From 24f3e1df2f5ffab5696aaa95cf0b8dea167ef084 Mon Sep 17 00:00:00 2001
From: n3wtron <n3wtron@users.noreply.github.com>
Date: Tue, 10 May 2016 14:09:22 +0200
Subject: [PATCH] created flatnested tag to convert the anonymous field in a
 flat map (#46)

* flat fields with the new flatten tag
* added flatten tag documentation
---
 structs.go      | 17 ++++++++++++++--
 structs_test.go | 54 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/structs.go b/structs.go
index 408d50f..b88ec62 100644
--- a/structs.go
+++ b/structs.go
@@ -52,6 +52,12 @@ func New(s interface{}) *Struct {
 //   // Map will panic if Animal does not implement String().
 //   Field *Animal `structs:"field,string"`
 //
+// A tag value with the option of "flatten" used in a struct field is to flatten its fields
+// in the output map. Example:
+//
+//   // The FieldStruct's fields will be flattened into the output map.
+//   FieldStruct time.Time `structs:"flatten"`
+//
 // A tag value with the option of "omitnested" stops iterating further if the type
 // is a struct. Example:
 //
@@ -90,7 +96,7 @@ func (s *Struct) FillMap(out map[string]interface{}) {
 	for _, field := range fields {
 		name := field.Name
 		val := s.value.FieldByName(name)
-
+		isSubStruct := false
 		var finalVal interface{}
 
 		tagName, tagOpts := parseTag(field.Tag.Get(s.TagName))
@@ -115,6 +121,7 @@ func (s *Struct) FillMap(out map[string]interface{}) {
 			n := New(val.Interface())
 			n.TagName = s.TagName
 			m := n.Map()
+			isSubStruct = true
 			if len(m) == 0 {
 				finalVal = val.Interface()
 			} else {
@@ -132,7 +139,13 @@ func (s *Struct) FillMap(out map[string]interface{}) {
 			continue
 		}
 
-		out[name] = finalVal
+		if isSubStruct && (tagOpts.Has("flatten")) {
+			for k := range finalVal.(map[string]interface{}) {
+				out[k] = finalVal.(map[string]interface{})[k]
+			}
+		} else {
+			out[name] = finalVal
+		}
 	}
 }
 
diff --git a/structs_test.go b/structs_test.go
index 30e3115..d7ea11d 100644
--- a/structs_test.go
+++ b/structs_test.go
@@ -296,6 +296,60 @@ func TestMap_Anonymous(t *testing.T) {
 	}
 }
 
+func TestMap_Flatnested(t *testing.T) {
+	type A struct {
+		Name string
+	}
+	a := A{Name: "example"}
+
+	type B struct {
+		A `structs:",flatten"`
+		C int
+	}
+	b := &B{C: 123}
+	b.A = a
+
+	m := Map(b)
+
+	_, ok := m["A"].(map[string]interface{})
+	if ok {
+		t.Error("Embedded A struct with tag flatten has to be flat in the map")
+	}
+
+	expectedMap := map[string]interface{}{"Name": "example", "C": 123}
+	if !reflect.DeepEqual(m, expectedMap) {
+		t.Errorf("The exprected map %+v does't correspond to %+v", expectedMap, m)
+	}
+
+}
+
+func TestMap_FlatnestedOverwrite(t *testing.T) {
+	type A struct {
+		Name string
+	}
+	a := A{Name: "example"}
+
+	type B struct {
+		A    `structs:",flatten"`
+		Name string
+		C    int
+	}
+	b := &B{C: 123, Name: "bName"}
+	b.A = a
+
+	m := Map(b)
+
+	_, ok := m["A"].(map[string]interface{})
+	if ok {
+		t.Error("Embedded A struct with tag flatten has to be flat in the map")
+	}
+
+	expectedMap := map[string]interface{}{"Name": "bName", "C": 123}
+	if !reflect.DeepEqual(m, expectedMap) {
+		t.Errorf("The exprected map %+v does't correspond to %+v", expectedMap, m)
+	}
+}
+
 func TestMap_TimeField(t *testing.T) {
 	type A struct {
 		CreatedAt time.Time