Address review: memoize per-service, expand image-mount tests, clarify doc comment

Author: ssam18

types/project.go

@@ -575,12 +575,29 @@ func (p *Project) WithServicesDisabled(names ...string) *Project {
 	return newProject
 }
 
-// WithImagesResolved updates services images to include digest computed by a resolver function
-// It returns a new Project instance with the changes and keep the original Project unchanged
+// WithImagesResolved updates services to pin both service.Image and image-mount
+// volume sources (type=image) to digests computed by the resolver. It returns a
+// new Project with the changes and keeps the original Project unchanged. Within
+// each service, repeated lookups for the same image reference are deduplicated
+// so callers that hit a registry per resolve aren't charged twice when the
+// service image and an image-mount volume reference the same tag.
 func (p *Project) WithImagesResolved(resolver func(named reference.Named) (godigest.Digest, error)) (*Project, error) {
 	return p.WithServicesTransform(func(_ string, service ServiceConfig) (ServiceConfig, error) {
+		cache := map[string]string{}
+		resolve := func(img string) (string, error) {
+			if r, ok := cache[img]; ok {
+				return r, nil
+			}
+			r, err := resolveImageDigest(img, resolver)
+			if err != nil {
+				return img, err
+			}
+			cache[img] = r
+			return r, nil
+		}
+
 		if service.Image != "" {
-			resolved, err := resolveImageDigest(service.Image, resolver)
+			resolved, err := resolve(service.Image)
 			if err != nil {
 				return service, err
 			}
@@ -591,7 +608,7 @@ func (p *Project) WithImagesResolved(resolver func(named reference.Named) (godig
 			if volume.Type != VolumeTypeImage || volume.Source == "" {
 				continue
 			}
-			resolved, err := resolveImageDigest(volume.Source, resolver)
+			resolved, err := resolve(volume.Source)
 			if err != nil {
 				return service, err
 			}

types/project_test.go

@@ -247,6 +247,95 @@ func Test_ResolveImages_imageMount(t *testing.T) {
 	assert.Equal(t, app.Volumes[1].Source, "/host/path")
 }
 
+func Test_ResolveImages_imageMount_noServiceImage(t *testing.T) {
+	const dgst = "sha256:1234567890123456789012345678901234567890123456789012345678901234"
+	resolver := func(_ reference.Named) (digest.Digest, error) {
+		return dgst, nil
+	}
+	p := &Project{
+		Services: Services{
+			"app": ServiceConfig{
+				Name: "app",
+				// no service.Image — the service is defined purely by its image-mount volume.
+				Volumes: []ServiceVolumeConfig{
+					{
+						Type:   VolumeTypeImage,
+						Source: "busybox:latest",
+						Target: "/test_mount",
+					},
+				},
+			},
+		},
+	}
+
+	p, err := p.WithImagesResolved(resolver)
+	assert.NilError(t, err)
+
+	app := p.Services["app"]
+	assert.Equal(t, app.Image, "")
+	assert.Equal(t, app.Volumes[0].Source, "docker.io/library/busybox:latest@"+dgst)
+}
+
+func Test_ResolveImages_imageMount_alreadyCanonical(t *testing.T) {
+	const dgst = "sha256:1234567890123456789012345678901234567890123456789012345678901234"
+	resolverCalls := 0
+	resolver := func(_ reference.Named) (digest.Digest, error) {
+		resolverCalls++
+		return dgst, nil
+	}
+	pinned := "docker.io/library/busybox@" + dgst
+	p := &Project{
+		Services: Services{
+			"app": ServiceConfig{
+				Name:  "app",
+				Image: pinned,
+				Volumes: []ServiceVolumeConfig{
+					{
+						Type:   VolumeTypeImage,
+						Source: pinned,
+						Target: "/test_mount",
+					},
+				},
+			},
+		},
+	}
+
+	p, err := p.WithImagesResolved(resolver)
+	assert.NilError(t, err)
+
+	app := p.Services["app"]
+	// already-canonical references are passed through unchanged.
+	assert.Equal(t, app.Image, pinned)
+	assert.Equal(t, app.Volumes[0].Source, pinned)
+	// and the resolver is never called for canonical references.
+	assert.Equal(t, resolverCalls, 0)
+}
+
+func Test_ResolveImages_imageMount_unresolvable(t *testing.T) {
+	resolver := func(_ reference.Named) (digest.Digest, error) {
+		return "", errors.New("manifest unknown")
+	}
+	p := &Project{
+		Services: Services{
+			"app": ServiceConfig{
+				Name: "app",
+				Volumes: []ServiceVolumeConfig{
+					{
+						Type:   VolumeTypeImage,
+						Source: "registry.example/missing:1.0",
+						Target: "/test_mount",
+					},
+				},
+			},
+		},
+	}
+
+	_, err := p.WithImagesResolved(resolver)
+	// failure to resolve an image-mount source must surface as an error,
+	// same as for service.Image.
+	assert.Error(t, err, "manifest unknown")
+}
+
 func Test_ResolveImages_concurrent(t *testing.T) {
 	const garfield = "sha256:1234567890123456789012345678901234567890123456789012345678901234"
 	resolver := func(_ reference.Named) (digest.Digest, error) {