Inversion of Control for controllers

[koubas]

First, I'm glad that this project starts to show signs of life again, thanks! I'm pretty new to oas-tools and modern js/ts development. I don't miss a full blown DI containers and so on but I'm wondering, how do I achieve basic Inversion of Control for OAS Tools controllers? From all the examples I see it wants me to import the dependencies (services, configs, ...) in the controller module, but I want them to be injectable during creation so I can mock them in tests. Can this be achieved?

[alesancor1]

Unfortunately, DI is not possible in OAS Tools currently. However, since the framework is flexible enough, you could implement a basic DI that can serve your purpose. To do that, you need to create a new external module that replaces the router middleware and add it to the OAS Tools chain through oasTools.use( ). You could then inject your dependencies through this new module's configuration:

1. Create a new file for the new module and copy the router middleware code inside:

// newRouter.js
import { OASBase, errors, logger } from "@oas-tools/commons";
import { commons } from "../../utils/index.js";
import { pathToFileURL } from "url";

export class OASRouter extends OASBase {

  constructor(oasFile, middleware) {
    super(oasFile, middleware);
  }

  static async initialize(oasFile, config) {
    const controllers = await OASRouter.#loadControllers(oasFile, config);
    return new OASRouter(oasFile, (req, res, _next) => {  
      const requestPath = req.route.path;
      const method = req.method;
      controllers[requestPath][method](req, res);
    });
  }

...

2. Modify the call to controllers (line 16) to inject your dependencies inside its arguments:

// call controller
controllers[requestPath][method](req, res, config.di);

3. Modify your controllers to add the new argument

export function DIController(req, res, deps) {
    // Do something
}

4. Disable router in configuration and use this middleware instead at position 4 (after the response validation, see the docs here)

// .oastoolsrc
{
    ...
    "middleware": {
        "router": {
            "disable": true
        }
    }
}

import { NewRouter } from './newRouter.js';

const depsCfg= {
  di: {
     dep1: import('some-dependency',
     dep2: import('another-dependency') 
  }
}

oasTools.use(NewRouter, depsCfg, 4);
oasTools.initialize(app).then(() => ...)

I hope you find this workaround useful. There are many other ways to implement DI, like adding your dependencies to the req or res.locals objects to avoid modifying your controllers. Find the way that works better for you and feel free to leave a sugestion if you find a good implementation. This feature is interesting and I will possibly implement it in future versions 😄

[koubas]

tanks! Seems acceptable for now.