fix(mocker): fix mock transform with class #9421

hi-ogawa · 2026-01-09T11:04:14Z

Description

The bug is found when investigating Vite 8 #9415.

vitest/test/core/test/mocking/automocking-class-inheritence.test.ts

Lines 45 to 51 in f8879a8

    
           class Bar { 
        
             doSomething() {} 
        
           } 
        
           const Zoo = vi.mockObject(class Zoo extends Bar { 
        
             ownMethod() {} 
        
           })

The transform scope issue didn't manifest with esbuild ts transform since esbuild was deconflicting by itself by Bar -> Bar2. Now this manifested with Oxc since inner Bar were kept as is.

The test case added here is raw js, so it fails without the fix.

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hi-ogawa · 2026-01-09T11:04:54Z

test/core/test/injector-mock.test.ts

+      const Bar = class Foo {
+        static create() {
+          return new Foo()
+        }
+      }"


Without the fix, this becomes

const Bar = class Foo { static create() { return new __vi_import_0__.Foo() } }

hi-ogawa · 2026-01-09T11:05:16Z

test/core/test/injector-mock.test.ts

+        class Bar {
+          test() {}
+        }
+        const Zoo = class Zoo extends Bar {}


Without fix, this becomes:

class Bar { test() {} } const Zoo = class Zoo extends __vi_import_0__.Bar {}

hi-ogawa · 2026-01-09T11:06:17Z

packages/mocker/src/node/esmWalker.ts

+      else if (node.type === 'ClassDeclaration' && node.id) {
+        // A class declaration name could shadow an import, so add its name to the parent scope
+        const parentScope = findParentScope(parentStack)
+        if (parentScope) {
+          setScope(parentScope, node.id.name)
+        }
+      }
+      else if (node.type === 'ClassExpression' && node.id) {
+        // A class expression name could shadow an import, so add its name to the scope
+        setScope(node, node.id.name)
+      }


Vite SSR transform has this already, so I just copied from there https://github.com/vitejs/vite/blob/964c718a382ff46ec1f906d7d6bc3f135a6dcd3f/packages/vite/src/node/ssr/ssrTransform.ts#L623-L631

