TraceWriter

Sink for structured or human-readable trace output from the runtime and handlers.

Inject a custom implementation via makeHsm to collect traces in tests, forward to OpenTelemetry, or suppress console noise in CI.

Methods

write()

write<Context, Protocol>(hsm, msg): void

Record one trace line for a machine instance.

Type Parameters

Context

Context

Domain context type of the machine being traced

Protocol

Protocol extends { } | undefined

Event/service vocabulary of the machine being traced

Parameters

hsm

Properties<Context, Protocol>

Read-only machine properties (Properties.currentStateName, Properties.traceHeader, etc.) at the time of the write

msg

any

Payload to record. Strings are formatted as `${traceHeader}${currentStateName}: ${msg}` by the default console writer; non-strings are passed through unchanged (e.g. Error objects on failure paths)

Returns

void

Remarks

Handlers may call this.traceWriter.write(this.hsm, 'my message') for ad-hoc logging that respects the same header and state prefix as runtime traces.