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RFC: Decorator Based CLI Application Framework ​

Summary ​

This RFC proposes a decorator-based command line application framework that allows developers to define controllers and commands using decorators. The framework will support dependency injection, routing, and middlewares.

Building Blocks ​

Injectable Entity ​

An injectable entity is a class that can have dependencies injected into its constructor. For more details, see the Dependency Injection RFC.

Command ​

A command is an endpoint, method withing a controller that can be executed from the command line. Commands can have arguments and options. The return value of the command is the application exit code, where void is treated as 0.

Controller ​

A controller is an injectable class that can have dependencies injected into its constructor. Annotated with the @Controller decorator.

Controller can have a single main command or multiple sub-commands, but not both.

Module ​

A module is a container for controllers. The module is an injectable class that can have dependencies injected into its constructor and can register providers or import other modules. Annotated with the @Module decorator. The module is the dependency injection context of its controllers.

Implementation Details ​

Decorators will be used to define endpoints, controllers and modules. The decorators will be processed at runtime to set up middleware and error handling.

@Main() decorator ​

The @Main() decorator is used to define the main command of a controller. The main command is executed when the controller is invoked without any sub-command.

ts

@Controller()
class MyController {
    @Main()
    mainCommand() {
        console.log("Hello, World!");
    }
}

@Command() decorator ​

The @Command() decorator is used to define a sub-command of a controller. The sub-command is executed when the controller is invoked with the sub-command name.

ts

@Controller()
class MyController {
    @Command("greet")
    greetCommand() {
        console.log("Hello, World!");
    }

    @Command("farewell")
    farewellCommand() {
        console.log("Goodbye, World!");
    }
}