imagetools: refactor combining repository logic

This patch modifies the existing combining code in imagetools create to
provide better support for multiple repositories down the road.
Specifically, the code should no longer rely on a single repository
being used for all sources and tags, and should resolve descriptors in
their relevant repositories.

Signed-off-by: Justin Chadwell <me@jedevc.com>

build/build.go

@@ -925,7 +925,21 @@ func BuildWithResultHandler(ctx context.Context, drivers []DriverInfo, opt map[s
 
 							itpull := imagetools.New(imageopt)
 
-							dt, desc, err := itpull.Combine(ctx, names[0], descs)
+							ref, err := reference.ParseNormalizedNamed(names[0])
+							if err != nil {
+								return err
+							}
+							ref = reference.TagNameOnly(ref)
+
+							srcs := make([]*imagetools.Source, len(descs))
+							for i, desc := range descs {
+								srcs[i] = &imagetools.Source{
+									Desc: desc,
+									Ref:  ref,
+								}
+							}
+
+							dt, desc, err := itpull.Combine(ctx, srcs)
 							if err != nil {
 								return err
 							}

commands/imagetools/create.go

@@ -82,14 +82,20 @@ func runCreate(dockerCli command.Cli, in createOptions, args []string) error {
 		return errors.Errorf("multiple repositories currently not supported, found %v", repos)
 	}
 
-	var repo string
-	for r := range repos {
-		repo = r
+	var defaultRepo *string
+	if len(repos) == 1 {
+		for repo := range repos {
+			defaultRepo = &repo
+		}
 	}
 
 	for i, s := range srcs {
 		if s.Ref == nil && s.Desc.MediaType == "" && s.Desc.Digest != "" {
-			n, err := reference.ParseNormalizedNamed(repo)
+			if defaultRepo == nil {
+				return errors.Errorf("multiple repositories specified, cannot determine default from %v", repos)
+			}
+
+			n, err := reference.ParseNormalizedNamed(*defaultRepo)
 			if err != nil {
 				return err
 			}
@@ -143,7 +149,6 @@ func runCreate(dockerCli command.Cli, in createOptions, args []string) error {
 					if err != nil {
 						return err
 					}
-					srcs[i].Ref = nil
 					if srcs[i].Desc.Digest == "" {
 						srcs[i].Desc = desc
 					} else {
@@ -162,12 +167,7 @@ func runCreate(dockerCli command.Cli, in createOptions, args []string) error {
 		}
 	}
 
-	descs := make([]ocispec.Descriptor, len(srcs))
-	for i := range descs {
-		descs[i] = srcs[i].Desc
-	}
-
-	dt, desc, err := r.Combine(ctx, repo, descs)
+	dt, desc, err := r.Combine(ctx, srcs)
 	if err != nil {
 		return err
 	}
@@ -190,13 +190,8 @@ func runCreate(dockerCli command.Cli, in createOptions, args []string) error {
 	return nil
 }
 
-type src struct {
-	Desc ocispec.Descriptor
-	Ref  reference.Named
-}
-
-func parseSources(in []string) ([]*src, error) {
-	out := make([]*src, len(in))
+func parseSources(in []string) ([]*imagetools.Source, error) {
+	out := make([]*imagetools.Source, len(in))
 	for i, in := range in {
 		s, err := parseSource(in)
 		if err != nil {
@@ -219,11 +214,11 @@ func parseRefs(in []string) ([]reference.Named, error) {
 	return refs, nil
 }
 
-func parseSource(in string) (*src, error) {
+func parseSource(in string) (*imagetools.Source, error) {
 	// source can be a digest, reference or a descriptor JSON
 	dgst, err := digest.Parse(in)
 	if err == nil {
-		return &src{
+		return &imagetools.Source{
 			Desc: ocispec.Descriptor{
 				Digest: dgst,
 			},
@@ -234,14 +229,14 @@ func parseSource(in string) (*src, error) {
 
 	ref, err := reference.ParseNormalizedNamed(in)
 	if err == nil {
-		return &src{
+		return &imagetools.Source{
 			Ref: ref,
 		}, nil
 	} else if !strings.HasPrefix(in, "{") {
 		return nil, err
 	}
 
