check for noattestationsfound err

Signed-off-by: Meredith Lancaster <malancas@github.com>

pkg/cmd/attestation/download/download.go

@@ -2,6 +2,7 @@ package download
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"os"
 
@@ -128,14 +129,13 @@ func runDownload(opts *Options) error {
 	}
 	attestations, err := verification.GetRemoteAttestations(c)
 	if err != nil {
+		if errors.Is(err, api.ErrNoAttestations{}) {
+			fmt.Fprintf(opts.Logger.IO.Out, "No attestations found for %s\n", opts.ArtifactPath)
+			return nil
+		}
 		return fmt.Errorf("failed to fetch attestations: %w", err)
 	}
 
-	if attestations == nil {
-		fmt.Fprintf(opts.Logger.IO.Out, "No attestations found for %s\n", opts.ArtifactPath)
-		return nil
-	}
-
 	filePath := createJSONLinesFilePath(artifact.DigestWithAlg(), opts.OutputPath)
 	fmt.Fprintf(opts.Logger.IO.Out, "Writing attestations to file %s.\nAny previous content will be overwritten\n\n", filePath)
 

pkg/cmd/attestation/download/download_test.go

@@ -252,7 +252,7 @@ func TestRunDownload(t *testing.T) {
 		opts := baseOpts
 		opts.APIClient = api.MockClient{
 			OnGetByOwnerAndDigest: func(repo, digest string, limit int) ([]*api.Attestation, error) {
-				return nil, nil
+				return nil, api.ErrNoAttestations{}
 			},
 		}
 
@@ -264,6 +264,18 @@ func TestRunDownload(t *testing.T) {
 		require.NoFileExists(t, artifact.DigestWithAlg())
 	})
 
+	t.Run("failed to fetch attestations", func(t *testing.T) {
+		opts := baseOpts
+		opts.APIClient = api.MockClient{
+			OnGetByOwnerAndDigest: func(repo, digest string, limit int) ([]*api.Attestation, error) {
+				return nil, fmt.Errorf("failed to fetch attestations")
+			},
+		}
+
+		err := runDownload(&opts)
+		require.Error(t, err)
+	})
+
 	t.Run("cannot download OCI artifact", func(t *testing.T) {
 		opts := baseOpts
 		opts.ArtifactPath = "oci://ghcr.io/github/test"