grpc: optional interface to provide channel authority

clientconn.go

@@ -1981,16 +1981,14 @@ func (cc *ClientConn) determineAuthority() error {
 	}
 
 	endpoint := cc.parsedTarget.Endpoint()
-	target := cc.target
+	auth, isAuthOverrider := any(cc.resolverBuilder).(resolver.AuthorityOverrider)
 	switch {
 	case authorityFromDialOption != "":
 		cc.authority = authorityFromDialOption
 	case authorityFromCreds != "":
 		cc.authority = authorityFromCreds
-	case strings.HasPrefix(target, "unix:") || strings.HasPrefix(target, "unix-abstract:"):
-		// TODO: remove when the unix resolver implements optional interface to
-		// return channel authority.
-		cc.authority = "localhost"
+	case isAuthOverrider:
+		cc.authority = auth.GetServiceAuthority(cc.parsedTarget)
 	case strings.HasPrefix(endpoint, ":"):
 		cc.authority = "localhost" + endpoint
 	default:

internal/resolver/unix/unix.go

@@ -61,6 +61,10 @@ func (b *builder) Scheme() string {
 	return b.scheme
 }
 
+func (b *builder) GetServiceAuthority(t resolver.Target) string {
+	return "localhost"
+}
+
 type nopResolver struct {
 }
 

resolver/resolver.go

@@ -319,3 +319,12 @@ type Resolver interface {
 	// Close closes the resolver.
 	Close()
 }
+
+// AuthorityOverrider is implemented by Builders that wish to override the
+// default authority for the ClientConn.
+// By default, the authority used is target.Endpoint()
+type AuthorityOverrider interface {
+	// GetServiceAuthority returns the authority to use for a ClientConn with the
+	// given target. It must not perform I/O or any other blocking operations.
+	GetServiceAuthority(t Target) string
+}