`webrtc` transport breaks compilation for WASM even if it not specified in transports

[v1rtl]

Currently if you try to compile the most basic libp2p host with 0 transports and no listeners like this:

package main

import (
	"log"

	"github.com/libp2p/go-libp2p"
	"github.com/libp2p/go-libp2p/core/crypto"
	"github.com/libp2p/go-libp2p/p2p/security/noise"
)

func main() {
	priv, _, err := crypto.GenerateKeyPair(
		crypto.Ed25519,
		-1,
	)
	if err != nil {
		panic(err)
	}

	if err != nil {
		panic(err)
	}
	h2, err := libp2p.NewWithoutDefaults(
		libp2p.Identity(priv),
		libp2p.NoListenAddrs,
		libp2p.Security(noise.ID, noise.New),
		libp2p.NoTransports,
	)
	if err != nil {
		panic(err)
	}
	defer h2.Close()
}

it will fail during compilation:

GOOS=js GOARCH=wasm go build
# github.com/libp2p/go-libp2p/p2p/transport/webrtc
/home/v1rtl/go/pkg/mod/github.com/libp2p/go-libp2p@v0.41.1/p2p/transport/webrtc/connection.go:109:12: pc.SCTP().OnClose undefined (type *webrtc.SCTPTransport has no field or method OnClose)
/home/v1rtl/go/pkg/mod/github.com/libp2p/go-libp2p@v0.41.1/p2p/transport/webrtc/listener.go:68:35: config.Certificates undefined (type webrtc.Configuration has no field or method Certificates)
/home/v1rtl/go/pkg/mod/github.com/libp2p/go-libp2p@v0.41.1/p2p/transport/webrtc/listener.go:199:40: unknown field LoggerFactory in struct literal of type webrtc.SettingEngine
/home/v1rtl/go/pkg/mod/github.com/libp2p/go-libp2p@v0.41.1/p2p/transport/webrtc/listener.go:200:16: settingEngine.SetAnsweringDTLSRole undefined (type webrtc.SettingEngine has no field or method SetAnsweringDTLSRole)
// ...

my guess is that it fails because webrtc transport is imported in multiple places (or maybe hust here) which breaks compilation:

/home/v1rtl/Coding/forks/go-libp2p/p2p/protocol/autonatv2/client.go:17: libp2pwebrtc "github.com/libp2p/go-libp2p/p2p/transport/webrtc"

[shoriwe]

I could find some things that may be useful for you @sukunrt.

Upstream

go-libp2p/p2p/transport/webrtc/connection.go

Line 109 in 72894e3

pc.SCTP().OnClose(func(err error) {

This line assumes all platforms including WASM have the same implementation of SCTPTransport, DTLSTransport and SettingEngine.

• In the case of SCTPTransport.

Non JS targets appear to have a full implementation of the expected interface.

While JS one only supports a small subsets of operations:

func (r *SCTPTransport) JSValue() js.Value
func (r *SCTPTransport) Transport() *DTLSTransport

• For DTLSTransport libp2p only needs GetRemoteCertificate which is missing on JS target

• SettingEngine is a bit more complex since libp2p's code depends on even more operations

libp2p

By guessing, I think it could be useful to check the default code included for libp2p clients. Maybe webrtc is included because the library things user may use of this transport to connect to other peers from within the browser.

Not limited to above sample

• Using New also fails.

h2, err := libp2p.New(
	libp2p.Identity(priv),
	libp2p.NoListenAddrs,
	libp2p.Security(noise.ID, noise.New),
	libp2p.NoTransports,
)

• Using only the identity also fails.

h2, err := libp2p.New(libp2p.Identity(priv))

Ideas.

Since webrtc is a must have since there are peers waiting for connections using this transport. Maybe the solution should not be disabled webrtc on WASM but rather target upstream?

@sukunrt Let me know how can I help.

[v1rtl]

There's a draft PR for constructing a host with fx options, makes the binary smaller and omits unused packages