Add a way to pass configuration into handler setup controllers

[aredridel]

As a vague example, maybe something like accepting functions in the form of

module.exports = function (router, config) {
}

This would solve one of the most common questions I get in the context of Kraken: "How do I handle configuration? I can't get to it from here"

[sixlettervariables]

+1 (I'd use this feature today)

[jasisk]

So the complexity here is that enrouten has no concept of config. Thinking this over, I think the simplest way to implement this would be to add another internal shortstop handler to confit—similar to the config handler—that would be replaced with a reference to the completely built config factory. That way, it could be passed as an argument (or option) to enrouten.

Just a thought.

[aredridel]

Yeah. Some sort of opaque thing passed in? If it's config, yay! when used by Kraken.

[totherik]

Yep, this is a long time coming but really is a form of DI. As I start contemplating I welcome any thoughts or ideas.

EDIT: And yes, I'll start digging into your suggestion @jasisk.

[totherik]

One thing that just occurred to me is that this will necessarily force a major version change (I was hoping it wouldn't). The current rule for directory mode is that the traversal mechanism will only initialize files that accept a single argument, allowing route definitions to be intermingled with other files. By having user-defined arguments the mechanism for identifying those files becomes much more murky.

[aredridel]

Oh, that is just unfortunate!

[totherik]

It may be a blessing in disguise. Gives us a little more latitude to take advantage of better directory layout and improve config. I've put together a very rough proposal if anyone has feedback.

[aredridel]

Aye. That seems like an awful lot of DI machinery and jargon to drag in, and it means that we're coupled to doing dependency injection our way, which just makes it unpleasant for people who have another opinion there.

[aredridel]

I see the intent, but something is rubbing me really wrong about it.

[totherik]

Yep, re: DI. I was considering using an existing implementation by default and injecting the router itself that way, but I haven't yet found a "lightweight" module, hence the code I put together. If we go through with this I'd prefer to defer to an existing module should we go in whole hog, and use it to manage all dependencies, including router.

[aredridel]

I dunno. It feels a lot like a lot of conceptual overhead to use an otherwise simple module.

[totherik]

I'm im not sure that simplicity and configurability are mutually exclusive. The request to inject arbitrary objects during initialization isn't the basic, simple use-case here. A smart default of always injecting the router will most certainly help.

[aredridel]

Indeed.

[grawk]

regarding the single argument function, just because a function signature has a single argument doesn't mean the function cannot be called with additional arguments

[totherik]

True, but I'm personally not willing to codifyvar myvar = arguments[1]; as a desired pattern. :)

[grawk]

What about attaching the config as a property of the router?

[jasisk]

That's interesting. We already provide a facade there.

[totherik]

Well attaching config explicitly so will create a tight coupling between kraken-js and enrouten, something that I'm trying to avoid. The only way to avoid that would be to support something like an additionalProperties config property that would be an object of arbitrary stuff which would get attached to the router instance.

With a design that supports multiple arguments the default case (just router) could possibly keep the current scanning mechanism, but when additional dependencies are configured to be injected it could switch into a more liberal scanning mode. That would preserve backward compat.

[grawk]

the single argument could be an object but the user would need to be aware of when they have triggered DI in order to pull the router argument apart

[pvenkatakrishnan]

+1 to adding additional params as a config

[totherik]

Does someone want to put together a proposal?

[grawk]

I don't have much time today and tomorrow. But if it's still dangling when I'm free I would like to take a crack at it.