Pluggable formatters

I propose we make the formatters that may be used in translations officially pluggable.

Motivation

Our API returns monetary values as objects that look like this:

interface Money {
  value: number; // integer
  currency: 'USD' | 'EUR';
  e?: number; // default: -2
}

We have added this method to our IntlService:

formatMoney(money: Money, options, ctx) {
  const { value, currency, e = -2 } = money;
  const normalizedValue *= 10 ** e;

  return super.formatNumber(normalizedValue, {
    format: currency,
    ...options,
  }, ctx);
}

And also added an accompanying helper:

import BaseHelper from 'ember-intl/helpers/-format-base';
import Money from 'client/interfaces/money';

 export default class FormatMoneyHelper extends BaseHelper {
  format(value: Money, options): string {
    return this.intl.formatMoney(value, options);
  }
}

We represent monetary values like this for two reasons:

• to avoid floating point arithmetic imprecision when performing calculations with these values, as 0.1 + 0.2 !== 0.3
• to automatically deal with different currencies

This has been working great for us so far. But we can’t yet use this formatter in translations directly, like:

amountDue: 'Amount due: {due, money}'

To be able to use this formatter in translations directly, we would need to add a formatter to IntlService#_formatters:

https://github.com/ember-intl/ember-intl/blob/4ab18a4524c2f42c57fa4533cbffdce2dea9a1d1/addon/services/intl.js#L107-L113

Proposal

We could of course continue monkey-patching our way through ember-intl, but I think that making the formatter system officially pluggable would be quite useful.

I think we should open up the formatter system officially, so that users / addons can add custom formatters.

Open Questions

• How does ember-intl / the message formatter find the formatters? Via the ember-resolver container maybe?
• What about template helpers? Should the addons just be responsible for providing such helpers?
• What about IntlService#formatXXX methods?

[snewcomer]

https://github.com/messageformat/messageformat/search?utf8=✓&q=rtl&type=

Ah I guess I was referring to this. Looks like it detects rtl locale. Happens via ‘biDiSupport’ config variable

[jasonmit]

Going to close this for now as it’s out of scope for this project.

I just finished updating the intl-messageformat compiler & parser. If and when we support this, it will need to happen upstream. Track this issue if you’re interested: https://github.com/formatjs/formatjs/issues/20