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fix: apply cjs interop for truthy __esModule - #10363

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sheremet-va merged 3 commits into
vitest-dev:mainfrom
hi-ogawa:fix-apply-csj-interop-for-truthy-esmodule
May 18, 2026
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fix: apply cjs interop for truthy __esModule#10363
sheremet-va merged 3 commits into
vitest-dev:mainfrom
hi-ogawa:fix-apply-csj-interop-for-truthy-esmodule

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@hi-ogawa

@hi-ogawa hi-ogawa commented May 16, 2026 •
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Description

As written in #10359 (comment), Bun defines __esModule export for genuine esm in a way '__esModule' in mod === true but mod.__esModule === undefined. This behavior is Bun specific quirk, but Vitest applying interop based on __esModule property existence seems less conventional and can be naturally mitigated on Vitest side by detecting truthy __esModule. That's what PR changes.

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@hi-ogawa hi-ogawa changed the title fix: apply csj interop for truthy __esModule fix: apply cjs interop for truthy __esModule May 16, 2026
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hi-ogawa marked this pull request as ready for review May 16, 2026 06:39
@sheremet-va

sheremet-va commented May 16, 2026

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I don’t think we should change the behavior for bun. The interop is applied because Node cannot handle it specifically. deps.interopDefault is not required for bun at all, I think. It might be better to just disable it in that runtime

@hi-ogawa

hi-ogawa commented May 17, 2026 •
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I don’t think we should change the behavior for bun. The interop is applied because Node cannot handle it specifically. deps.interopDefault is not required for bun at all, I think. It might be better to just disable it in that runtime

Testing '__esModule' in value instead of value.__esModule doesn't look specifically intended though. I wouldn't be actually invested on Bun specific behavior to verify interopDefault is necessary or not, so if you are not merging this, I'll close this.

@sheremet-va

sheremet-va commented May 17, 2026 •
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I’m not stopping the merge, I just want to discuss this first

Testing '__esModule' in value instead of value.__esModule doesn't look specifically intended though

Why isn’t it intended? One use case I see is proxies throwing errors (I think this is why it’s “in” right now)

@hi-ogawa

hi-ogawa commented May 18, 2026

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Checking m.__esModule truthiness is the tradition as far as I understand since what babel and tsc do is something like Object.defineProperty(exports, "__esModule", { value: true }) https://www.typescriptlang.org/docs/handbook/2/modules.html#commonjs

Like this code

vitest/packages/mocker/src/browser/mocker.ts

Line 80 in 05a05a0

return m?.__esModule ? m : { ...((typeof m === 'object' && !Array.isArray(m)) || typeof m === 'function' ? m : {}), default: m }
and also some snippet in Vite also has m.__esModule ? ... style.

@sheremet-va

sheremet-va commented May 18, 2026

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Ok, I don't have a strong case against it, although I still believe for bun we should just change the default since it's not required in that environment.

@sheremet-va
sheremet-va merged commit 2b13547 into vitest-dev:main May 18, 2026
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@hi-ogawa
hi-ogawa deleted the fix-apply-csj-interop-for-truthy-esmodule branch May 18, 2026 07:42
eduvhc added a commit to iedora/platform that referenced this pull request May 29, 2026
@eduvhc
fix(ci): vitest 4.1.7 → 5.0.0-beta.3 (Bun __esModule interop)
b04686a 
vitest 4.1.7 testa `'__esModule' in mod` em vez de truthiness, e o Bun
deixa a propriedade presente mas undefined → `import { z } from 'zod'`
resolve para undefined dentro do node-symlinked-to-bun do oven/bun:1.3-debian.
Mac usa node real, por isso só o CI falha.

Corrigido upstream em vitest-dev/vitest#10363 (mergeado 2026-05-18),
ainda não disponível em stable. 5.0.0-beta.3 inclui o fix.

Falha original: 5 test files do products/menu (`z.object`/`z.enum` undefined)
em git.iedora.com/eduvhc/iedora/actions/runs/8/jobs/40.
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Bun runner makes import { z } from zod undefined

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@hi-ogawa @sheremet-va