move moby check to driver interface

Driver caching masked the method detection

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

build/build.go

@@ -280,13 +280,6 @@ func toRepoOnly(in string) (string, error) {
 	return strings.Join(out, ","), nil
 }
 
-func isDefaultMobyDriver(d driver.Driver) bool {
-	_, ok := d.(interface {
-		IsDefaultMobyDriver()
-	})
-	return ok
-}
-
 func toSolveOpt(ctx context.Context, d driver.Driver, multiDriver bool, opt Options, pw progress.Writer, dl dockerLoadCallback) (solveOpt *client.SolveOpt, release func(), err error) {
 	defers := make([]func(), 0, 2)
 	releaseF := func() {
@@ -338,15 +331,11 @@ func toSolveOpt(ctx context.Context, d driver.Driver, multiDriver bool, opt Opti
 		so.FrontendAttrs["multi-platform"] = "true"
 	}
 
-	_, isDefaultMobyDriver := d.(interface {
-		IsDefaultMobyDriver()
-	})
-
 	switch len(opt.Exports) {
 	case 1:
 		// valid
 	case 0:
-		if isDefaultMobyDriver && !noDefaultLoad() {
+		if d.IsMobyDriver() && !noDefaultLoad() {
 			// backwards compat for docker driver only:
 			// this ensures the build results in a docker image.
 			opt.Exports = []client.ExportEntry{{Type: "image", Attrs: map[string]string{}}}
@@ -400,7 +389,7 @@ func toSolveOpt(ctx context.Context, d driver.Driver, multiDriver bool, opt Opti
 		}
 		if e.Type == "docker" {
 			if e.Output == nil {
-				if isDefaultMobyDriver {
+				if d.IsMobyDriver() {
 					e.Type = "image"
 				} else {
 					w, cancel, err := dl(e.Attrs["context"])
@@ -414,7 +403,7 @@ func toSolveOpt(ctx context.Context, d driver.Driver, multiDriver bool, opt Opti
 				return nil, nil, notSupported(d, driver.DockerExporter)
 			}
 		}
-		if e.Type == "image" && isDefaultMobyDriver {
+		if e.Type == "image" && d.IsMobyDriver() {
 			opt.Exports[i].Type = "moby"
 			if e.Attrs["push"] != "" {
 				if ok, _ := strconv.ParseBool(e.Attrs["push"]); ok {
@@ -493,7 +482,7 @@ func Build(ctx context.Context, drivers []DriverInfo, opt map[string]Options, do
 
 	var noMobyDriver driver.Driver
 	for _, d := range drivers {
-		if !isDefaultMobyDriver(d.Driver) {
+		if !d.Driver.IsMobyDriver() {
 			noMobyDriver = d.Driver
 			break
 		}

driver/docker-container/driver.go

@@ -32,6 +32,10 @@ type Driver struct {
 	env     []string
 }
 
+func (d *Driver) IsMobyDriver() bool {
+	return false
+}
+
 func (d *Driver) Bootstrap(ctx context.Context, l progress.Logger) error {
 	return progress.Wrap("[internal] booting buildkit", l, func(sub progress.SubLogger) error {
 		_, err := d.DockerAPI.ContainerInspect(ctx, d.Name)

driver/docker/driver.go

@@ -57,4 +57,6 @@ func (d *Driver) Factory() driver.Factory {
 	return d.factory
 }
 
-func (d *Driver) IsDefaultMobyDriver() {}
+func (d *Driver) IsMobyDriver() bool {
+	return true
+}

driver/driver.go

@@ -57,6 +57,7 @@ type Driver interface {
 	Rm(ctx context.Context, force bool) error
 	Client(ctx context.Context) (*client.Client, error)
 	Features() map[Feature]bool
+	IsMobyDriver() bool
 }
 
 func Boot(ctx context.Context, d Driver, pw progress.Writer) (*client.Client, error) {

driver/kubernetes/driver.go

@@ -44,6 +44,10 @@ type Driver struct {
 	podChooser       podchooser.PodChooser
 }
 
+func (d *Driver) IsMobyDriver() bool {
+	return false
+}
+
 func (d *Driver) Bootstrap(ctx context.Context, l progress.Logger) error {
 	return progress.Wrap("[internal] booting buildkit", l, func(sub progress.SubLogger) error {
 		_, err := d.deploymentClient.Get(ctx, d.deployment.Name, metav1.GetOptions{})