Add plugins methods to typescript definition

Should plugins’s api methods be added in the core d.ts file? Or they should have their owns?

If they have their own, they should be merge into one when bundling the package?

I’m trying to use this library at another library, which is written with Typescript, and trying to use plugin methods, it’s driving me crazy. Any thoughts?

[ypresto]

I updated PR #418, another plugin type defs with module augmentation.

I think it is reasonable to stick on import dayjs from 'dayjs' singleton (not re-exporting extend()ed instance of dayjs) for convenience, because we (at least I) don’t want to change installed plugins place-by-place.

It is same as Vue’s plugin architecture, and official firebase plugin uses module augmentation to extend type declaration of Vue itself. Looks widely accepted way 😃

[bengry]

@iamkun option 3 isn’t necessarily a breaking change (though it can be). Consider that extend can still modify the prototype, and also return the new instance. This means that any existing usage will still work, but to get type safety you’ll need to re-export the instance created by the extend call. Regarding multiple plugins that relay on one another - you can chain them together (or even modify the extend method to take in an array of plugins):

import dayjs from 'daysjs';
import AdvancedFormat from 'dayjs/plugin/advancedFormat';
import RelativeTime from 'dayjs/plugin/relativeTime';

const dayJsWithRelativeTimeAndAdvancedFormat = dayjs.extend(AdvancedFormat).extend(RelativeTime); // type is inferred as dayjs.DayJS & AdvancedFormat & RelativeTime;

// or if we change the `extend` to be defined as:
export class DayJS {
  ...
  extend<T extends PluginFunc>(plugin: T): DayJS & T;
  extend<T extends PluginFunc, U extends PluginFunc>(plugin1: T, plugin2: U): DayJS & T & U;
  extend<T extends PluginFunc, U extends PluginFunc, V extends PluginFunc>(plugin1: T, plugin2: U, plugin3: V): DayJS & T & U & V;
}

you can call it as:
const dayJsWithRelativeTimeAndAdvancedFormat = dayjs.extend(AdvancedFormat, RelativeTime); // type is inferred as dayjs.DayJS & AdvancedFormat & RelativeTime;

The latter is similar to how Object.assign is defined and behaves as.

Do note that order is important here, so if AdvancedFormat would depend on RelativeTime being defined, the above would fail (the other way around though would work). Again, somewhat similar to how Object.assign behaves in regards to overriding properties defined in multiple objects.