Fix empty keyName when decoding struct -> map with omitempty

mapstructure.go

@@ -927,7 +927,9 @@ func (d *Decoder) decodeMapFromStruct(name string, dataVal reflect.Value, val re
  return fmt.Errorf("cannot squash non-struct type '%s'", v.Type())
  }
  }
- keyName = tagValue[:index]
+ if keyNameTagValue := tagValue[:index]; keyNameTagValue != "" {
+ keyName = keyNameTagValue
+ }
  } else if len(tagValue) > 0 {
  if tagValue == "-" {
  continue

mapstructure_bugs_test.go

@@ -1,6 +1,7 @@
 package mapstructure
 
 import (
+ "fmt"
  "reflect"
  "testing"
  "time"
@@ -601,3 +602,25 @@ func TestMapSquash(t *testing.T) {
  t.Fatal("expected false")
  }
 }
+
+// GH-238: Empty key name when decoding map from struct with only omitempty flag
+func TestMapOmitEmptyWithEmptyFieldnameInTag(t *testing.T) {
+ type Struct struct {
+ Username string `mapstructure:",omitempty"`
+ Age int `mapstructure:",omitempty"`
+ }
+
+ s := Struct{
+ Username: "Joe",
+ }
+ var m map[string]interface{}
+
+ if err := Decode(s, &m); err != nil {
+ t.Fatal(err)
+ }
+
+ expect := "map[Username:Joe]"
+ if got := fmt.Sprintf("%+v", m); expect != got {
+ t.Fatalf("expect %q, got: %s", expect, got)
+ }
+}