build: Fix iidfile for containerd-backed Docker driver

build/opt.go

@@ -491,6 +491,10 @@ func toSolveOpt(ctx context.Context, np *noderesolver.ResolvedNode, multiDriver
 		}
 		if e.Type == "image" && nodeDriver.IsMobyDriver() {
 			opt.Exports[i].Type = "moby"
+			// The containerd image store resolves images by manifest or index digest.
+			if nodeDriver.Features(ctx)[driver.PreferImageDigest] {
+				opt.Exports[i].Attrs["prefer-image-digest"] = "true"
+			}
 			if e.Attrs["push"] != "" {
 				if ok, _ := strconv.ParseBool(e.Attrs["push"]); ok {
 					if ok, _ := strconv.ParseBool(e.Attrs["push-by-digest"]); ok {

commands/build.go

@@ -463,7 +463,7 @@ func runBuild(ctx context.Context, dockerCli command.Cli, debugOpts debuggerOpti
 	return nil
 }
 
-// getImageID returns the image ID - the digest of the image config
+// getImageID returns the image identifier selected for the export destination.
 func getImageID(resp map[string]string) string {
 	dgst := resp[exptypes.ExporterImageDigestKey]
 	if v, ok := resp[exptypes.ExporterImageConfigDigestKey]; ok {

driver/docker/driver.go

@@ -92,12 +92,13 @@ func (d *Driver) Features(ctx context.Context) map[driver.Feature]bool {
 			c.Close()
 		}
 		d.features.list = map[driver.Feature]bool{
-			driver.OCIExporter:    useContainerdSnapshotter,
-			driver.DockerExporter: useContainerdSnapshotter,
-			driver.CacheExport:    useContainerdSnapshotter,
-			driver.MultiPlatform:  useContainerdSnapshotter,
-			driver.DirectPush:     useContainerdSnapshotter,
-			driver.DefaultLoad:    true,
+			driver.OCIExporter:       useContainerdSnapshotter,
+			driver.DockerExporter:    useContainerdSnapshotter,
+			driver.CacheExport:       useContainerdSnapshotter,
+			driver.MultiPlatform:     useContainerdSnapshotter,
+			driver.DirectPush:        useContainerdSnapshotter,
+			driver.PreferImageDigest: useContainerdSnapshotter,
+			driver.DefaultLoad:       true,
 		}
 	})
 	return d.features.list

driver/features.go

@@ -8,5 +8,6 @@ const DockerExporter Feature = "Docker exporter"
 const CacheExport Feature = "Cache export"
 const MultiPlatform Feature = "Multi-platform build"
 const DirectPush Feature = "Direct push"
+const PreferImageDigest Feature = "Prefer image digest"
 
 const DefaultLoad Feature = "Automatically load images to the Docker Engine image store"

tests/build.go

@@ -682,12 +682,19 @@ func testImageIDOutput(t *testing.T, sb integration.Sandbox) {
 	err = json.Unmarshal(dt, &md)
 	require.NoError(t, err)
 
-	require.NotEmpty(t, md.ConfigDigest)
 	require.NotEmpty(t, md.Digest)
+	if !isMobyContainerdSnapWorker(sb) {
+		require.NotEmpty(t, md.ConfigDigest)
+	}
 
 	// verify the image ID output is correct
-	// XXX: improve this by checking that it's one of the two expected digests depending on the scenario.
 	require.Contains(t, []digest.Digest{digest.Digest(md.ConfigDigest), digest.Digest(md.Digest)}, dgst)
+
+	if sb.DockerAddress() != "" {
+		cmd = dockerCmd(sb, withArgs("image", "inspect", imageID))
+		out, err := cmd.CombinedOutput()
+		require.NoError(t, err, string(out))
+	}
 }
 
 func testBuildMobyFromLocalImage(t *testing.T, sb integration.Sandbox) {