datastore: fix handling of embedded unexported structs (#58)

datastore/prop.go

@@ -199,8 +199,8 @@ func getStructCodecLocked(t reflect.Type) (ret *structCodec, retErr error) {
 		f := t.Field(i)
 		// Skip unexported fields.
 		// Note that if f is an anonymous, unexported struct field,
-		// we will not promote its fields. We will skip f entirely.
-		if f.PkgPath != "" {
+		// we will promote its fields.
+		if f.PkgPath != "" && !f.Anonymous {
 			continue
 		}
 
@@ -253,11 +253,13 @@ func getStructCodecLocked(t reflect.Type) (ret *structCodec, retErr error) {
 					"datastore: flattening nested structs leads to a slice of slices: field %q", f.Name)
 			}
 			c.hasSlice = c.hasSlice || sub.hasSlice
-			// If name is empty at this point, f is an anonymous struct field.
-			// In this case, we promote the substruct's fields up to this level
+			// If f is an anonymous struct field, we promote the substruct's fields up to this level
 			// in the linked list of struct codecs.
-			if name == "" {
+			if f.Anonymous {
 				for subname, subfield := range sub.fields {
+					if name != "" {
+						subname = name + "." + subname
+					}
 					if _, ok := c.fields[subname]; ok {
 						return nil, fmt.Errorf("datastore: struct tag has repeated property name: %q", subname)
 					}

datastore/prop_test.go

@@ -97,6 +97,7 @@ func TestStructCodec(t *testing.T) {
 			"R": {path: []int{0}},
 			"S": {path: []int{1}, structCodec: pStructCodec},
 			"T": {path: []int{2}, structCodec: oStructCodec},
+			"O": {path: []int{3, 0}},
 		},
 		complete: true,
 	}
@@ -209,6 +210,7 @@ func TestStructCodec(t *testing.T) {
 					"B":   {path: []int{1}},
 					"CC":  {path: []int{2}, structCodec: oStructCodec},
 					"DDD": {path: []int{3}, structCodec: rStructCodec},
+					"O":   {path: []int{4, 0}},
 				},
 				complete: true,
 			},
@@ -224,9 +226,10 @@ func TestStructCodec(t *testing.T) {
 			}{},
 			&structCodec{
 				fields: map[string]fieldCodec{
-					"w":  {path: []int{1}},
-					"xx": {path: []int{2}, structCodec: oStructCodec},
-					"y":  {path: []int{3}, structCodec: rStructCodec},
+					"w":   {path: []int{1}},
+					"xx":  {path: []int{2}, structCodec: oStructCodec},
+					"y":   {path: []int{3}, structCodec: rStructCodec},
+					"z.O": {path: []int{4, 0}},
 				},
 				complete: true,
 			},
@@ -244,6 +247,7 @@ func TestStructCodec(t *testing.T) {
 				fields: map[string]fieldCodec{
 					"B": {path: []int{1}},
 					"D": {path: []int{3}, structCodec: uStructCodec},
+					"U": {path: []int{4, 0}},
 				},
 				complete: true,
 			},