move initializers to wasip1/net_wasip1.go

Signed-off-by: Achille Roussel <[email protected]>

Author: achille-roussel

wasip1/dial_wasip1.go

@@ -3,18 +3,11 @@ package wasip1
 import (
 	"context"
 	"net"
-	"net/http"
 	"os"
 
 	"github.com/stealthrocket/net/internal/syscall"
 )
 
-func init() {
-	if t, ok := http.DefaultTransport.(*http.Transport); ok {
-		t.DialContext = DialContext
-	}
-}
-
 // Dial connects to the address on the named network.
 func Dial(network, address string) (net.Conn, error) {
 	addr, err := lookupAddr("dial", network, address)

wasip1/net_wasip1.go

@@ -0,0 +1,46 @@
+package wasip1
+
+import (
+	"context"
+	"errors"
+	"net"
+	"net/http"
+)
+
+func dialResolverNotSupported(ctx context.Context, network, address string) (net.Conn, error) {
+	// The net.Resolver type makes a call to net.DialUDP to determine which
+	// resolved addresses are reachable, which does not go through its Dial
+	// hook. As a result, it is unusable on GOOS=wasip1 because it fails
+	// even when the Dial function is set because WASI preview 1 does not
+	// have a mechanism for opening UDP sockets.
+	//
+	// Instead of having (often indirect) use of the net.Resolver crash, we
+	// override the Dial function to error earlier in the resolver lifecycle
+	// with an error which is more explicit to the end user.
+	return nil, errors.New("net.Resolver not supported on GOOS=wasip1")
+}
+
+func init() {
+	net.DefaultResolver.Dial = dialResolverNotSupported
+
+	if t, ok := http.DefaultTransport.(*http.Transport); ok {
+		t.DialContext = DialContext
+	}
+}
+
+func newOpError(op string, addr net.Addr, err error) error {
+	return &net.OpError{
+		Op:   op,
+		Net:  addr.Network(),
+		Addr: addr,
+		Err:  err,
+	}
+}
+
+type netAddr struct {
+	network string
+	address string
+}
+
+func (na *netAddr) Network() string { return na.address }
+func (na *netAddr) String() string  { return na.address }