exporter: silently skip unpacking unknown reference

Signed-off-by: Justin Chadwell <[email protected]>

Author: jedevc

exporter/containerimage/export.go

@@ -349,6 +349,13 @@ func (e *imageExporterInstance) pushImage(ctx context.Context, src *exporter.Sou
 }
 
 func (e *imageExporterInstance) unpackImage(ctx context.Context, img images.Image, src *exporter.Source, s session.Group) (err0 error) {
+	p := platforms.Normalize(platforms.DefaultSpec())
+	ref, ok := src.FindRef(platforms.Format(p))
+	if !ok || ref == nil {
+		// platform ref not found, or found platform ref has no layers, so nothing to unpack
+		return nil
+	}
+
 	unpackDone := progress.OneOff(ctx, "unpacking to "+img.Name)
 	defer func() {
 		unpackDone(err0)
@@ -366,15 +373,6 @@ func (e *imageExporterInstance) unpackImage(ctx context.Context, img images.Imag
 		return err
 	}
 
-	ref, ok := src.FindRef(defaultPlatform())
-	if !ok {
-		return errors.Errorf("no reference for default platform %s", defaultPlatform())
-	}
-	if ref == nil {
-		// ref has no layers, so nothing to unpack
-		return nil
-	}
-
 	remotes, err := ref.GetRemotes(ctx, true, e.opts.RefCfg, false, s)
 	if err != nil {
 		return err
@@ -448,12 +446,6 @@ func addAnnotations(m map[digest.Digest]map[string]string, desc ocispecs.Descrip
 	}
 }
 
-func defaultPlatform() string {
-	// Use normalized platform string to avoid the mismatch with platform options which
-	// are normalized using platforms.Normalize()
-	return platforms.Format(platforms.Normalize(platforms.DefaultSpec()))
-}
-
 func NewDescriptorReference(desc ocispecs.Descriptor, release func(context.Context) error) exporter.DescriptorReference {
 	return &descriptorReference{
 		desc:    desc,