platforms: provide simpler function for common use

cmd/ctr/utils.go

@@ -206,7 +206,7 @@ func getImageLayers(ctx gocontext.Context, image images.Image, cs content.Store)
 		return nil, errors.Wrap(err, "failed to unmarshal manifest")
 	}
 
-	diffIDs, err := image.RootFS(ctx, cs, platforms.Format(platforms.Default()))
+	diffIDs, err := image.RootFS(ctx, cs, platforms.Default())
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to resolve rootfs")
 	}

container_opts.go

@@ -80,7 +80,7 @@ func WithSnapshot(id string) NewContainerOpts {
 // root filesystem in read-write mode
 func WithNewSnapshot(id string, i Image) NewContainerOpts {
 	return func(ctx context.Context, client *Client, c *containers.Container) error {
-		diffIDs, err := i.(*image).i.RootFS(ctx, client.ContentStore(), platforms.Format(platforms.Default()))
+		diffIDs, err := i.(*image).i.RootFS(ctx, client.ContentStore(), platforms.Default())
 		if err != nil {
 			return err
 		}
@@ -109,7 +109,7 @@ func WithSnapshotCleanup(ctx context.Context, client *Client, c containers.Conta
 // root filesystem in read-only mode
 func WithNewSnapshotView(id string, i Image) NewContainerOpts {
 	return func(ctx context.Context, client *Client, c *containers.Container) error {
-		diffIDs, err := i.(*image).i.RootFS(ctx, client.ContentStore(), platforms.Format(platforms.Default()))
+		diffIDs, err := i.(*image).i.RootFS(ctx, client.ContentStore(), platforms.Default())
 		if err != nil {
 			return err
 		}

container_opts_unix.go

@@ -39,7 +39,7 @@ func WithCheckpoint(desc v1.Descriptor, snapshotKey string) NewContainerOpts {
 				fk := m
 				rw = &fk
 			case images.MediaTypeDockerSchema2Manifest:
-				config, err := images.Config(ctx, store, m, platforms.Format(platforms.Default()))
+				config, err := images.Config(ctx, store, m, platforms.Default())
 				if err != nil {
 					return err
 				}

image.go

@@ -45,7 +45,7 @@ func (i *image) Target() ocispec.Descriptor {
 
 func (i *image) RootFS(ctx context.Context) ([]digest.Digest, error) {
 	provider := i.client.ContentStore()
-	return i.i.RootFS(ctx, provider, platforms.Format(platforms.Default()))
+	return i.i.RootFS(ctx, provider, platforms.Default())
 }
 
 func (i *image) Size(ctx context.Context) (int64, error) {
@@ -55,11 +55,11 @@ func (i *image) Size(ctx context.Context) (int64, error) {
 
 func (i *image) Config(ctx context.Context) (ocispec.Descriptor, error) {
 	provider := i.client.ContentStore()
-	return i.i.Config(ctx, provider, platforms.Format(platforms.Default()))
+	return i.i.Config(ctx, provider, platforms.Default())
 }
 
 func (i *image) Unpack(ctx context.Context, snapshotterName string) error {
-	layers, err := i.getLayers(ctx, platforms.Format(platforms.Default()))
+	layers, err := i.getLayers(ctx, platforms.Default())
 	if err != nil {
 		return err
 	}

platforms/defaults.go

@@ -6,8 +6,13 @@ import (
 	specs "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
-// Default returns the current platform's default platform specification.
-func Default() specs.Platform {
+// Default returns the default specifier for the platform.
+func Default() string {
+	return Format(DefaultSpec())
+}
+
+// DefaultSpec returns the current platform's default platform specification.
+func DefaultSpec() specs.Platform {
 	return specs.Platform{
 		OS:           runtime.GOOS,
 		Architecture: runtime.GOARCH,

platforms/defaults_test.go

@@ -13,8 +13,13 @@ func TestDefault(t *testing.T) {
 		OS:           runtime.GOOS,
 		Architecture: runtime.GOARCH,
 	}
-	p := Default()
+	p := DefaultSpec()
 	if !reflect.DeepEqual(p, expected) {
 		t.Fatalf("default platform not as expected: %#v != %#v", p, expected)
 	}
+
+	s := Default()
+	if s != Format(p) {
+		t.Fatalf("default specifier should match formatted default spec: %v != %v", s, p)
+	}
 }

spec_opts_unix.go

@@ -73,7 +73,7 @@ func WithImageConfig(i Image) SpecOpts {
 			image = i.(*image)
 			store = client.ContentStore()
 		)
-		ic, err := image.i.Config(ctx, store, platforms.Format(platforms.Default()))
+		ic, err := image.i.Config(ctx, store, platforms.Default())
 		if err != nil {
 			return err
 		}
@@ -236,7 +236,7 @@ func WithRemappedSnapshotView(id string, i Image, uid, gid uint32) NewContainerO
 
 func withRemappedSnapshotBase(id string, i Image, uid, gid uint32, readonly bool) NewContainerOpts {
 	return func(ctx context.Context, client *Client, c *containers.Container) error {
-		diffIDs, err := i.(*image).i.RootFS(ctx, client.ContentStore(), platforms.Format(platforms.Default()))
+		diffIDs, err := i.(*image).i.RootFS(ctx, client.ContentStore(), platforms.Default())
 		if err != nil {
 			return err
 		}

spec_opts_windows.go

@@ -21,7 +21,7 @@ func WithImageConfig(i Image) SpecOpts {
 			image = i.(*image)
 			store = client.ContentStore()
 		)
-		ic, err := image.i.Config(ctx, store, platforms.Format(platforms.Default()))
+		ic, err := image.i.Config(ctx, store, platforms.Default())
 		if err != nil {
 			return err
 		}