vitest-dev/vitest · error · Error

task "${name}" was not defined

Error message

task "${name}" was not defined

What it means

Thrown by the storage `get(name)` returned from `bench.compare(...)` (benchmark.ts:274) when you request a result by name that was not one of the registrations passed to `bench.compare()`. After a compare run, Vitest builds a result map keyed by registration name; looking up an undefined name means the task was never registered in that compare group.

Source

Thrown at packages/vitest/src/runtime/benchmark.ts:274

    period: data.period,
    totalTime: data.totalTime,
    rank: 0,
    fromStore: true,
  })

  const createCompareStorage = <T extends string>(
    results: Map<string, BenchResult>,
    fromResults?: Map<string, BaselineData>,
  ): BenchStorage<T> => {
    return {
      get(name: T) {
        const stored = fromResults?.get(name)
        if (stored) {
          return stored as BenchResult
        }
        const result = results.get(name)
        if (!result) {
          throw new Error(`task "${name}" was not defined`)
        }
        return result
      },
    }
  }

  interface TaskMeta { perProject?: true }

  const serializeBenchmark = (
    results: BenchResult[],
    name: string,
    taskMeta?: Map<string, TaskMeta>,
    fromTasks?: TestBenchmarkTask[],
  ): TestBenchmark => {
    const tasks: TestBenchmarkTask[] = results.map(result => ({
      name: result.name,
      latency: result.latency,
      throughput: result.throughput,

View on GitHub (pinned to d568f8ce37)

Solutions

1. Only call `storage.get(name)` with names that were registered in the same `bench.compare(...)` call.
2. Double-check the spelling/casing of the name against the registration.
3. Register the missing benchmark in the compare group if it should be part of the comparison.

Example fix

// before
const store = await bench.compare(
  bench('one', fn1),
  bench('two', fn2),
)
store.get('three') // throws

// after
store.get('one')

const validNames = new Set(registrations.map(r => r.name))
if (!validNames.has(requestedName)) throw new Error(`"${requestedName}" was not registered in bench.compare()`)

const isRegisteredName = (names: readonly string[], n: string): n is (typeof names)[number] =>
  (names as readonly string[]).includes(n)

When it happens

Trigger: Calling `storage.get('three')` when `bench.compare(oneReg, twoReg)` only registered `one` and `two`; a typo in the name; passing a different name string than the one used at registration.

Common situations: Refactoring benchmark names and forgetting to update lookups; copy-paste errors in the storage access; referencing a baseline name that wasn't included in the compare call.

Related errors

• `bench.compare()` requires at least 2 benchmarks, received $
• `bench.compare()` expects every argument to be the return va
• benchmark provider did not return a result for "${name}"
• `bench.from()` requires a name (string or named function) as
• `bench.from()` expects a string path or a function returning

AI-assisted analysis of vitest-dev/vitest@d568f8ce37 (2026-08-03). Data as JSON: /data/errors/e78d4340863a7804.json. Report an issue: GitHub.