fix(test): exclude @vitest/browser/context from vendor-aliases to fix missing server export

[kazupon]

Summary

Fixes the missing server export from @vitest/browser/context when using @storybook/addon-vitest with vite-plus.

resolve #1086

Root Cause

In vitest's browser mode, @vitest/browser/context is a virtual module, the BrowserContext plugin intercepts the bare specifier in resolveId and returns dynamically generated code (via generateContextFile()) that includes the server export with command RPC proxies, config, platform info, etc.

However, vite-plus injects a vitest:vendor-aliases plugin during re-packaging (in build.ts) that maps @vitest/* bare specifiers to static files in the dist directory.

Both plugins use enforce: 'pre', but vendor-aliases is registered before BrowserContext in the plugin array.

Since Vite executes same-enforce plugins in registration order, vendor-aliases resolves the bare specifier to the static context.js file before BrowserContext ever sees it.

The static context.js only exports { cdp, createUserEvent, locators, page, utils } — it does not include server, because that's supposed to come from the virtual module.

Normal flow (plain vitest — no vendor-aliases)

sequenceDiagram
    participant Browser
    participant ViteServer as Vite Browser Server
    participant BC as BrowserContext Plugin<br/>(resolveId)
    participant Gen as generateContextFile()

    Browser->>ViteServer: import "@vitest/browser/context"
    ViteServer->>BC: resolveId("@vitest/browser/context")
    BC-->>ViteServer: "\0vitest/browser" (virtual module ID)
    ViteServer->>BC: load("\0vitest/browser")
    BC->>Gen: generateContextFile()
    Gen-->>BC: Dynamic code with server, commands, config...
    BC-->>ViteServer: Virtual module source
    ViteServer-->>Browser: Module with { server, page, cdp, ... }

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Bug flow (vite-plus — vendor-aliases intercepts first)

sequenceDiagram
    participant Browser
    participant ViteServer as Vite Browser Server
    participant VA as vendor-aliases Plugin<br/>(resolveId) ← runs first
    participant BC as BrowserContext Plugin<br/>(resolveId) ← never called

    Browser->>ViteServer: import "@vitest/browser/context"
    ViteServer->>VA: resolveId("@vitest/browser/context")
    VA-->>ViteServer: "/path/to/dist/@vitest/browser/context.js" (static file)
    Note over BC: resolveId is never called<br/>because vendor-aliases already resolved it
    ViteServer-->>Browser: Static file (no server export)
    Browser->>Browser: SyntaxError: does not provide<br/>an export named 'server'

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Plugin registration order in the browser Vite server

1. vitest:vendor-aliases              ← enforce:'pre', registered first
2. vitest:browser                     ← enforce:'pre'
3. vitest:browser:tests               ← enforce:'pre'
4. vitest:browser:virtual-module:context (BrowserContext) ← enforce:'pre', registered last

Fix

Exclude @vitest/browser/context from the vendor-aliases plugin's vendorMap during re-packaging (build.ts).

This allows the bare specifier to pass through to the BrowserContext plugin, which correctly returns the virtual module with the server export.

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[kazupon]

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[chatgpt-codex-connector]

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