@loopback/rest RestBindings.Http.request is returning an empty query variable

Question

I've been working with the early versions of the Loopback v4 package for quite some time, and the RestBindings.Http.Request binding has been working well until one of the most recent upgrades (not quite sure when it happened).

I'm still able to get values for most properties, but not the query property. Even with the most basic project, using the default ping controller, the query property is still empty. Below is a sample of my code, my query and the response:

import { Request, RestBindings, get, ResponseObject } from '@loopback/rest';
import { inject } from '@loopback/context';

export class PingController {
  constructor(@inject(RestBindings.Http.REQUEST) private req: Request) { }

  // Map to `GET /ping`
  @get('/ping')
  ping(): object {
    // Reply with a greeting, the current time, the url, and request headers
    return {
      query: 'Query response: ' + this.req.query.start,
      greeting: 'Hello from LoopBack',
      date: new Date(),
      url: this.req.url,
      headers: Object.assign({}, this.req.headers),
    };
  }
}

Query: localhost:3000/ping?start=2018-08-25&end=2018-09-09&user=larsm

Output:

    {   
   "query": "Query response: undefined",   
   "greeting": "Hello from LoopBack",   
   "date": "2018-11-27T23:21:53.142Z",   
   "url": "/ping?start=2018-08-25&end=2018-09-09&user=larsm",   
   "headers": {
        "host": "localhost:3000",
        "connection": "keep-alive",
        "cache-control": "max-age=0",
        "upgrade-insecure-requests": "1",
        "user-agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36",
        "accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8",
        "accept-encoding": "gzip, deflate, br",
        "accept-language": "nb-NO,nb;q=0.9,en-GB;q=0.8,en;q=0.7,no;q=0.6,nn;q=0.5,en-US;q=0.4"   } }

Answer 1

So I figured out that the above issues is caused by an intentional change in the @loopback/rest library, that is only processing query parameters that are pre-defined.

This means that you need to define them specifically in your controller, e.g. like this simple example:

  @get('/larsm')
  greet(
    @param.query.string('start') start: string,
    @param.query.string('end') end: string,
    @param.query.string('name') name: string,
  ) {
    return 'start: ' + start + ', end: ' + end + ', name: ' + name;
  }
}

Since there are several use cases where this is not always ideal, I did raise an issue with the Loopback team, and it looks like they have decided to revert the most recent change.

Answer 2

This problem will be fixed in the next release, see https://github.com/strongloop/loopback-next/pull/2089