[RFC] createInjectionToken generic type and optional factory about ngxtension-platform

[nartc]

1. For the first case where you need optional factory and multi, you can use the following workaround for now

// note the "!" non-null assertion.
export const [injectFn, provideFn] = createInjectionToken<MyType>(() => null!, { multi: true });

2. provideFn() accepting a factory is tricky. What's the main difference between the following?

export const [injectFn, provideFn] = createInjectionToken(() => {
    const foo = inject(FOO, { optional: true });
    if (foo) return 'something'
    return 'something else';
}, { multi: true });
provideFn();

// versus
provideFn(() => { const foo = inject(FOO); if (foo) return 'something' return 'something else' })

[wanoo21]

Okay, not-null null sounds cool :) But it's okay for this approach!

So what I'm trying to achieve is to have a multi-token that contains some objects. Sometimes, I need to inject other tokens to create the object.

For example:

export const [injectBlocks, provideBlock] = createInjectionToken((): MyBlock[] => [], { multi: true });

Adding needed blocks:

// image.block.ts
provideBlock(() => {
 const locale = inject(LOCALE);
 return {
   type: 'image',
   align: locale === 'en-US' ? 'left' : 'right' // just an example
 }
})

// text.block.ts
provideBlock(() => {
 const direction = inject(Directionality);
 return {
   type: 'text',
   textAlign: direction.value === 'ltr' ? 'left' : 'right'
 }
})

Somewhere in the main component:

readonly blocks = injectBlocks(); // -> [{type: 'image' ...}, {type: 'text', ...}]

Is there a workaround for this now?

[nartc]

hm....there's not a workaround now unfortunately. I'll add support for passing factories into provideFn

[wanoo21]

@nartc that'd be amazing, thank you!