Angular providers: Use existing or create one if not provided

In Angular 2+, how can I provide a new instance of an Injectable only if there's no instance existing?

I searched and found none so I tried useFactory. This is my code so far:

{
provide: ColorsService,
useFactory: (colorService: ColorsService, colors: string[]) => {
if (colorService) return colorService;
return new ColorsService(colors);
},
deps: [ColorsService, MY_COLORS],
},


Besides the fact that I'm injecting the MY_COLORS token manually, I get a weird error:

Error: Circular dep for ColorsService
​

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