This PR contains the following updates: | Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) | |---|---|---|---| | [@vitest/coverage-v8](https://github.com/vitest-dev/vitest/tree/main/packages/coverage-v8#readme) ([source](https://github.com/vitest-dev/vitest/tree/HEAD/packages/coverage-v8)) | [`4.0.16` → `4.0.18`](https://renovatebot.com/diffs/npm/@vitest%2fcoverage-v8/4.0.16/4.0.18) | ![age](https://developer.mend.io/api/mc/badges/age/npm/@vitest%2fcoverage-v8/4.0.18?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/@vitest%2fcoverage-v8/4.0.16/4.0.18?slim=true) | | [vitest](https://vitest.dev) ([source](https://github.com/vitest-dev/vitest/tree/HEAD/packages/vitest)) | [`4.0.16` → `4.0.18`](https://renovatebot.com/diffs/npm/vitest/4.0.16/4.0.18) | ![age](https://developer.mend.io/api/mc/badges/age/npm/vitest/4.0.18?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/vitest/4.0.16/4.0.18?slim=true) | --- ### Release Notes <details> <summary>vitest-dev/vitest (@vitest/coverage-v8)</summary> ### [`v4.0.18`](https://github.com/vitest-dev/vitest/releases/tag/v4.0.18) [Compare Source](vitest-dev/vitest@v4.0.17...v4.0.18) ##### 🚀 Experimental Features - 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Support openTelemetry for browser mode - by [@hi-ogawa](https://github.com/hi-ogawa) in [#9180](vitest-dev/vitest#9180) [<samp>(1ec3a)</samp>](vitest-dev/vitest@1ec3a8b68) - Support TRACEPARENT and TRACESTATE environment variables for OpenTelemetry context propagation - by [@Copilot](https://github.com/Copilot), **hi-ogawa** and [@hi-ogawa](https://github.com/hi-ogawa) in [#9295](vitest-dev/vitest#9295) [<samp>(876cb)</samp>](vitest-dev/vitest@876cb84c2) ##### 🐞 Bug Fixes - Improve asymmetric matcher diff readability by unwrapping container matchers - by [@Copilot](https://github.com/Copilot), **sheremet-va**, **hi-ogawa** and [@hi-ogawa](https://github.com/hi-ogawa) in [#9330](vitest-dev/vitest#9330) [<samp>(b2ec7)</samp>](vitest-dev/vitest@b2ec724a8) - Improve runner error when importing outside of test context - by [@sheremet-va](https://github.com/sheremet-va) in [#9335](vitest-dev/vitest#9335) [<samp>(2dd3d)</samp>](vitest-dev/vitest@2dd3dd839) - 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by [@hi-ogawa](https://github.com/hi-ogawa) in [#9294](vitest-dev/vitest#9294) [<samp>(b6778)</samp>](vitest-dev/vitest@b67788c69) - Fix invalid project token for artifacts assets - by [@hi-ogawa](https://github.com/hi-ogawa) in [#9321](vitest-dev/vitest#9321) [<samp>(caa7d)</samp>](vitest-dev/vitest@caa7d73d4) - Log `ErrorEvent.message` when unhandled `ErrorEvent.error` is null - by [@hi-ogawa](https://github.com/hi-ogawa) in [#9322](vitest-dev/vitest#9322) [<samp>(5d84e)</samp>](vitest-dev/vitest@5d84eeb91) - Support `fileParallelism` on an instance - by [@sheremet-va](https://github.com/sheremet-va) in [#9328](vitest-dev/vitest#9328) [<samp>(15006)</samp>](vitest-dev/vitest@150065459) - **coverage**: - Remove unnecessary `istanbul-lib-source-maps` usage - by [@AriPerkkio](https://github.com/AriPerkkio) in [#9344](vitest-dev/vitest#9344) [<samp>(b0940)</samp>](vitest-dev/vitest@b09405375) - Apply patch from [istanbuljs/istanbuljs#837](istanbuljs/istanbuljs#837) - by [@AriPerkkio](https://github.com/AriPerkkio) and **sapphi-red** in [#9413](vitest-dev/vitest#9413) and [#837](vitest-dev/vitest#837) [<samp>(e05ce)</samp>](vitest-dev/vitest@e05cedbf4) - **fsModuleCache**: - Don't store importers in cache - by [@sheremet-va](https://github.com/sheremet-va) in [#9422](vitest-dev/vitest#9422) [<samp>(75136)</samp>](vitest-dev/vitest@751364eec) - Add importers alongside importedModules - by [@sheremet-va](https://github.com/sheremet-va) in [#9423](vitest-dev/vitest#9423) [<samp>(59f92)</samp>](vitest-dev/vitest@59f92d403) - **mocker**: - Fix mock transform with class - by [@hi-ogawa](https://github.com/hi-ogawa) in [#9421](vitest-dev/vitest#9421) [<samp>(d390e)</samp>](vitest-dev/vitest@d390eb527) - **pool**: - Validate environment options when reusing the worker - by [@sheremet-va](https://github.com/sheremet-va) in [#9349](vitest-dev/vitest#9349) [<samp>(a8a88)</samp>](vitest-dev/vitest@a8a8836e3) - 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**webdriverio**: - Fall back to WebDriver Classic [#9244](vitest-dev/vitest#9244) - by [@JustasMonkev](https://github.com/JustasMonkev) in [#9373](vitest-dev/vitest#9373) and [#9244](vitest-dev/vitest#9244) [<samp>(c23dd)</samp>](vitest-dev/vitest@c23dd11bd) ##### [View changes on GitHub](vitest-dev/vitest@v4.0.16...v4.0.17) </details> --- ### Configuration 📅 **Schedule**: Branch creation - Between 12:00 AM and 03:59 AM, on day 1 of the month ( * 0-3 1 * * ) (UTC), Automerge - Between 12:00 AM and 03:59 AM ( * 0-3 * * * ) (UTC). 🚦 **Automerge**: Enabled. ♻ **Rebasing**: Whenever PR is behind base branch, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about these updates again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).  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fix(mocker): fix mock transform with class

f8879a8

hi-ogawa commented Jan 9, 2026

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hi-ogawa marked this pull request as ready for review January 9, 2026 11:40

sheremet-va approved these changes Jan 9, 2026

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sheremet-va merged commit d390eb5 into vitest-dev:main Jan 9, 2026
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chore(deps): update vitest monorepo to v4.0.17 (patch) simonkberg/simon.dev#1504

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fix(mocker): fix mock transform with class #9421

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hi-ogawa commented Jan 9, 2026 •

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	class Bar {
	doSomething() {}
	}

	const Zoo = vi.mockObject(class Zoo extends Bar {
	ownMethod() {}
	})

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fix(mocker): fix mock transform with class #9421

fix(mocker): fix mock transform with class #9421

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hi-ogawa commented Jan 9, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Description

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

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hi-ogawa commented Jan 9, 2026 •

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