internal/core/convert: fix for embedded structs are not honored

Fixes #376.

I added [a comment](cuelang/cue#376 (comment)) to #376 with some questions. Would be great if I could get some feedback on that as well as my proposed fix. My experience with cue is very limited.

Closes #568
cuelang/cue#568

GitOrigin-RevId: 00851951dfd10dd11489c99f1507d2f2c880183c
Change-Id: Ia857cdb14739e232a6028ebc32ee1a6a11494ebf
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/7684
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>

encoding/gocode/gocodec/codec_test.go

@@ -266,6 +266,38 @@ func TestDecode(t *testing.T) {
 	}{{
 		in:   "str",
 		want: `"str"`,
+	}, {
+		in: func() interface{} {
+			type T struct {
+				B int
+			}
+			type S struct {
+				A string
+				T
+			}
+			return S{}
+		}(),
+		want: `{
+	A: ""
+	B: 0
+}`,
+	}, {
+		in: func() interface{} {
+			type T struct {
+				B int
+			}
+			type S struct {
+				A string
+				T `json:"t"`
+			}
+			return S{}
+		}(),
+		want: `{
+	A: ""
+	t: {
+		B: 0
+	}
+}`,
 	}}
 	c := New(&cue.Runtime{}, nil)
 

internal/core/convert/go.go

@@ -99,6 +99,9 @@ var tagsWithNames = []string{"json", "yaml", "protobuf"}
 
 func getName(f *reflect.StructField) string {
 	name := f.Name
+	if f.Anonymous {
+		name = ""
+	}
 	for _, s := range tagsWithNames {
 		if tag, ok := f.Tag.Lookup(s); ok {
 			if p := strings.Index(tag, ","); p >= 0 {
@@ -405,18 +408,18 @@ func convertRec(ctx *adt.OpContext, nilIsTop bool, x interface{}) adt.Value {
 
 			t := value.Type()
 			for i := 0; i < value.NumField(); i++ {
-				t := t.Field(i)
-				if t.PkgPath != "" {
+				sf := t.Field(i)
+				if sf.PkgPath != "" {
 					continue
 				}
 				val := value.Field(i)
 				if !nilIsTop && isNil(val) {
 					continue
 				}
-				if tag, _ := t.Tag.Lookup("json"); tag == "-" {
+				if tag, _ := sf.Tag.Lookup("json"); tag == "-" {
 					continue
 				}
-				if isOmitEmpty(&t) && isZero(val) {
+				if isOmitEmpty(&sf) && isZero(val) {
 					continue
 				}
 				sub := convertRec(ctx, nilIsTop, val.Interface())
@@ -430,10 +433,21 @@ func convertRec(ctx *adt.OpContext, nilIsTop bool, x interface{}) adt.Value {
 
 				// leave errors like we do during normal evaluation or do we
 				// want to return the error?
-				name := getName(&t)
+				name := getName(&sf)
 				if name == "-" {
 					continue
 				}
+				if sf.Anonymous && name == "" {
+					arc, ok := sub.(*adt.Vertex)
+					if ok {
+						for _, a := range arc.Arcs {
+							obj.Decls = append(obj.Decls, &adt.Field{Label: a.Label, Value: a.Value})
+							v.Arcs = append(v.Arcs, a)
+						}
+					}
+					continue
+				}
+
 				f := ctx.StringLabel(name)
 				obj.Decls = append(obj.Decls, &adt.Field{Label: f, Value: sub})
 				arc, ok := sub.(*adt.Vertex)

internal/core/convert/go_test.go

@@ -183,6 +183,21 @@ func TestConvert(t *testing.T) {
 		reflect.ValueOf(3), "3",
 	}, {
 		time.Date(2019, 4, 1, 0, 0, 0, 0, time.UTC), `(string){ "2019-04-01T00:00:00Z" }`,
+	}, {
+		func() interface{} {
+			type T struct {
+				B int
+			}
+			type S struct {
+				A string
+				T
+			}
+			return S{}
+		}(),
+		`(struct){
+  A: (string){ "" }
+  B: (int){ 0 }
+}`,
 	}}
 	r := runtime.New()
 	for _, tc := range testCases {