inconsistency between .of and .fromPromise

[ftaiolivista]

Let's try this code.

import xs from 'xstream'


// TEST FROM xs.of()
const a = xs.of(' -a- ').debug(' -a- ')

const b = a.map(v => v + ' -b- ').debug(' -b- ')

const c = a.map(v => v + ' -c- ').debug(' -c- ')

const d = xs
    .merge(b, c)
    .map(v => v + ' -d- ')
    .debug(' -d- ')

d.addListener({
    next: () => {},
    error: () => {},
    complete: () => {}
})

// SAME CODE BUT WITH xs.fromPromise()
const a2 = xs.fromPromise(Promise.resolve(' -a- ')).debug(' -a2- ')

const b2 = a2.map(v => v + ' -b2- ').debug(' -b2- ')

const c2 = a2.map(v => v + ' -c2- ').debug(' -c2- ')

const d2 = xs
    .merge(b2, c2)
    .map(v => v + ' -d2- ')
    .debug(' -d2- ')

d2.addListener({
    next: () => {},
    error: () => {},
    complete: () => {}
})

The debug output is like
a-b-d-a-c-d
a2-b2-d2-c2-d2

Why when create the stream from promise the first debug is printed only one time at the beginning and when create it with .of() from const value the debug 'a' is printed two time?

P.S. Related stack overflow question

[ftaiolivista]

see #283