Merge pull request #1428 from tonistiigi/imagemeta-async

llb: update image meta resolver to async callback

client/llb/resolver.go

@@ -14,6 +14,15 @@ func WithMetaResolver(mr ImageMetaResolver) ImageOption {
 	})
 }
 
+// ResolveDigest uses the meta resolver to update the ref of image with full digest before marshaling.
+// This makes image ref immutable and is recommended if you want to make sure meta resolver data
+// matches the image used during the build.
+func ResolveDigest(v bool) ImageOption {
+	return imageOptionFunc(func(ii *ImageInfo) {
+		ii.resolveDigest = v
+	})
+}
+
 // ImageMetaResolver can resolve image config metadata from a reference
 type ImageMetaResolver interface {
 	ResolveImageConfig(ctx context.Context, ref string, opt ResolveImageConfigOpt) (digest.Digest, []byte, error)

client/llb/resolver_test.go

@@ -0,0 +1,91 @@
+package llb
+
+import (
+	"context"
+	"encoding/json"
+	"testing"
+
+	"github.com/moby/buildkit/solver/pb"
+	digest "github.com/opencontainers/go-digest"
+	"github.com/pkg/errors"
+	"github.com/stretchr/testify/require"
+)
+
+func TestImageMetaResolver(t *testing.T) {
+	t.Parallel()
+	tr := &testResolver{
+		digest: digest.FromBytes([]byte("foo")),
+		dir:    "/bar",
+	}
+	st := Image("alpine", WithMetaResolver(tr))
+
+	require.Equal(t, false, tr.called)
+
+	def, err := st.Marshal(context.TODO())
+	require.NoError(t, err)
+
+	require.Equal(t, true, tr.called)
+
+	m, arr := parseDef(t, def.Def)
+	require.Equal(t, 2, len(arr))
+
+	dgst, idx := last(t, arr)
+	require.Equal(t, 0, idx)
+	require.Equal(t, m[dgst], arr[0])
+
+	require.Equal(t, "docker-image://docker.io/library/alpine:latest", arr[0].Op.(*pb.Op_Source).Source.GetIdentifier())
+
+	d, err := st.GetDir(context.TODO())
+	require.NoError(t, err)
+	require.Equal(t, "/bar", d)
+}
+
+func TestImageResolveDigest(t *testing.T) {
+	t.Parallel()
+
+	st := Image("alpine", WithMetaResolver(&testResolver{
+		digest: digest.FromBytes([]byte("bar")),
+		dir:    "/foo",
+	}), ResolveDigest(true))
+
+	def, err := st.Marshal(context.TODO())
+	require.NoError(t, err)
+
+	m, arr := parseDef(t, def.Def)
+	require.Equal(t, 2, len(arr))
+
+	dgst, idx := last(t, arr)
+	require.Equal(t, 0, idx)
+	require.Equal(t, m[dgst], arr[0])
+
+	require.Equal(t, "docker-image://docker.io/library/alpine:latest@"+string(digest.FromBytes([]byte("bar"))), arr[0].Op.(*pb.Op_Source).Source.GetIdentifier())
+
+	d, err := st.GetDir(context.TODO())
+	require.NoError(t, err)
+	require.Equal(t, "/foo", d)
+}
+
+type testResolver struct {
+	digest digest.Digest
+	dir    string
+	called bool
+}
+
+func (r *testResolver) ResolveImageConfig(ctx context.Context, ref string, opt ResolveImageConfigOpt) (digest.Digest, []byte, error) {
+	var img struct {
+		Config struct {
+			Env        []string `json:"Env,omitempty"`
+			WorkingDir string   `json:"WorkingDir,omitempty"`
+			User       string   `json:"User,omitempty"`
+		} `json:"config,omitempty"`
+	}
+	r.called = true
+
+	img.Config.WorkingDir = r.dir
+
+	dt, err := json.Marshal(img)
+	if err != nil {
+		return "", nil, errors.WithStack(err)
+	}
+	return r.digest, dt, nil
+}

client/llb/source.go

@@ -92,7 +92,8 @@ func (s *SourceOp) Inputs() []Output {
 func Image(ref string, opts ...ImageOption) State {
 	r, err := reference.ParseNormalizedNamed(ref)
 	if err == nil {
-		ref = reference.TagNameOnly(r).String()
+		r = reference.TagNameOnly(r)
+		ref = r.String()
 	}
 	var info ImageInfo
 	for _, opt := range opts {
@@ -116,21 +117,35 @@ func Image(ref string, opts ...ImageOption) State {
 	src := NewSource("docker-image://"+ref, attrs, info.Constraints) // controversial
 	if err != nil {
 		src.err = err
-	}
-	if info.metaResolver != nil {
-		_, dt, err := info.metaResolver.ResolveImageConfig(context.TODO(), ref, ResolveImageConfigOpt{
+	} else if info.metaResolver != nil {
+		if _, ok := r.(reference.Digested); ok || !info.resolveDigest {
+			return NewState(src.Output()).Async(func(ctx context.Context, st State) (State, error) {
+				_, dt, err := info.metaResolver.ResolveImageConfig(ctx, ref, ResolveImageConfigOpt{
 					Platform:    info.Constraints.Platform,
 					ResolveMode: info.resolveMode.String(),
 				})
 				if err != nil {
-			src.err = err
-		} else {
-			st, err := NewState(src.Output()).WithImageConfig(dt)
-			if err == nil {
-				return st
+					return State{}, err
 				}
-			src.err = err
+				return st.WithImageConfig(dt)
+			})
 		}
+		return Scratch().Async(func(ctx context.Context, _ State) (State, error) {
+			dgst, dt, err := info.metaResolver.ResolveImageConfig(context.TODO(), ref, ResolveImageConfigOpt{
+				Platform:    info.Constraints.Platform,
+				ResolveMode: info.resolveMode.String(),
+			})
+			if err != nil {
+				return State{}, err
+			}
+			if dgst != "" {
+				r, err = reference.WithDigest(r, dgst)
+				if err != nil {
+					return State{}, err
+				}
+			}
+			return NewState(NewSource("docker-image://"+r.String(), attrs, info.Constraints).Output()).WithImageConfig(dt)
+		})
 	}
 	return NewState(src.Output())
 }
@@ -177,6 +192,7 @@ func (r ResolveMode) String() string {
 type ImageInfo struct {
 	constraintsWrapper
 	metaResolver  ImageMetaResolver
+	resolveDigest bool
 	resolveMode   ResolveMode
 	RecordType    string
 }