TypeError: Cannot read properties of undefined (reading 'pool') when rendering errors with vitest 4.x

[tuntisz]

Description

When using evalite with vitest 4.x, if an eval test throws an error, the error rendering crashes with:

TypeError: Cannot read properties of undefined (reading 'pool')

This masks the actual underlying error, making debugging impossible.

Root Cause

In node_modules/vitest/dist/chunks/index.456_DGfR.js:2983:

if (options.task?.file.pool === "browser" && project.browser)

The optional chaining on task doesn't protect against task.file being undefined. When task exists but task.file is undefined, accessing .pool throws.

This is triggered from evalite's reporter in renderErrorsSummary (node_modules/evalite/dist/reporter/rendering.js:75).

Stack Trace

TypeError: Cannot read properties of undefined (reading 'pool')
    at Object.parseErrorStacktrace (file:///node_modules/vitest/dist/chunks/index.456_DGfR.js:2983:26)
    at printErrorInner (file:///node_modules/vitest/dist/chunks/index.456_DGfR.js:3015:25)
    at printErrorInner (file:///node_modules/vitest/dist/chunks/index.456_DGfR.js:3064:3)
    at printError (file:///node_modules/vitest/dist/chunks/index.456_DGfR.js:2970:9)
    at Logger.printError (file:///node_modules/vitest/dist/chunks/cli-api.C7sYjHmQ.js:6551:3)
    at renderErrorsSummary (file:///node_modules/evalite/dist/reporter/rendering.js:75:24)
    at EvaliteReporter.onTestRunEnd (file:///node_modules/evalite/dist/reporter.js:134:9)

Reproduction Steps

1. Create a minimal evalite setup with vitest 4.x:

{
  "devDependencies": {
    "@modelcontextprotocol/sdk": "^1.24.3",
    "evalite": "0.19.0",
    "vitest": "4.0.15"
  }
}

2. Create an eval that makes an HTTP request that fails (e.g., MCP client connecting to a server that isn't running):

// evals/example.eval.ts
import { evalite } from 'evalite'
import { Client } from '@modelcontextprotocol/sdk/client/index.js'
import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/streamableHttp.js'

evalite('mcp-eval', {
  data: async () => [{ input: 'test' }],
  task: async () => {
    // This will throw: TypeError: fetch failed
    // Caused by: Error: connect ECONNREFUSED 127.0.0.1:443
    const client = new Client({ name: 'test', version: '1.0.0' })
    const transport = new StreamableHTTPClientTransport(
      new URL('https://localhost/mcp')
    )
    await client.connect(transport)
    return 'done'
  },
  scorers: [],
})

3. Run npx evalite

4. Instead of seeing the actual error:

TypeError: fetch failed
 ❯ StreamableHTTPClientTransport.send node_modules/@modelcontextprotocol/sdk/dist/esm/client/streamableHttp.js:315:30

Caused by: Error: connect ECONNREFUSED 127.0.0.1:443
Serialized Error: { errno: -61, code: 'ECONNREFUSED', syscall: 'connect', address: '127.0.0.1', port: 443 }

You get the unhelpful:

TypeError: Cannot read properties of undefined (reading 'pool')

Environment

• evalite: 0.19.0
• vitest: 4.0.15
• Node: 24.x

Expected Behavior

Evalite should properly display the actual error from the failing eval task (the ECONNREFUSED error), not crash while trying to render it.

Suggested Fix

When calling vitest's printError / parseErrorStacktrace, ensure the task object has the required file property, or pass undefined for the task if file information is not available.