Debugging an error when using koa-router module that multiple routes were invoked on a single HTTP request:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

var app = require('koa')();
var router = require('koa-router')();
router.use(function *(next) {
  this.body = {};
  yield next;
});
router.get('/users', function *(next) {
  this.body['/users'] = true;
  yield next;
});
router.get('/users/:id?', function *(next) {
  this.body['/users/:id?'] = true;
  yield next;
});
app.use(router.routes());
app.listen(3000);

When making a request to get a list of users, it will match both routes:

1
2
3
4
5
6
7
8
9
10

$ http :3000/users
HTTP/1.1 200 OK
Connection: keep-alive
Content-Length: 34
Content-Type: application/json; charset=utf-8
{
    "/users": true,
    "/users/:id?": true
}

Because in the second route :id is optional, and since there is yield next statement in the first route, the second route will be executed subsequently.

The cause of the bug is the design of the routing GET /users/:id?. The correct routes are:

• GET /users: Retrieve a list (array) of users.
• GET /users/:id: Retrieve a single user object.

The question mark should not be appended to the end of id parameter, which effectively marking the route to perform both duties. It’s better to keep them simple and keep them separated.

Koa Router v4.2 does not support an array of middleware, multiple middleware must be entered one by one:

1

app.get('/foo', middleware1, middleware2);

Using an array is much cleaner than multiple arguments.

1

app.get('/foo', [middleware1, middleware2]);

But the above will throw error:

1

Error: GET: `middleware` must be a function, not `object`

This can be easily fixed by using Koa Compose:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

var app = require('koa')();
var router = require('koa-router');
var compose = require('koa-compose');
app.use(router(app));
app.get('/foo', compose([
  function *(next) {
    this.body = {};
    yield next;
  },
  function *(next) {
    this.body.foo = 'foo';
    yield next;
  },
  function *(next) {
    this.body.bar = 'bar';
    yield next;
  }
]));

Hence:

1

app.get('/foo', compose([middleware1, middleware2]));