catalogd never uses filesystem cache for image references with tags

[m1kola]

Steps to reproduce

1. Create a ClusterCatalog which uses an image ref with a tag

   apiVersion: olm.operatorframework.io/v1alpha1
   kind: ClusterCatalog
   metadata:
     name: operatorhubio
   spec:
     source:
       type: image
       image:
         ref: quay.io/operatorhubio/catalog:latest
         pollInterval: 5s

2. Observe logs

Expected result

On a second poll (after 5 seconds in our example) you should see a log line (code) saying that we hit the cache containing the following string:

found image in filesystem cache

Actual results

No log line/cache hit.

Analysis

We never enter this condition because isDigest is always false:

catalogd/internal/source/image_registry_client.go

Lines 80 to 88 in 4323184

	digest, isDigest := imgRef.(name.Digest)
	if isDigest {
	hexVal := strings.TrimPrefix(digest.DigestStr(), "sha256:")
	unpackPath := filepath.Join(i.BaseCachePath, catalog.Name, hexVal)
	if stat, err := os.Stat(unpackPath); err == nil && stat.IsDir() {
	l.V(1).Info("found image in filesystem cache", "digest", hexVal)
	return unpackedResult(os.DirFS(unpackPath), catalog, digest.String(), metav1.Time{Time: time.Now()}), nil
	}
	}

This is because imgRef is just a parsed .spec.source.image.ref. We only resolve the ref below: after checking the cache. So if this field contains a ref with a tag - we only write into the filesystem cache and never read from it.

We have test cases for both digest and tag image refs, but the test is somehow green. The test is very complex and has a lot of parameters so I suspect there is a bug within the test somewhere.

[m1kola]

It looks like "tag based image, digest already exists in cache" test case supposed to hit cache, but doesn't.