standardize behavior of mapping anonymous fields

the behavior has been defined in a way that is compatible with
encoding/json.  this behavior is as follows:

anonymous fields which are structs will have struct fields get
field names as if they were directly in the parent struct.

anonymous fields which are not structs, or which are interfaces
which may or may not point to structs will get field names that
correspond to the name of the type

the exception to the rules above is that you can always override
this behavior by using a JSON struct tag

fixes #101

Author: mschoch

mapping_document.go

@@ -325,20 +325,29 @@ func (dm *DocumentMapping) walkDocument(data interface{}, path []string, indexes
 		for i := 0; i < val.NumField(); i++ {
 			field := typ.Field(i)
 			fieldName := field.Name
+			// anonymous fields of type struct can elide the type name
+			if field.Anonymous && field.Type.Kind() == reflect.Struct {
+				fieldName = ""
+			}
 
 			// if the field has a JSON name, prefer that
 			jsonTag := field.Tag.Get("json")
 			jsonFieldName := parseJSONTagName(jsonTag)
 			if jsonFieldName == "-" {
 				continue
 			}
-			if jsonFieldName != "" {
+			// allow json tag to set field name to empty, only if anonymous
+			if field.Tag != "" && (jsonFieldName != "" || field.Anonymous) {
 				fieldName = jsonFieldName
 			}
 
 			if val.Field(i).CanInterface() {
 				fieldVal := val.Field(i).Interface()
-				dm.processProperty(fieldVal, append(path, fieldName), indexes, context)
+				newpath := path
+				if fieldName != "" {
+					newpath = append(path, fieldName)
+				}
+				dm.processProperty(fieldVal, newpath, indexes, context)
 			}
 		}
 	case reflect.Slice, reflect.Array:

mapping_test.go

@@ -603,3 +603,124 @@ func TestMappingBug353(t *testing.T) {
 		}
 	}
 }
+
+func TestAnonymousStructFields(t *testing.T) {
+
+	type Contact0 string
+
+	type Contact1 struct {
+		Name string
+	}
+
+	type Contact2 interface{}
+
+	type Contact3 interface{}
+
+	type Thing struct {
+		Contact0
+		Contact1
+		Contact2
+		Contact3
+	}
+
+	x := Thing{
+		Contact0: "hello",
+		Contact1: Contact1{
+			Name: "marty",
+		},
+		Contact2: Contact1{
+			Name: "will",
+		},
+		Contact3: "steve",
+	}
+
+	doc := document.NewDocument("1")
+	m := NewIndexMapping()
+	err := m.mapDocument(doc, x)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(doc.Fields) != 4 {
+		t.Fatalf("expected 4 fields, got %d", len(doc.Fields))
+	}
+	if doc.Fields[0].Name() != "Contact0" {
+		t.Errorf("expected field named 'Contact0', got '%s'", doc.Fields[0].Name())
+	}
+	if doc.Fields[1].Name() != "Name" {
+		t.Errorf("expected field named 'Name', got '%s'", doc.Fields[1].Name())
+	}
+	if doc.Fields[2].Name() != "Contact2.Name" {
+		t.Errorf("expected field named 'Contact2.Name', got '%s'", doc.Fields[2].Name())
+	}
+	if doc.Fields[3].Name() != "Contact3" {
+		t.Errorf("expected field named 'Contact3', got '%s'", doc.Fields[3].Name())
+	}
+
+	type AnotherThing struct {
+		Contact0 `json:"Alternate0"`
+		Contact1 `json:"Alternate1"`
+		Contact2 `json:"Alternate2"`
+		Contact3 `json:"Alternate3"`
+	}
+
+	y := AnotherThing{
+		Contact0: "hello",
+		Contact1: Contact1{
+			Name: "marty",
+		},
+		Contact2: Contact1{
+			Name: "will",
+		},
+		Contact3: "steve",
+	}
+
+	doc2 := document.NewDocument("2")
+	err = m.mapDocument(doc2, y)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(doc2.Fields) != 4 {
+		t.Fatalf("expected 4 fields, got %d", len(doc2.Fields))
+	}
+	if doc2.Fields[0].Name() != "Alternate0" {
+		t.Errorf("expected field named 'Alternate0', got '%s'", doc2.Fields[0].Name())
+	}
+	if doc2.Fields[1].Name() != "Alternate1.Name" {
+		t.Errorf("expected field named 'Name', got '%s'", doc2.Fields[1].Name())
+	}
+	if doc2.Fields[2].Name() != "Alternate2.Name" {
+		t.Errorf("expected field named 'Alternate2.Name', got '%s'", doc2.Fields[2].Name())
+	}
+	if doc2.Fields[3].Name() != "Alternate3" {
+		t.Errorf("expected field named 'Alternate3', got '%s'", doc2.Fields[3].Name())
+	}
+}
+
+func TestAnonymousStructFieldWithJSONStructTagEmptString(t *testing.T) {
+	type InterfaceThing interface{}
+	type Thing struct {
+		InterfaceThing `json:""`
+	}
+
+	x := Thing{
+		InterfaceThing: map[string]interface{}{
+			"key": "value",
+		},
+	}
+
+	doc := document.NewDocument("1")
+	m := NewIndexMapping()
+	err := m.mapDocument(doc, x)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(doc.Fields) != 1 {
+		t.Fatalf("expected 1 field, got %d", len(doc.Fields))
+	}
+	if doc.Fields[0].Name() != "key" {
+		t.Errorf("expected field named 'key', got '%s'", doc.Fields[0].Name())
+	}
+}