Make it possible to use our Pino transport with pino.transport()

[unflxw]

See also Slack conversation, Intercom conversation and Gist with workarounds.

It should be possible to use our Pino transport like the other transports documented in Pino's transport documentation:

pino(pino.transport({
  // this is an example, it's not the current location of the file
  target: '@appsignal/nodejs/pino',
  options: {...}
}))

This does not work with the current Pino transport, as it expects the client to be passed as the options, and the client is not serializable:

pino(pino.transport({
  target: '@appsignal/nodejs/dist/pino_transport.js',
  options: {
    // this fails, because the client is not serializable
    client: Appsignal.client,
    group: "pino"
  }
}))

This makes it really difficult to use it alongside other Pino transports, as described in Pino's documentation (e.g. to log to standard output as well as to AppSignal):

pino(pino.transport({
  targets: [
    { ... },
    // can't put AppSignal's transport here, see above
  ]
});

Instead, you have to know that it must be used as a destination and use pino.multistream() alongside pino.transport(), which is not documented as such anywhere:

pino(pino.multistream([
  { stream: AppsignalPinoTransport({ ... }) },
  { stream: pino.transport({ ... }) }
]));