The one with txstate

This release contains a implementation, porting and expanding on txstate library. It provides:

• better error messages:

  Scenario 1

  
  Before -
  
  

  After -
  
  

  Scenario 2

  
  Before -
  
  

  After -
  
  

• Typed guards hence inferring context typestates

  Example

  // example picked from xstate docs
  let [flightMachine] = useStateMachine<FlightMachineContext>({ trip: 'oneWay' })({
    initial: 'editing',
    states: {
      editing: {
        on: {
          SUBMIT: {
            target: 'submitted',
            guard: (context): context is FlightMachineSubmittedContext => {
              if (context.trip === 'oneWay') {
                return !!context.startDate;
              } else {
                return (
                  !!context.startDate &&
                  !!context.returnDate &&
                  context.returnDate > context.startDate
                );
              }
            }
          }
        }
      },
      submitted: {}
    }
  })
  
  type FlightMachineEditingContext =
    { trip: 'oneWay' | 'roundTrip'
    , startDate?: Date
    , returnDate?: Date
    }
  type FlightMachineSubmittedContext =
    | { trip: 'oneWay'
      , startDate: Date
      }
    | { trip: 'roundTrip'
      , startDate: Date
      , returnDate: Date
      }
  
  type FlightMachineContext =
    | FlightMachineEditingContext
    | FlightMachineSubmittedContext
  
  expectType<FlightMachineContext>(flightMachine.context);
  if (flightMachine.value === 'submitted') {
    expectType<FlightMachineSubmittedContext>(flightMachine.context);
    
    if (flightMachine.context.trip === 'oneWay') {
      expectError(flightMachine.context.returnDate)
    }
  }

• New API, without the curried function workaround and with better support for typed events.

Credits: This was possible by the amazing effort of @devanshj