build: fail early if trying to export index annotations with moby exporter

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>

build/build.go

@@ -93,6 +93,7 @@ type Options struct {
 	ProvenanceResponseMode confutil.MetadataProvenanceMode
 	SourcePolicy           *spb.Policy
 	GroupRef               string
+	Annotations            map[exptypes.AnnotationKey]string // Not used during build, annotations are already set in Exports. Just used to check for support with drivers.
 }
 
 type CallFunc struct {

build/opt.go

@@ -28,6 +28,7 @@ import (
 	"github.com/moby/buildkit/client"
 	"github.com/moby/buildkit/client/llb"
 	"github.com/moby/buildkit/client/ociindex"
+	"github.com/moby/buildkit/exporter/containerimage/exptypes"
 	gateway "github.com/moby/buildkit/frontend/gateway/client"
 	"github.com/moby/buildkit/identity"
 	"github.com/moby/buildkit/session"
@@ -180,6 +181,20 @@ func toSolveOpt(ctx context.Context, node builder.Node, multiDriver bool, opt *O
 		}
 	}
 
+	// check if index annotations are supported by docker driver
+	if len(opt.Exports) > 0 && opt.CallFunc == nil && len(opt.Annotations) > 0 && nodeDriver.IsMobyDriver() && !nodeDriver.Features(ctx)[driver.MultiPlatform] {
+		for _, exp := range opt.Exports {
+			if exp.Type == "image" || exp.Type == "docker" {
+				for ak := range opt.Annotations {
+					switch ak.Type {
+					case exptypes.AnnotationIndex, exptypes.AnnotationIndexDescriptor:
+						return nil, nil, errors.New("index annotations not supported for single platform export")
+					}
+				}
+			}
+		}
+	}
+
 	// fill in image exporter names from tags
 	if len(opt.Tags) > 0 {
 		tags := make([]string, len(opt.Tags))