net: Listen("tcp", "localhost:0") fails on js/wasm and wasip1/wasm #59718
Description
What version of Go are you using (go version)?
$ gotip version go version devel go1.21-0853f8ca Fri Apr 14 20:24:18 2023 +0000 linux/amd64
Does this issue reproduce with the latest release?
Yes.
What operating system and processor architecture are you using (go env)?
go env Output
$ gotip env GO111MODULE="" GOARCH="amd64" GOBIN="" GOCACHE="/usr/local/google/home/bcmills/.cache/go-build" GOENV="/usr/local/google/home/bcmills/.config/go/env" GOEXE="" GOEXPERIMENT="" GOFLAGS="" GOHOSTARCH="amd64" GOHOSTOS="linux" GOINSECURE="" GOMODCACHE="/tmp/tmp.GW5wdtYKZr/.gopath/pkg/mod" GONOPROXY="" GONOSUMDB="" GOOS="linux" GOPATH="/tmp/tmp.GW5wdtYKZr/.gopath" GOPRIVATE="" GOPROXY="https://proxy.golang.org,direct" GOROOT="/usr/local/google/home/bcmills/sdk/gotip" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/usr/local/google/home/bcmills/sdk/gotip/pkg/tool/linux_amd64" GOVCS="" GOVERSION="devel go1.21-0853f8ca Fri Apr 14 20:24:18 2023 +0000" GCCGO="/usr/bin/gccgo" GOAMD64="v1" AR="ar" CC="gcc" CXX="c++" CGO_ENABLED="1" GOMOD="/tmp/tmp.GW5wdtYKZr/go.mod" 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 -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build3341472864=/tmp/go-build -gno-record-gcc-switches"
What did you do?
Run the following program with GOOS=js GOARCH=wasm:
package main
import (
"fmt"
"net"
"os"
"golang.org/x/net/nettest"
)
func main() {
if !nettest.TestableNetwork("tcp") {
fmt.Println("tcp is not testable")
os.Exit(1)
}
if !nettest.TestableAddress("tcp", "localhost") {
fmt.Println("localhost is not testable on tcp")
os.Exit(1)
}
l, err := net.Listen("tcp", "localhost:0")
if err != nil {
panic(err)
}
fmt.Printf("listening on %s\n", l.Addr())
l.Close()
}What did you expect to see?
One of the “… is not testable“ messages, or a Listener address.
What did you see instead?
$ GOOS=js GOARCH=wasm go run .
panic: listen tcp: lookup localhost: Protocol not available
goroutine 1 [running]:
main.main()
/tmp/tmp.GW5wdtYKZr/main.go:22 +0x2a
exit status 2
Perhaps tellingly, net/conn_test.go claims:
// This file implements API tests across platforms and will never have a build
// tag.
but then:
//go:build !js && !wasip1
(introduced in CL 109995)
(attn @golang/wasm)