._matchedRoute[Name] inconsistency with nested routes.

[ghost]

There seems to be an issue with nested routes and the values of matchedRoute and matchedRouteName. Using one router directly work as expected, but for nested routes added and controlled like below, then the values seem to stop at the parent and disregard the child.

node.js: 10.6.0
npm: 6.4.1
koa-router: 7.4.0
koa: 2.5.2

Code sample:

var routes = new Router();
var child = new Router();

routes.get(
  'index',
  '/',
  app.context.routes.backend.core.index()
);

child.get(
  'c_test',
  '/test/:demo',
  app.context.routes.backend.core.index()
);

routes.use( '/child', child.routes(), child.allowedMethods() );

app.use( routes.routes() );
app.use( routes.allowedMethods() );

Expected Behavior:

ctx.matchedRoute = /child/test/:demo
ctx.matchedRouteName = c_test

Actual Behavior:

ctx.matchedRoute = /child
ctx.matchedRouteName = undefined

Fun fact

You get a different result again if you initialize the router with a prefix

var child = new Router({
 prefix: 'child'
});

routes.use( '', child.routes(), child.allowedMethods() );

Yielding ctx.matchedRoute to be (.*). Not my use case scenario here, but tested it to see if it solved my problem, it did not, and unexpectedly, gave a completely different result.

[etaoins]

It looks like ctx.routerName will contain the name of the nested child route

[jcao219]

As a workaround, change this line:

routes.use( '/child', child.routes(), child.allowedMethods() );

to

routes.use( '/child', child.allowedMethods(), child.routes() );

[mirague]

@jcao219 That workaround doesn't work unfortunately.

[jcao219]

@mirague That's unfortunate.

IIRC The root cause of this issue is koa-router currently uses simply the last matching route as _matchedRoute. When you have multiple routes that match, it does not have a good way to figure out which route you consider the "matchedRoute". I don't know of a perfect solution to this, and although I did submit a best-effort PR #492 to fix it, that solution has problems of its own.

One possible option is to return an array of matchedRoutes and let the user decide which to use