grafana/k6 · error

exported 'setup' must be a function

Error message

exported 'setup' must be a function

What it means

While scanning the entry module's exports, k6 special-cases the lifecycle names. An export named `setup` that is not a function cannot be invoked once before VU iterations, so the bundle loader rejects it immediately (bundle.go:224).

Source

Thrown at internal/js/bundle.go:224

					return
				}
				dec := json.NewDecoder(bytes.NewReader(data))
				dec.DisallowUnknownFields()
				if err = dec.Decode(&b.Options); err != nil {
					if uerr := json.Unmarshal(data, &b.Options); uerr != nil {
						// Beautify the error so we can try to show the user the key and potential value that is failing to parse
						uerr = beautifyOptionsJSONUnmarshalError(data, uerr)
						err = errext.WithAbortReasonIfNone(
							errext.WithExitCodeIfNone(uerr, exitcodes.InvalidConfig),
							errext.AbortedByScriptError,
						)
						return
					}
					b.preInitState.Logger.WithError(err).Warn("There were unknown fields in the options exported in the script")
					err = nil
				}
			case consts.SetupFn:
				err = errors.New("exported 'setup' must be a function")
				return
			case consts.TeardownFn:
				err = errors.New("exported 'teardown' must be a function")
				return
			}
		}
	})
	<-ch
	if err != nil {
		return err
	}

	if len(b.callableExports) == 0 {
		return errors.New("no exported functions in script")
	}

	return nil
}

View on GitHub (pinned to 93accf6570)

Solutions

1. Declare it as a function: `export function setup() { ... }`
2. If the export is data, rename it so it does not collide with the reserved lifecycle name

Example fix

// before
export const setup = { token: 'abc' };

// after
export const config = { token: 'abc' };
export function setup() { return config; }

if (typeof setup !== 'undefined' && typeof setup !== 'function') { throw new Error('setup export must be a function'); }

const isValidSetup = (v) => v === undefined || typeof v === 'function';

When it happens

Trigger: `export const setup = 'x'`, `export let setup = 42`, or re-exporting a non-function binding named `setup` from the main module; fires during script load, before anything runs.

Common situations: Typos like `export function setups()`; refactors that turned setup into a config object or constant; codegen emitting `export const setup = {...}`.

Related errors

• exported 'teardown' must be a function
• no exported functions in script
• no gRPC connection, you must call connect first
• open() can't be used with an empty filename
• predicate function is not callable

AI-assisted analysis of grafana/k6@93accf6570 (2026-08-15). Data as JSON: /api/errors/ab9fb0b2530c4caa. Report an issue: GitHub.