feature(core): Add multi option for custom providers

[BrunnerLivio]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior?

No multi provider option

Issue Number: #770

What is the new behavior?

Support the multi option for providers

@Module({
  providers: [{
    provide: 'TEST',
    useValue: 'a',
    multi: true,
  },
  {
    provide: 'TEST',
    useValue: 'b',
    multi: true,
  }],
})
export class ApplicationModule { }

async function bootstrap() {
  const app = await NestFactory.createApplicationContext(ApplicationModule);
  console.log(app.get('TEST')); // ['a', 'b']
}
bootstrap();

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

I am looking forward to implementing a APP_INITIALIZER token for NestJS which could help with #1438

[coveralls]

Pull Request Test Coverage Report for Build 1484

• 25 of 25 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.04%) to 93.349%

---

Totals
Change from base Build 1414:	0.04%
Covered Lines:	3263
Relevant Lines:	3409

---

💛 - Coveralls

[BrunnerLivio]

Done! Please review @kamilmysliwiec

How does it work?

I tried to mimic the behavior of Angular.
When using the multi: true it creates two providers:

• The actual provider, same as before, but the token is different because the token willl be used for the multi provider.

• The multi provider is a factory which injects all the actual providers with the same token and returns them as an array

Mimic of the PRs behavior using the current public API to understand what is actually happening

@Module({
  providers: [
    {
      provide: 'TEST', // token gets changed in the background to `{ provide: 'TEST', useValue: 'test2', multi: true}`
      useValue: 'test1',
      multi: true,
    },
    {
      provide: 'TEST', // token gets changed in the background to `{ provide: 'TEST', useValue: 'test1', multi: true}`
      useValue: 'test1',
      multi: true
    }
    {
      // The multi provider
      provide: 'TEST',
      useFactory: (...args) => args,
      // Inject the previous defined providers
      inject: [{provide: 'TEST', useValue: 'test1', ... }, {provide: 'TEST', useValue: 'test2', ...}]
  ],
})
class TestModule { }

[thesayyn]

Waiting for this. I will migrate my backend to nestjs

[BrunnerLivio]

@thesayyn I am currently stuck because the current PR does not take the export of providers in consideration, which is definitely mandatory. I am currently trying to find a solution for this, but it is not easy, also because Angular behaves differently and therefore I can not proceed with my current Angular-inspired PR :/

[thesayyn]

Let me think a while I may can find a solution

[zuohuadong]

Is there any progress?

[wfairclough]

This is my first time looking at nestjs source, so mind my ignorance. I am a little confused what is happening here where the token is set to provider just moments after being set to provider.provide

[BrunnerLivio]

You’re right that is not needed. I had to do a lot of tinkering back then and seems like a unneeded statement is still present .

Nonetheless, this PR is currently on ice because I do not find time to look further into this at the moment. The current PR behaves similarly as in Angular. The problem is; Angular Injectables are global, whereas in Nest they are module specific (only public by exporting it). This makes it quite hard to implement in Nest but we hopefully get there!

[BrunnerLivio]

Closed in favor of #2460. I think I got it working, but it slightly different (Multi Providers will be handled as globals). I gotta need to take a break, it is 35 degrees here, my brain is boiling and I have no idea why my code even works (?!?). Will follow up tomorrow :-)

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.