Allow Service Invoke src shorthand (similar to events and transitions)

[ghost]

From the docs:

An invocation is defined in a state node's configuration with the invoke property, whose value is an object

invoke: { src: service }

For a service that doesn't need an id and other properties, it should be allowed to be defined as just the value of the src property, like invoke: service. This is consistent with the way events and transitions definitions can be done.

[davidkpiano]

This will probably be a V5 feature if we decide to do it.

[CodingDive]

Just out of curiosity: What kind of services don't have an onDone or onError handler? Even when invoking a callback as a service, I tend to define onError.

[Andarist]

It's up to you to implement those handlers and you probably should provide them 90+% of times.

By default callback services can only crash during initialization and machine services can't ever crash on their own so onError could be seen as not needed there, but you can always send error events on your own to trigger those handlers. You can also for example use escalate helper to forward a "caught" error from a promise service to a grandparent machine, if your structure looks like this:

• grandparent machine
• that invoked a parent machine
• that invoked a promise service

[davidkpiano]

In V5, activity services don't have an onDone (but they might have onError).