Feature/promisify

[dxinteractive]

Addresses #286

dataparcels

• Added promisify to replace asyncValue and asyncChange. The new effect / async change reducer make this really easy.
  • Promises responses are queued so the order of promises being resolved / rejected is predicable
• Can be used in:
  • useParcel onChange for async saving
  • useParcel source for async loading
  • useParcel / useBuffer / Boundary derive for async derivation such as validation
  • any modifyUp

import promisify from 'react-dataparcels/promisify';
import useParcel from 'react-dataparcels/useParcel';

let personParcel = useParcel({
    source: () => ({
        value: 123
    }),
    onChange: promisify({
        key: 'save',
        effect: async ({value, meta}) => {
            await sendRequest(value);
            // you can return {value, meta} from here if you want to make a further update
        }
        // optionally set "last: true" if you only want to take the response from the last effect to be fired. Can be useful if you have new promises being created before old ones have resolved and you only care about the one based off the most recent value e.g. async validation of a text input
        // optionally set "revert: true" if you want it to revert changes when a promise is rejected. Useful for form submissions, as this will indicate to the buffer that it should retry sending the same changes again next time a form is submitted + any new changes
    })
});

personParcel.meta.saveStatus = 'pending' | 'resolved' | 'rejected';
personParcel.meta.saveError = latest error result, only when rejected