Bug : Client bundle fails with "Missing field 'code'" due to RolldownMagicString returned from renderChunk

[nihaal-turtle]

Summary

During pnpm run build (specifically the Client bundle gate running tsdown --config-loader native --env.DSH_BUILD_FACE client), bundling client packages (such as @deepseek-ai/dsh-client-ui-brand-official/client) crashes with the following error:

ERROR Error: Build failed with 1 error: Error: Missing field 'code'

Root Cause Analysis

In packages/client/tsdown.client.ts, the asyncChunkRequirePlugin and packageAssets plugins return transformed (an instance of RolldownMagicString) directly from their renderChunk hooks:

// asyncChunkRequirePlugin
return transformed.hasChanged() ? transformed : null

// packageAssets
return transformed

When tsdown runs with --config-loader native, Rolldown's bindingifyRenderChunk inspects the hook output:

if (ret instanceof RolldownMagicString) { ... }

Because tsdown.client.ts is loaded through the native loader, the RolldownMagicString constructor imported in the config file is not reference-identical to the constructor instance inside Rolldown's bundled module. As a result, ret instanceof RolldownMagicString evaluates to false.

Rolldown then falls back to extracting { code: ret.code, map: bindingifySourcemap(ret.map) }. Because RolldownMagicString does not have an own .code property (it produces its string output via .toString()), ret.code is undefined. Passing { code: undefined } across the NAPI bridge to Rust's BindingHookRenderChunkOutput causes Rust to reject the struct with:

Error: Missing field 'code'

---

Reproduction

1. Run pnpm run build (or specifically run the client bundle step):

   pnpm exec tsdown --config-loader native --env.DSH_BUILD_FACE client

2. Observe the failure during the Client bundle phase.

---

Current behavior

The build fails during Client bundle:

run-gates: start Client bundle
...
ERROR Error: Build failed with 1 error: Error: Missing field 'code'
run-gates: FAIL Client bundle (5.01s)

---

Expected behavior

pnpm run build and tsdown --config-loader native --env.DSH_BUILD_FACE client should build all client packages without errors.

---

Suggested Fix

In packages/client/tsdown.client.ts, have the renderChunk hooks return an explicit object with .code, .map, and .toString() (for test compatibility):

// In asyncChunkRequirePlugin:
if (!transformed.hasChanged()) return null
const codeResult = transformed.toString()
return {
  code: codeResult,
  map: transformed.generateMap().toString(),
  toString() {
    return codeResult
  },
}

// In packageAssets:
const codeResult = transformed.toString()
return {
  code: codeResult,
  map: transformed.generateMap().toString(),
  toString() {
    return codeResult
  },
}

---

Environment

• Node.js: >= 22.x / 24.x (with native TypeScript / strip-types support)
• Platform: macOS / Linux
• rolldown: 1.1.1
• tsdown: 0.22.2

[PerryLink]

The hooks return the MagicString, not { code, map }.

packages/client/tsdown.client.ts:479-498 is return transformed.hasChanged() ? transformed : null, and :650-656 is return transformed. Under --config-loader native the constructor identity differs across module graphs, so Rolldown's instanceof check misses and it reads .code from an object that only has .toString() — hence Missing field 'code'.

The explicit object shape you propose is the right fix; keep the toString() so any test comparing the hook result still works. A quick confirmation: the same build without --config-loader native should pass — if it does, the identity theory is settled.

I read the source only; I did not run pnpm run build here.

You can hand this to an AI assistant to prepare the two-hook patch.