add Validate function

fakes/image.go

@@ -307,6 +307,10 @@ func (i *Image) Found() bool {
 	return !i.deleted
 }
 
+func (i *Image) Valid() bool {
+	return !i.deleted
+}
+
 func (i *Image) AnnotateRefName(refName string) error {
 	i.refName = refName
 	return nil

image.go

@@ -21,6 +21,8 @@ type Image interface {
 	Env(key string) (string, error)
 	// Found tells whether the image exists in the repository by `Name()`.
 	Found() bool
+	// Valid returns true if the image is well formed (e.g. all manifest layers exist on the registry).
+	Valid() bool
 	GetAnnotateRefName() (string, error)
 	// GetLayer retrieves layer by diff id. Returns a reader of the uncompressed contents of the layer.
 	GetLayer(diffID string) (io.ReadCloser, error)

layout/layout.go

@@ -87,6 +87,10 @@ func (i *Image) Found() bool {
 	return ImageExists(i.path)
 }
 
+func (i *Image) Valid() bool {
+	return i.Found()
+}
+
 func ImageExists(path string) bool {
 	if !pathExists(path) {
 		return false

layout/layout_test.go

@@ -912,6 +912,53 @@ func testImage(t *testing.T, when spec.G, it spec.S) {
 		})
 	})
 
+	when("#Valid", func() {
+		var image *layout.Image
+
+		it.Before(func() {
+			imagePath = filepath.Join(tmpDir, "found-image")
+			image, err = layout.NewImage(imagePath)
+			h.AssertNil(t, err)
+		})
+
+		it.After(func() {
+			os.RemoveAll(imagePath)
+		})
+
+		when("image doesn't exist on disk", func() {
+			it.Before(func() {
+				imagePath = filepath.Join(tmpDir, "non-exist-image")
+				image, err = layout.NewImage(imagePath)
+				h.AssertNil(t, err)
+			})
+
+			it("returns false", func() {
+				h.AssertTrue(t, func() bool {
+					return !image.Found()
+				})
+			})
+		})
+
+		when("image exists on disk", func() {
+			it.Before(func() {
+				imagePath = filepath.Join(testDataDir, "my-previous-image")
+				image, err = layout.NewImage(imagePath)
+				h.AssertNil(t, err)
+			})
+
+			it.After(func() {
+				// We don't want to delete testdata/my-previous-image
+				imagePath = ""
+			})
+
+			it("returns true", func() {
+				h.AssertTrue(t, func() bool {
+					return image.Found()
+				})
+			})
+		})
+	})
+
 	when("#Delete", func() {
 		var image *layout.Image
 

local/local.go

@@ -72,6 +72,10 @@ func (i *Image) Found() bool {
 	return i.inspect.ID != ""
 }
 
+func (i *Image) Valid() bool {
+	return i.Found()
+}
+
 func (i *Image) GetAnnotateRefName() (string, error) {
 	return "", nil
 }

remote/remote.go

@@ -15,6 +15,7 @@ import (
 	"github.com/google/go-containerregistry/pkg/v1/remote/transport"
 	"github.com/google/go-containerregistry/pkg/v1/tarball"
 	"github.com/google/go-containerregistry/pkg/v1/types"
+	"github.com/google/go-containerregistry/pkg/v1/validate"
 	"github.com/pkg/errors"
 
 	"github.com/buildpacks/imgutil"
@@ -92,6 +93,7 @@ func (i *Image) Env(key string) (string, error) {
 
 func (i *Image) Found() bool {
 	_, err := i.found()
+
 	return err == nil
 }
 
@@ -104,6 +106,23 @@ func (i *Image) found() (*v1.Descriptor, error) {
 	return remote.Head(ref, remote.WithAuth(auth), remote.WithTransport(http.DefaultTransport))
 }
 
+func (i *Image) Valid() bool {
+	return i.valid() == nil
+}
+
+func (i *Image) valid() error {
+	reg := getRegistry(i.repoName, i.registrySettings)
+	ref, auth, err := referenceForRepoName(i.keychain, i.repoName, reg.insecure)
+	if err != nil {
+		return err
+	}
+	img, err := remote.Image(ref, remote.WithAuth(auth), remote.WithTransport(http.DefaultTransport))
+	if err != nil {
+		return err
+	}
+	return validate.Image(img, validate.Fast)
+}
+
 func (i *Image) GetAnnotateRefName() (string, error) {
 	// TODO issue https://github.com/buildpacks/imgutil/issues/178
 	return "", errors.New("not yet implemented")

remote/remote_test.go

@@ -1595,6 +1595,53 @@ func testImage(t *testing.T, when spec.G, it spec.S) {
 		})
 	})
 
