Fix bug in ReadDigest() function

pkg/dirimage/read.go

@@ -137,5 +137,6 @@ func ReadDigest(dir string) (v1.Hash, error) {
 		return v1.Hash{}, fmt.Errorf("failed to marshal manifest to JSON: %w", err)
 	}
 	hash := sha256.Sum256(jsonData)
-	return v1.NewHash(string(hash[:]))
+	hashString := fmt.Sprintf("sha256:%x", hash)
+	return v1.NewHash(hashString[:])
 }

pkg/dirimage/read_test.go

@@ -0,0 +1,99 @@
+package dirimage
+
+import (
+	"crypto/sha256"
+	"encoding/json"
+	"fmt"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// Helper function to write a manifest to a directory
+func writeManifest(t *testing.T, dir string, manifest *v1.Manifest) {
+	t.Helper()
+	data, err := json.Marshal(manifest)
+	assert.NoError(t, err)
+
+	err = os.WriteFile(filepath.Join(dir, LocalManifestFilename), data, 0644)
+	assert.NoError(t, err)
+}
+
+func mustHash(t *testing.T, s string) v1.Hash {
+	h, err := v1.NewHash(s)
+	require.NoError(t, err)
+	return h
+}
+
+func TestReadDigest_Success(t *testing.T) {
+	// Create a temporary directory for the test
+	dir, err := os.MkdirTemp("", "test-manifest")
+	assert.NoError(t, err)
+	defer os.RemoveAll(dir)
+
+	// Create a sample v1.Manifest object
+	manifest := &v1.Manifest{
+		SchemaVersion: 2,
+		MediaType:     "application/vnd.docker.distribution.manifest.v2+json",
+		Config: v1.Descriptor{
+			MediaType: "application/vnd.docker.container.image.v1+json",
+			Size:      1234,
+			Digest:    mustHash(t, "sha256:1234567812345678123456781234567812345678123456781234567812345678"),
+		},
+		Layers: []v1.Descriptor{
+			{
+				MediaType: "application/vnd.docker.image.rootfs.diff.tar.gzip",
+				Size:      5678,
+				Digest:    mustHash(t, "sha256:1234567812345678123456781234567812345678123456781234567812345678"),
+			},
+		},
+	}
+
+	// Write the manifest to the directory
+	writeManifest(t, dir, manifest)
+
+	// Read the digest
+	digest, err := ReadDigest(dir)
+	assert.NoError(t, err)
+
+	// Manually calculate the expected hash
+	jsonData, err := json.Marshal(manifest)
+	assert.NoError(t, err)
+	expectedHash := sha256.Sum256(jsonData)
+	expectedDigest, err := v1.NewHash(fmt.Sprintf("sha256:%x", expectedHash[:]))
+	assert.NoError(t, err)
+
+	// Compare the calculated digest with the expected digest
+	assert.Equal(t, expectedDigest, digest)
+}
+
+func TestReadDigest_ManifestNotFound(t *testing.T) {
+	// Create a temporary directory for the test
+	dir, err := os.MkdirTemp("", "test-manifest-not-found")
+	assert.NoError(t, err)
+	defer os.RemoveAll(dir)
+
+	// Try reading the digest from a directory without a manifest
+	_, err = ReadDigest(dir)
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "unable to read manifest")
+}
+
+func TestReadDigest_InvalidManifest(t *testing.T) {
+	// Create a temporary directory for the test
+	dir, err := os.MkdirTemp("", "test-invalid-manifest")
+	assert.NoError(t, err)
+	defer os.RemoveAll(dir)
+
+	// Write invalid manifest data
+	err = os.WriteFile(filepath.Join(dir, LocalManifestFilename), []byte("invalid json"), 0644)
+	assert.NoError(t, err)
+
+	// Try reading the digest
+	_, err = ReadDigest(dir)
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "invalid character 'i' looking for beginning of value")
+}