior as the source run.

Both generated outputs should run successfully and print:

14
8

What do you see instead?

ReferenceError: toDataView is not defined

bun run bundle:run:

Bundled 6 modules in 2ms

  index.js  1.61 KB  (entry point)

15 | };
16 | 
17 | // ../mini-bug-utils/src/arrays/typed/index.ts
18 | var exports_typed = {};
19 | __export(exports_typed, {
ReferenceError: toDataView is not defined
      at toDataView (/home/ulezot/Projects/js/bun-bundle-bug-mre/packages/mini-bug-repro/dist/index.js:20:31)
      at encode (/home/ulezot/Projects/js/bun-bundle-bug-mre/packages/mini-bug-repro/dist/index.js:41:31)
      at /home/ulezot/Projects/js/bun-bundle-bug-mre/packages/mini-bug-repro/dist/index.js:56:13
      at loadAndEvaluateModule (2:1)

bun run compile:run:

   [2ms]  bundle  6 modules
   [1ms] compile  ./dist/index
15 | };
16 | 
17 | // ../mini-bug-utils/src/arrays/typed/index.ts
18 | var exports_typed = {};
19 | __export(exports_typed, {
ReferenceError: toDataView is not defined
      at toDataView (/$bunfs/root/index:20:31)
      at encode (/$bunfs/root/index:41:31)
      at /$bunfs/root/index:56:13
      at loadAndEvaluateModule (2:1)

Additional information

The failure appears to depend on this combination:

• a namespace export from @mini-bug/utils
• a re-exported binding in packages/mini-bug-utils/src/arrays/typed/index.ts
• runtime access through typed.toDataView(...)

Two changes both make the repro stop failing:

1. Replace export { toDataView } from './misc.js' with a direct local definition in typed/index.ts.
2. Bypass typed/index.ts and import from ./arrays/typed/misc.js instead.

That suggests the bundled output is creating a getter for the re-exported binding without preserving the matching binding definition.

[github-actions]

Found 1 possible duplicate issue:

1. Re-export before any import causes referencing an undefined variable #15997

This issue will be automatically closed as a duplicate in 3 days.

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[eyenalxai]

Does not seem to happen on bun 1.3.9