Implement digest field in ociImageRef lens

Author: Marko Mikulicic

man/knot8.1

@@ -436,11 +436,11 @@ Sometimes there is no lens that works with your actual field format.
 When the relevant parts of the field format can be expressed with a regular expression you can
 use the "regexp" lens, where the format is expressed in-line in the field definition itself.
 .Pp
-For example, the ociImageRef lens currently doesn't support the digest field; as an alternative we can use
-the regexp lens to select the digest body.
+For example, you can locate a docker image name inside of some configuration file (e.g. a jsonnet file)
+and then use the ociImageRef lens to further parse the image reference.
 .
 .Bd -literal -offset indent
-  field.knot8.io/workerImageDigest: /spec/template/spec/containers/~{"name":"runner"}/image/~(regexp)/@sha256:([a-f0-9]*)/1
+  field.knot8.io/workerImageDigest: "/data/worker-ubuntu16-04.jsonnet/~(regexp)/{ name: 'container-image', value: 'docker:~1~1([^']*)/1/~(ociImageRef)/digest"
 .Ed
 .
 . When the ociImageRef finally implements the digest field we can rewrite this field definition while maintaining backward compatibility.

pkg/lensed/oci.go

@@ -31,7 +31,7 @@ func (OCIImageRef) Apply(src []byte, vals []Setter) ([]byte, error) {
 			return nil, fmt.Errorf("unexpected path len. got: %d, max: %d", l, m)
 		}
 
-		r, err := regexp.Compile("^([^:]*)(:(.*))?$")
+		r, err := regexp.Compile("^([^:@]*)(:([^@]*))?(@sha256:([a-f0-9]*))?$")
 		if err != nil {
 			return nil, err
 		}
@@ -43,10 +43,11 @@ func (OCIImageRef) Apply(src []byte, vals []Setter) ([]byte, error) {
 			comp = 1
 		case "tag":
 			comp = 3
+		case "digest":
+			comp = 5
 		default:
 			return nil, fmt.Errorf("unknown ociImageRef field %q", p)
 		}
-
 		start, end := indices[2*comp+0], indices[2*comp+1]
 
 		var oldval []byte
@@ -62,7 +63,16 @@ func (OCIImageRef) Apply(src []byte, vals []Setter) ([]byte, error) {
 
 		if start == -1 {
 			start, end = indices[1], indices[1]
-			newval = append([]byte(":"), newval...)
+			var sep string
+			switch p := path[0]; p {
+			case "tag":
+				sep = ":"
+			case "digest":
+				sep = "@sha256:"
+			default:
+				return nil, fmt.Errorf("unknown ociImageRef field %q", p)
+			}
+			newval = append([]byte(sep), newval...)
 		}
 
 		ops = append(ops, splice.Span(start, end).With(string(newval)))

pkg/lensed/oci_test.go

@@ -35,6 +35,27 @@ func TestOCIImageRef(t *testing.T) {
 			},
 			"image: foo/bar:baz",
 		},
+		{
+			"image: foo/bar@sha256:cbbf2f9a99b47fc460d422812b6a5adff7dfee951d8fa2e4a98caa0382cfbdbf",
+			[]Mapping{
+				{"/image/~(ociImageRef)/digest", "7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc"},
+			},
+			"image: foo/bar@sha256:7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc",
+		},
+		{
+			"image: foo/bar:1.0@sha256:cbbf2f9a99b47fc460d422812b6a5adff7dfee951d8fa2e4a98caa0382cfbdbf",
+			[]Mapping{
+				{"/image/~(ociImageRef)/digest", "7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc"},
+			},
+			"image: foo/bar:1.0@sha256:7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc",
+		},
+		{
+			"image: foo/bar",
+			[]Mapping{
+				{"/image/~(ociImageRef)/digest", "7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc"},
+			},
+			"image: foo/bar@sha256:7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc",
+		},
 	}
 
 	for i, tc := range testCases {

pkg/lensed/regexp_test.go

@@ -46,6 +46,13 @@ func TestRegexp(t *testing.T) {
 			},
 			out,
 		},
+		{
+			"foo:YmFy",
+			[]Mapping{
+				{"~(regexp)/foo:(.*)/1/~(base64)", "baz"},
+			},
+			"foo:YmF6",
+		},
 	}
 
 	for i, tc := range testCases {