-	var s src
+	var s imagetools.Source
 	if err := json.Unmarshal([]byte(in), &s.Desc); err != nil {
 		return nil, errors.WithStack(err)
 	}

util/imagetools/create.go

@@ -17,46 +17,46 @@ import (
 	"golang.org/x/sync/errgroup"
 )
 
-func (r *Resolver) Combine(ctx context.Context, in string, descs []ocispec.Descriptor) ([]byte, ocispec.Descriptor, error) {
-	ref, err := parseRef(in)
-	if err != nil {
-		return nil, ocispec.Descriptor{}, err
-	}
+type Source struct {
+	Desc ocispec.Descriptor
+	Ref  reference.Named
+}
 
+func (r *Resolver) Combine(ctx context.Context, srcs []*Source) ([]byte, ocispec.Descriptor, error) {
 	eg, ctx := errgroup.WithContext(ctx)
 
-	dts := make([][]byte, len(descs))
+	dts := make([][]byte, len(srcs))
 	for i := range dts {
 		func(i int) {
 			eg.Go(func() error {
-				dt, err := r.GetDescriptor(ctx, ref.String(), descs[i])
+				dt, err := r.GetDescriptor(ctx, srcs[i].Ref.String(), srcs[i].Desc)
 				if err != nil {
 					return err
 				}
 				dts[i] = dt
 
-				if descs[i].MediaType == "" {
+				if srcs[i].Desc.MediaType == "" {
 					mt, err := detectMediaType(dt)
 					if err != nil {
 						return err
 					}
-					descs[i].MediaType = mt
+					srcs[i].Desc.MediaType = mt
 				}
 
-				mt := descs[i].MediaType
+				mt := srcs[i].Desc.MediaType
 
 				switch mt {
 				case images.MediaTypeDockerSchema2Manifest, ocispec.MediaTypeImageManifest:
-					p := descs[i].Platform
-					if descs[i].Platform == nil {
+					p := srcs[i].Desc.Platform
+					if srcs[i].Desc.Platform == nil {
 						p = &ocispec.Platform{}
 					}
 					if p.OS == "" || p.Architecture == "" {
-						if err := r.loadPlatform(ctx, p, in, dt); err != nil {
+						if err := r.loadPlatform(ctx, p, srcs[i].Ref.String(), dt); err != nil {
 							return err
 						}
 					}
-					descs[i].Platform = p
+					srcs[i].Desc.Platform = p
 				case images.MediaTypeDockerSchema1Manifest:
 					return errors.Errorf("schema1 manifests are not allowed in manifest lists")
 				}
@@ -71,14 +71,14 @@ func (r *Resolver) Combine(ctx context.Context, in string, descs []ocispec.Descr
 	}
 
 	// on single source, return original bytes
-	if len(descs) == 1 {
-		if mt := descs[0].MediaType; mt == images.MediaTypeDockerSchema2ManifestList || mt == ocispec.MediaTypeImageIndex {
-			return dts[0], descs[0], nil
+	if len(srcs) == 1 {
+		if mt := srcs[0].Desc.MediaType; mt == images.MediaTypeDockerSchema2ManifestList || mt == ocispec.MediaTypeImageIndex {
+			return dts[0], srcs[0].Desc, nil
 		}
 	}
 
 	m := map[digest.Digest]int{}
-	newDescs := make([]ocispec.Descriptor, 0, len(descs))
+	newDescs := make([]ocispec.Descriptor, 0, len(srcs))
 
 	addDesc := func(d ocispec.Descriptor) {
 		idx, ok := m[d.Digest]
@@ -103,8 +103,8 @@ func (r *Resolver) Combine(ctx context.Context, in string, descs []ocispec.Descr
 		}
 	}
 
-	for i, desc := range descs {
-		switch desc.MediaType {
+	for i, src := range srcs {
+		switch src.Desc.MediaType {
 		case images.MediaTypeDockerSchema2ManifestList, ocispec.MediaTypeImageIndex:
 			var mfst ocispec.Index
 			if err := json.Unmarshal(dts[i], &mfst); err != nil {
@@ -114,7 +114,7 @@ func (r *Resolver) Combine(ctx context.Context, in string, descs []ocispec.Descr
 				addDesc(d)
 			}
 		default:
-			addDesc(desc)
+			addDesc(src.Desc)
 		}
 	}