Echo: Route conflict

[mmindenhall]

Description

If I have two routes defined, one with a static value and one with a path param, the static value cannot be used as the path param even if the two routes do not have the same number of path segments.

For example, if I define these two routes:

GET /users/:id/comments   // 3 path segments
GET /:resourceName/:id    // 2 path segments

The second route fails when :resourceId is users (but works for any other value). I'm confused by this behavior. I know the matching order is static -> param -> any, but I would have thought that if no match was found down the static /users path, the router would then attempt to match down the /:resourceId path.

Checklist

• [x] Dependencies installed
• [x] No typos
• [x] Searched existing issues and docs

Expected behaviour

All of these requests should work:

GET /users/1/comments
GET /boozers/1
GET /users/1

Actual behaviour

These two work:

GET /users/1/comments
GET /boozers/1

But this fails:

GET /users/1

Steps to reproduce

Working code to debug

package main

import (
    "testing"

    "github.com/labstack/echo"
    "github.com/stretchr/testify/assert"
)

func TestRouteConflict(t *testing.T) {
    e := echo.New()
    r := e.Router()

    e.GET("/users/:id/comments", func(c echo.Context) error {
        c.Set("r", 1)
        return nil
    })

    e.GET("/:resourceName/:id", func(c echo.Context) error {
        c.Set("r", 2)
        return nil
    })

    c := e.NewContext(nil, nil)
    r.Find(echo.GET, "/users/1/comments", c)
    c.Handler()(c)
    assert.Equal(t, 1, c.Get("r"))

    c = e.NewContext(nil, nil)
    r.Find(echo.GET, "/boozers/1", c)
    c.Handler()(c)
    assert.Equal(t, 2, c.Get("r"))

    c = e.NewContext(nil, nil)
    r.Find(echo.GET, "/users/1", c)
    c.Handler()(c)
    assert.Equal(t, 2, c.Get("r")) // this assertion fails
}

Version/commit

3.1.0-rc1

[adred]

httprouter has this problem which is a radix tree based router also.

[mmindenhall]

Echo already does better than httprouter in this regard. From httprouter README:

For example you can not register the patterns /user/new and /user/:user for the same request method at the same time.

Echo uses the same patterns as a _working_ example on the Routing page of the guide:

e.GET("/users/:id", func(c echo.Context) error {
    return c.String(http.StatusOK, "/users/:id")
})

e.GET("/users/new", func(c echo.Context) error {
    return c.String(http.StatusOK, "/users/new")
})

e.GET("/users/1/files/*", func(c echo.Context) error {
    return c.String(http.StatusOK, "/users/1/files/*")
})

[abaehre]

The reason for this is the way the radix tree is created.
Running your test file the radix tree looks like such -

└── /, pnames=[] ppath= handler=&{<nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil>}
 ├── users/, pnames=[] ppath= handler=&{<nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil>}
 │ └── :, pnames=[id] ppath=/users/:id/comments handler=&{<nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil>}
 │  └── /comments, pnames=[id] ppath=/users/:id/comments handler=&{<nil> <nil> 0x135ff50 <nil> <nil> <nil> <nil> <nil> <nil> <nil>}
 └── :, pnames=[resourceName] ppath=/:resourceName/:id handler=&{<nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil>}
  └── /, pnames=[] ppath= handler=&{<nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil> <nil>}
   └── :, pnames=[resourceName id] ppath=/:resourceName/:id handler=&{<nil> <nil> 0x135ff50 <nil> <nil> <nil> <nil> <nil> <nil> <nil>}

your 3rd test hits on /users/: which has no handlers associated with it since you didn't actually create a handler for that path. It just happened to be an intermediate step in the creation of the tree.

I'm not sure if this is a limitation of the radix tree, or something specific to echo, but I figured I'd at least comment for those that see this in the future.

[stale[bot]]

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