MyCommand.registerWithSubCommands() when subcommands are inside another module

[Sefrancois]

Hello there 👋

I encountered an issue when trying to work with the method registerWithSubCommands() inside my module that exposes my CLI.

What we try to do is to provide & exports a SubCommand from one module and imports it to our CliModule like following :

@SubCommand({
    name: "some-sub-command",
})
export class MySubCommand extends CommandRunner {
    constructor(private readonly someProvider: SomeProvider) {
        super();
    }

    public override run(): void {
        // Do something ...
    }
}

Here is how it's instantiated through some random module :

@Module({
    imports: [SomeModule],
    providers: [
        SomeProvider,
        {
            provide: MySubCommand,
            inject: [SomeProvider],
            useFactory: (someProvider: SomeProvider): MySubCommand => {
                return new MySubCommand(someProvider);
            }
        }
    ],
    exports: [MySubCommand],
})
export class SomeModule {
}

Here we have our command called MyCommand :

@Command({
    name: "my-command",
    subCommands: [MySubCommand],
})
export class MyCommand extends CommandRunner {
    public override run(): void {
       // Do nothing
    }
}

And here is how we want to expose our CLI through our CliModule :

@Module({
    imports: [SomeModule],
    providers: [...MyCommand.registerWithSubCommands()],
})
export class CliModule {
}

Our error when we try to run our application is that Nest can't resolve MySubCommand dependencies (SomeProvider in that case) as it's not exposed through SomeModule. The only thing we export is MySubCommand. However, our main problem is more about why does Nest try to instantiate MySubCommand again since it's already been instantiated and available through SomeModule that we import in our CliModule ?

[jmcdo29]

Could you get me a repository that has this setup? nest-commander shouldn't be trying to make a new instance of that command, but it may be the moduleRef.get() that is having issues

[Sefrancois]

Hello !

Thanks for your answer !

You'll find some code that reproduces the example in here : https://github.com/Sefrancois/subcommand-issue-example

I joined a screenshot of the error inside the README.md

[jmcdo29]

Ah! I see. So this actually has to do with how registerWithSubCommands works. That static method will find all of the subcommands mentioned in the metadata and add them as providers to the current module. This means that in the CliModule you're trying to re-create the subcommands because that's how the providers arrays work in NestJS.

If you add SomeProvider to the exports of your SomeModule and remove the DoSomethingMoreAccurateSubCommand provider from it, it'll all work as expected.

I know that might not be ideal for you though

[Sefrancois]

Hello there !

Thanks for your answer 😄

We found out a way to make it work and it was that simple that ... We didn't think of it earlier.

In fact, we don't have to call the method registerWithSubCommands since we have already instantiated every single sub command and exported it from SomeModule.

So all we have to do in our CliModule is the following and it works like a charm :

@Module({
    imports: [SomeModule],
    providers: [MyCommand],
})
export class CliModule {
}

As MySubCommand has already been registered as a provider of SomeModule and has been set as an exported provider from SomeModule, Nest can instantiate MyCommand without trying to instantiate MySubCommand again but use existing value.

Just wanted to share it in case somebody else faces the same "issue" 😄