net/http: Conflicts with pattern when using NewServeMux

[bentcoder]

Go version

go version go1.22.0 darwin/amd64

Output of go env in your module/workspace:

GO111MODULE='on'
GOARCH='amd64'
GOBIN=''
GOCACHE='/Users/me/Library/Caches/go-build'
GOENV='/Users/me/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/me/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/me/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/Cellar/go/1.22.0/libexec'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/Cellar/go/1.22.0/libexec/pkg/tool/darwin_amd64'
GOVCS=''
GOVERSION='go1.22.0'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='cc'
CXX='c++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/4d/gcwrbh1s0nz1xhvb6mbfsv840000gn/T/go-build3252772856=/tmp/go-build -gno-record-gcc-switches -fno-common'

What did you do?

package main

import (
	"net/http"
)

func main() {
	rtr := http.NewServeMux()
	rtr.HandleFunc("GET /users/{id}", func(w http.ResponseWriter, r *http.Request) { w.Write([]byte(`GET /users/{id}`)) })
	rtr.HandleFunc("GET /{ver}/users", func(w http.ResponseWriter, r *http.Request) { w.Write([]byte(`GET /{ver}/users`)) })

	http.ListenAndServe(":1234", rtr)
}

What did you see happen?

panic: pattern "GET /{ver}/users" (registered at /Users/me/dev/golang/mix/rest/main.go:10) conflicts with pattern "GET /users/{id}" (registered at /Users/me/dev/golang/mix/rest/main.go:9):
GET /{ver}/users and GET /users/{id} both match some paths, like "/users/users".
But neither is more specific than the other.
GET /{ver}/users matches "/ver/users", but GET /users/{id} doesn't.
GET /users/{id} matches "/users/id", but GET /{ver}/users doesn't.

goroutine 1 [running]:
net/http.(*ServeMux).register(...)
        /usr/local/Cellar/go/1.22.0/libexec/src/net/http/server.go:2733
net/http.(*ServeMux).HandleFunc(0xc00011ab60, {0x35d1977, 0x10}, 0x36cf208)
        /usr/local/Cellar/go/1.22.0/libexec/src/net/http/server.go:2707 +0xb2
main.main()
        /Users/me/dev/golang/mix/rest/main.go:10 +0xad
exit status 2

What did you expect to see?

I expected this routing setup to work because routes below are not same. The {ver} is a dynamic hence adjustable by client.

GET /users/111
GET /users/222

GET /aaa/users
GET /bbb/users
GET /ccc/users

[seankhliao]

/users/users would match both, so the pattern isn't allowed

Closing as working as intended

[gabyhelp]

Related Issues and Documentation

• net/http: ServeMux behaves inconsistently across operating systems #66288 (closed)
• net/http: precedence in dynamic urls doesn't work as expected when using http.ServeMux #68030 (closed)
• net/http: enhanced ServerMux routing #65231 (closed)
• net/http: 301 instead of 404 for unmatched requests #65624 (closed)
• net/http: infinite redirect on path variable followed by trailing slash #67657 (closed)
• net/http: muxer no longer redirects host patterns in go1.10 #23183 (closed)
• expvar: creates conflict with "GET /" route #65723 (closed)
• net/http: reuse ServerMux to match PathValues using radix #63682 (closed)
• net/http: document and test behavior of ServeMux with ports #23351 (closed)
• net/http ServeMux Wildcard No Compilation Error When Using * and No Documentation on * #68676 (closed)

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