+	when("#Valid", func() {
+		when("it exists", func() {
+			it("returns true", func() {
+				origImage, err := remote.NewImage(repoName, authn.DefaultKeychain)
+				h.AssertNil(t, err)
+				h.AssertNil(t, origImage.Save())
+
+				image, err := remote.NewImage(repoName, authn.DefaultKeychain)
+				h.AssertNil(t, err)
+
+				h.AssertEq(t, image.Valid(), true)
+			})
+		})
+
+		when("it is corrupt", func() {
+			it("returns false", func() {
+				origImage, err := remote.NewImage(repoName, authn.DefaultKeychain)
+				h.AssertNil(t, err)
+				tarPath, _, _ := h.RandomLayer(t, t.TempDir())
+				defer os.Remove(tarPath)
+				h.AssertNil(t, origImage.AddLayer(tarPath))
+				h.AssertNil(t, origImage.Save())
+
+				// delete the top layer from the registry
+				layers, err := origImage.UnderlyingImage().Layers()
+				h.AssertNil(t, err)
+				digest, err := layers[0].Digest()
+				h.AssertNil(t, err)
+				h.DeleteRegistryBlob(t, repoName, digest, dockerRegistry.EncodedAuth())
+
+				image, err := remote.NewImage(repoName, authn.DefaultKeychain)
+				h.AssertNil(t, err)
+
+				h.AssertEq(t, image.Valid(), false)
+			})
+		})
+
+		when("it does not exist", func() {
+			it("returns false", func() {
+				image, err := remote.NewImage(repoName, authn.DefaultKeychain)
+				h.AssertNil(t, err)
+
+				h.AssertEq(t, image.Valid(), false)
+			})
+		})
+	})
+
 	when("#Delete", func() {
 		when("it exists", func() {
 			var img imgutil.Image

testhelpers/docker_registry.go

@@ -174,7 +174,7 @@ func (r *DockerRegistry) Start(t *testing.T) {
 
 	if r.username != "" {
 		// Write Docker config and configure auth headers
-		writeDockerConfig(t, r.DockerDirectory, r.Host, r.Port, r.encodedAuth())
+		writeDockerConfig(t, r.DockerDirectory, r.Host, r.Port, r.EncodedAuth())
 	}
 }
 
@@ -294,7 +294,7 @@ func DockerHostname(t *testing.T) string {
 	return "localhost"
 }
 
-func (r *DockerRegistry) encodedAuth() string {
+func (r *DockerRegistry) EncodedAuth() string {
 	return base64.StdEncoding.EncodeToString([]byte(fmt.Sprintf("%s:%s", r.username, r.password)))
 }
 

testhelpers/testhelpers.go

@@ -13,6 +13,7 @@ import (
 	"io/ioutil"
 	"math/rand"
 	"net/http"
+	"net/url"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -227,6 +228,28 @@ func PushImage(t *testing.T, dockerCli dockercli.CommonAPIClient, refStr string)
 	AssertNil(t, err)
 }
 
+// DeleteRegistryBlob deletes the blob with the given digest from the registry by issuing an HTTP DELETE request.
+func DeleteRegistryBlob(t *testing.T, repoName string, digest v1.Hash, encodedAuth string) {
+	ref, err := name.ParseReference(repoName, name.WeakValidation)
+	AssertNil(t, err)
+	url := url.URL{
+		Scheme: ref.Context().Registry.Scheme(),
+		Host:   ref.Context().RegistryStr(),
+		Path:   fmt.Sprintf("/v2/%s/blobs/%s", ref.Context().RepositoryStr(), digest),
+	}
+	req, err := http.NewRequest(http.MethodDelete, url.String(), nil)
+	AssertNil(t, err)
+	req.Header.Add("Authorization", "Basic "+encodedAuth)
+	client := &http.Client{}
+	resp, err := client.Do(req)
+	AssertNil(t, err)
+	defer resp.Body.Close()
+
+	_, err = io.ReadAll(resp.Body)
+	AssertNil(t, err)
+	AssertEq(t, resp.StatusCode, http.StatusAccepted)
+}
+
 func ImageID(t *testing.T, repoName string) string {
 	t.Helper()
 	inspect, _, err := DockerCli(t).ImageInspectWithRaw(context.Background(), repoName)