Ability to extend the Stimulus Application class

[lb-]

Summary

Class inheritance provides a way to achieve custom behaviour and it would be great to also allow this at the Application level.

Currently, it is not easy to extend and use the Application class without rewriting its static start method.

Details

In the Application code, the start static method references the Application class directly instead of using this.

stimulus/src/core/application.ts

Lines 19 to 23 in f690a6a

	static start(element?: Element, schema?: Schema): Application {
	const application = new Application(element, schema)
	application.start()
	return application
	}

This means that even if you extend the Application with say a custom method override of load, this custom method will never get used.

Proposal

Using this instead of Application should solve the issue.

  static start(element?: Element, schema?: Schema): Application {
    const application = new this(element, schema)
    application.start()
    return application
  }

Use case

A trivial use case to add extra behaviour to the application stop call.

class MyApplication extends Application {
  stop() {
    super();
    console.log('application stopped');
  }
}

const application= MyApplication.start();
application.stop();

[marcoroth]

Hey @lb-, thanks for opening this issue.

I think your proposal makes sense and we could implement this. Feel free to open a pull request for it! Thank you!

[lb-]

Thanks @marcoroth - should this be documented anywhere? Or is it best left undocumented?

I would assume we would add a section around the application debugging or before the application error callback section?

https://stimulus.hotwired.dev/handbook/installing#debugging

[marcoroth]

I would probably have left it undocumented, since it's technically "just" regular class inheritance at work. But I wouldn't be opposed to having a small note/example in the documentation for it.

[lb-]

Thanks. I still have this on my radar and hope to get a PR up when I get the chance.

[lb-]

PR up #603