client: Add dial option to disable global dial options (#6016)

clientconn.go

@@ -146,8 +146,18 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 	cc.safeConfigSelector.UpdateConfigSelector(&defaultConfigSelector{nil})
 	cc.ctx, cc.cancel = context.WithCancel(context.Background())
 
-	for _, opt := range globalDialOptions {
-		opt.apply(&cc.dopts)
+	disableGlobalOpts := false
+	for _, opt := range opts {
+		if _, ok := opt.(*disableGlobalDialOptions); ok {
+			disableGlobalOpts = true
+			break
+		}
+	}
+
+	if !disableGlobalOpts {
+		for _, opt := range globalDialOptions {
+			opt.apply(&cc.dopts)
+		}
 	}
 
 	for _, opt := range opts {

default_dial_option_server_option_test.go

@@ -19,6 +19,7 @@
 package grpc
 
 import (
+	"fmt"
 	"strings"
 	"testing"
 
@@ -58,6 +59,21 @@ func (s) TestAddGlobalDialOptions(t *testing.T) {
 	}
 }
 
+// TestDisableGlobalOptions tests dialing with the disableGlobalDialOptions dial
+// option. Dialing with this set should not pick up global options.
+func (s) TestDisableGlobalOptions(t *testing.T) {
+	// Set transport credentials as a global option.
+	internal.AddGlobalDialOptions.(func(opt ...DialOption))(WithTransportCredentials(insecure.NewCredentials()))
+	// Dial with the disable global options dial option. This dial should fail
+	// due to the global dial options with credentials not being picked up due
+	// to global options being disabled.
+	noTSecStr := "no transport security set"
+	if _, err := Dial("fake", internal.DisableGlobalDialOptions.(func() DialOption)()); !strings.Contains(fmt.Sprint(err), noTSecStr) {
+		t.Fatalf("Dialing received unexpected error: %v, want error containing \"%v\"", err, noTSecStr)
+	}
+	internal.ClearGlobalDialOptions()
+}
+
 func (s) TestAddGlobalServerOptions(t *testing.T) {
 	const maxRecvSize = 998765
 	// Set and check the ServerOptions

dialoptions.go

@@ -45,6 +45,7 @@ func init() {
 	}
 	internal.WithBinaryLogger = withBinaryLogger
 	internal.JoinDialOptions = newJoinDialOption
+	internal.DisableGlobalDialOptions = newDisableGlobalDialOptions
 }
 
 // dialOptions configure a Dial call. dialOptions are set by the DialOption
@@ -96,6 +97,16 @@ type EmptyDialOption struct{}
 
 func (EmptyDialOption) apply(*dialOptions) {}
 
+type disableGlobalDialOptions struct{}
+
+func (disableGlobalDialOptions) apply(*dialOptions) {}
+
+// newDisableGlobalDialOptions returns a DialOption that prevents the ClientConn
+// from applying the global DialOptions (set via AddGlobalDialOptions).
+func newDisableGlobalDialOptions() DialOption {
+	return &disableGlobalDialOptions{}
+}
+
 // funcDialOption wraps a function that modifies dialOptions into an
 // implementation of the DialOption interface.
 type funcDialOption struct {

internal/internal.go

@@ -77,6 +77,10 @@ var (
 	// globally for newly created client channels. The priority will be: 1.
 	// user-provided; 2. this method; 3. default values.
 	AddGlobalDialOptions interface{} // func(opt ...DialOption)
+	// DisableGlobalDialOptions returns a DialOption that prevents the
+	// ClientConn from applying the global DialOptions (set via
+	// AddGlobalDialOptions).
+	DisableGlobalDialOptions interface{} // func() grpc.DialOption
 	// ClearGlobalDialOptions clears the array of extra DialOption. This
 	// method is useful in testing and benchmarking.
 	ClearGlobalDialOptions func()