Middleware chain for command and querybud

[JonasWijne]

Is there an existing issue that is already proposing this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe it

I have a issue when i want to log all commands, lets say I have a few commands and I want to log all commands that are run for auditing.

Describe the solution you'd like

a middleware chain that can be registered onto the command or query bus.

middleware class and decorator to register (maybe with filters)

middleware class should have a handle method (like a command handler or queryhandler) that has 2 arguments
command/query and a next function

Teachability, documentation, adoption, migration strategy

small example

@Middleware()
export class LogMiddleware implements IMiddleware<any, any> {
    handle(command: ICommand, next: NextFunction): any {
        console.log(command);
        return next(command);
    }
}

What is the motivation / use case for changing the behavior?

this allows for adding functionality without changing behaviour.

[FredericEspiau]

For your information, you can already do it using the ExplorerService: https://github.com/nestjs/cqrs/blob/master/src/services/explorer.service.ts

[kamilmysliwiec]

I have a issue when i want to log all commands, lets say I have a few commands and I want to log all commands that are run for auditing.

You can attach a side-effect by subscribing to the CommandBus stream. Command cannot be mutated though (and that's the desired behavior).