See Promise State

Adds synchronous state inspection to the native promise

Provides a function of the form:

<R>(p: Promise<R>) => PromiseWithState<R>

The returned stateful promise is the same object as the provided promise, with the following additional properties:

• #resolved : boolean
• #rejected : boolean
• #complete : boolean

Useful for testing without introducting a mock for Promise. As such it is minorly limited; see caveats

Example

import assert from 'console';
import seePromiseState from 'see-promise-state';

const indefinite = seePromiseState(new Promise(() => {}));

assert(indefinite.complete === false);
assert(indefinite.resolved === false);
assert(indefinite.rejected === false);

const immediateResolution = seePromiseState(Promise.resolve());

assert(immediateResolution.complete === true);
assert(immediateResolution.resolved === true);
assert(immediateResolution.rejected === false);

const immediateRejection = seePromiseState(Promise.reject());

assert(immediateRejection.complete === true);
assert(immediateRejection.resolved === false);
assert(immediateRejection.rejected === true);

Caveats

Does not immediately apply to immediately resolving promises:

seePromiseState(Promise.resolve()).complete
// false

x = seePromiseState(Promise.resolve())
await sleep(0);
x.complete
// true

May not be correct for chains started before conversion

x = asyncTask();
x.then(() => console.log('A: ' + x.complete));
seePromiseState(x);
x.then(() => console.log('B: ' + x.complete));
await x;
// > 'A: false'
// > 'B: true'

Contributing

Feel free to make any contributions

The project uses yarn berry with zero-installs.

Build with: yarn build Test with: yarn test

If you use vscode, running yarn setupVSCode will setup vscode's typescript with yarn pnp.

If you use vscode launch configs are included for testing.