Solvedangular Can't resolve all parameters for .... This will become an error in Angular v6.x

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[x] Bug report  
[ ] Performance issue
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question
[ ] Other... Please describe:

I have 4 classes:

• Class A, @Injectable
• Class B, abstract, NON injectable, extends A
• Class C, @Injectable, extends B
• Class D, @Injectable, extends B

classes A, C and D are used as Services and correctly added to the providers list of my module. Class B is NOT used as a service.

Current behavior

Everything works fine but I got this warning:

Can't resolve all parameters for ClassBService in /path/to/class-b.service.ts: ([object Object], ?). This will become an error in Angular v6.x

Expected behavior

Not sure if some action on my side is required or this warning should not be displayed.

Demo

Clone the repository, run npm install and then ng build --prod. You'll see the warning.

https://github.com/ShinDarth/angular-test/

FrancescoBorzi/angular-test@4101bc5

Environment

Angular CLI: 1.7.4
Node: 8.10.0
OS: linux x64
Angular: 5.2.11
... animations, common, compiler, compiler-cli, core, forms
... http, language-service, platform-browser
... platform-browser-dynamic, router

@angular/cli: 1.7.4
@angular-devkit/build-optimizer: 0.3.2
@angular-devkit/core: 0.3.2
@angular-devkit/schematics: 0.3.2
@ngtools/json-schema: 1.2.0
@ngtools/webpack: 1.10.2
@schematics/angular: 0.3.2
@schematics/package-update: 0.3.2
typescript: 2.6.2
webpack: 3.11.0

If I can help someone... I solved my issue

I had this error. The problem for me was a missing @Inject.

I created an InjectionToken to pass a config to my Service from the forRoot,
but I was missing the @Inject("myTokenName") in my Service.

So when building with --aot and --build-optimizer=true or --build-optimizer=false
I had the warning!

After adding the @Inject problem solved!!

Having this problem too. Angular 7 complaining only when ng build is called with --prod / --aot.
Its still a warning (not an error), but its annoying to have logged. I can also confirm that its different to the duplicate tickets marked above.

I had this issue because I am using generics to reduce code duplication. Here is my original code that was causing the warning:

@Injectable()
export abstract class MyBaseClass<S> {
  protected constructor(protected readonly service: S) {}
  
  // .. some code
}

Since this class is abstract it will never be injected anywhere, thus it should not be decorated with @Injectable(). Removing it makes compiler happy again.

If you need @Injectable then @Inject needs to be also provided - the solution proposed by @tonysamperi.

I confirm that the bug is still present using Angular 7, and it' still saying:

This will become an error in Angular v6.x

I had this issue because I am using generics to reduce code duplication. Here is my original code that was causing the warning:

@Injectable()
export abstract class MyBaseClass<S> {
  protected constructor(protected readonly service: S) {}
  
  // .. some code
}

Since this class is abstract it will never be injected anywhere, thus it should not be decorated with @Injectable(). Removing it makes compiler happy again.

If you need @Injectable then @Inject needs to be also provided - the solution proposed by @tonysamperi.

It works, when you remove injectable decorator, then your abstract/generic class compiles successfully. Thanks.