Feature request: support optional rewrites

[KnisterPeter]

I would need something like optiona/conditional rewrites. That could be similar as the spa conditionals --spa.asset-test-fs by checking if a file is available in the fs, then serve it, otherwise rewrite the request.

[75lb]

I'm not clear what you are asking me to do..

Maybe you could demonstrate what you are looking for with a simple middleware example. Please have a play with creating a simple middleware module: https://github.com/lwsjs/local-web-server/wiki/Creating-middleware.

[KnisterPeter]

This is it:

const Rewrite = require('lws-rewrite');
const path = require('path');
const fs = require('fs');

class ConditionalRewrite {
  constructor() {
    this.rewrite = new Rewrite();
  }

  optionDefinitions() {
    return this.rewrite.optionDefinitions();
  }

  middleware(options, lws) {
    const middlewares = this.rewrite.middleware(options, lws);
    const directory = path.resolve(options.directory);

    return middlewares.map((middleware) => {
      return async (ctx, next) => {
        const { url } = ctx.request;
        const fullPath = path.join(directory, url);

        try {
          const stats = await fs.promises.stat(fullPath);
          if (stats.isFile()) {
            return next();
          }
        } catch {
          //
        }
        return middleware(ctx, next);
      };
    });
  }
}

module.exports = ConditionalRewrite;

So basically, if a file is at the requested static location serve that and do not rewrite the request to something else.

[75lb]

I see, thanks.. This would introduce an I/O performance cost since it touches the filesystem for every incoming request.. this cost would be noticeable for users building an SPA (which involves a lot of URLs which do not map to the filesystem, e.g. /user/3 etc) since this middleware would try to find /user/3 and every other URL on the filesystem before responding..

It's not something I would consider adding to the default stack (unless there's genuine demand for it) but feel free to publish and share this middleware plugin so others can use it, if required.