proxy: Make OpenImageOptional work with oci-archive:

By adding the standard ENOENT to our list of errors.

I hit this while working on
coreos/rpm-ostree#4598
which is a tool that builds base images and wants to query
if the image exists beforehand.

Signed-off-by: Colin Walters <[email protected]>

cmd/skopeo/proxy.go

@@ -73,6 +73,7 @@ import (
 
 	"github.com/containers/image/v5/image"
 	"github.com/containers/image/v5/manifest"
+	ociarchive "github.com/containers/image/v5/oci/archive"
 	ocilayout "github.com/containers/image/v5/oci/layout"
 	"github.com/containers/image/v5/pkg/blobinfocache"
 	"github.com/containers/image/v5/transports"
@@ -229,13 +230,22 @@ func isDockerManifestUnknownError(err error) bool {
 	return ec.ErrorCode() == dockerdistributionapi.ErrorCodeManifestUnknown
 }
 
+func isOciImageNotFound(err error) bool {
+	var lerr ocilayout.ImageNotFoundError
+	if errors.As(err, &lerr) {
+		return true
+	}
+	var aerr ociarchive.ImageNotFoundError
+	return errors.As(err, &aerr)
+}
+
 // isNotFoundImageError heuristically attempts to determine whether an error
 // is saying the remote source couldn't find the image (as opposed to an
 // authentication error, an I/O error etc.)
 // TODO drive this into containers/image properly
 func isNotFoundImageError(err error) bool {
 	return isDockerManifestUnknownError(err) ||
-		errors.Is(err, ocilayout.ImageNotFoundError{})
+		isOciImageNotFound(err)
 }
 
 func (h *proxyHandler) openImageImpl(args []any, allowNotFound bool) (retReplyBuf replyBuf, retErr error) {

integration/proxy_test.go

@@ -332,6 +332,15 @@ func runTestOpenImageOptionalNotFound(p *proxy, img string) error {
 	return nil
 }
 
+// Verify that we do see an error if the parent directory doesn't exist
+func runTestOpenImageOptionalNoParentDirectory(p *proxy) error {
+	_, err := p.callNoFd("OpenImageOptional", []any{"oci-archive:/no/such/parent/directory/foo.ociarchive"})
+	if err == nil {
+		return fmt.Errorf("Successfully opened nonexistent parent directory")
+	}
+	return nil
+}
+
 func (s *proxySuite) TestProxy() {
 	t := s.T()
 	p, err := newProxy()
@@ -354,4 +363,14 @@ func (s *proxySuite) TestProxy() {
 		err = fmt.Errorf("Testing optional image %s: %v", knownNotExtantImage, err)
 	}
 	assert.NoError(t, err)
+
+	nonExistentArchive := "oci-archive:/enoent"
+	err = runTestOpenImageOptionalNotFound(p, nonExistentArchive)
+	if err != nil {
+		err = fmt.Errorf("Testing optional image %s: %v", nonExistentArchive, err)
+	}
+	assert.NoError(t, err)
+
+	err = runTestOpenImageOptionalNoParentDirectory(p)
+	assert.NoError(t, err)
 }