add Encoder + Decoder Mode setting to allow Implicit, the default, or Explicit decoding or encoding

Author: Dean Karn

cache.go

@@ -44,7 +44,7 @@ func (s *structCacheMap) Set(key reflect.Type, value *cachedStruct) {
 	s.m.Store(nm)
 }
 
-func (s *structCacheMap) parseStruct(current reflect.Value, key reflect.Type, tagName string) *cachedStruct {
+func (s *structCacheMap) parseStruct(mode Mode, current reflect.Value, key reflect.Type, tagName string) *cachedStruct {
 
 	s.lock.Lock()
 
@@ -76,6 +76,10 @@ func (s *structCacheMap) parseStruct(current reflect.Value, key reflect.Type, ta
 			continue
 		}
 
+		if mode == ModeExplicit && len(name) == 0 {
+			continue
+		}
+
 		if len(name) == 0 {
 			name = fld.Name
 		}

cache_test.go

@@ -43,7 +43,7 @@ func TestDecoderMultipleSimultaniousParseStructRequests(t *testing.T) {
 	for i := 0; i < 200; i++ {
 		go func() {
 			<-proceed
-			s := sc.parseStruct(sv, typ, "form")
+			s := sc.parseStruct(ModeImplicit, sv, typ, "form")
 			NotEqual(t, s, nil)
 		}()
 	}

decoder.go

@@ -149,7 +149,7 @@ func (d *decoder) traverseStruct(v reflect.Value, typ reflect.Type, namespace []
 	// including tags
 	s, ok := d.d.structCache.Get(typ)
 	if !ok {
-		s = d.d.structCache.parseStruct(v, typ, d.d.tagName)
+		s = d.d.structCache.parseStruct(d.d.mode, v, typ, d.d.tagName)
 	}
 
 	for _, f := range s.fields {

decoder_test.go

@@ -1428,3 +1428,26 @@ func TestDecoderPointerToPointer(t *testing.T) {
 	Equal(t, err, nil)
 	Equal(t, tst.Value, "testVal")
 }
+
+func TestDecoderExplicit(t *testing.T) {
+
+	type Test struct {
+		Name string `form:"Name"`
+		Age  int
+	}
+
+	values := map[string][]string{
+		"Name": {"Joeybloggs"},
+		"Age":  {"3"},
+	}
+
+	var test Test
+
+	d := NewDecoder()
+	d.SetMode(ModeExplicit)
+
+	err := d.Decode(&test, values)
+	Equal(t, err, nil)
+	Equal(t, test.Name, "Joeybloggs")
+	Equal(t, test.Age, 0)
+}

encoder.go

@@ -45,7 +45,7 @@ func (e *encoder) traverseStruct(v reflect.Value, namespace []byte, idx int) {
 	// including tags
 	s, ok := e.e.structCache.Get(typ)
 	if !ok {
-		s = e.e.structCache.parseStruct(v, typ, e.e.tagName)
+		s = e.e.structCache.parseStruct(e.e.mode, v, typ, e.e.tagName)
 	}
 
 	for _, f := range s.fields {

encoder_test.go

@@ -1234,3 +1234,24 @@ func TestEncoderPanicsAndBadValues(t *testing.T) {
 	Equal(t, ok, true)
 	Equal(t, err.Error(), "form: Encode(nil *form.TestStruct)")
 }
+
+func TestEncoderExplicit(t *testing.T) {
+
+	type Test struct {
+		Name string `form:"Name"`
+		Age  int
+	}
+
+	test := &Test{
+		Name: "Joeybloggs",
+		Age:  3,
+	}
+
+	encoder := NewEncoder()
+	encoder.SetMode(ModeExplicit)
+
+	values, err := encoder.Encode(test)
+	Equal(t, err, nil)
+	Equal(t, len(values), 1)
+	Equal(t, values["Name"][0], "Joeybloggs")
+}

form.go

@@ -16,3 +16,17 @@ const (
 var (
 	timeType = reflect.TypeOf(time.Time{})
 )
+
+// Mode specifies which mode the form decoder is to run
+type Mode uint8
+
+const (
+
+	// ModeImplicit tries to parse values for all
+	// fields that do not have an ignore '-' tag
+	ModeImplicit Mode = iota
+
+	// ModeExplicit only parses values for field with a field tag
+	// and that tag is not the ignore '-' tag
+	ModeExplicit
+)

form_decoder.go

@@ -64,6 +64,7 @@ type dataMap []*recursiveData
 // Decoder is the main decode instance
 type Decoder struct {
 	tagName         string
+	mode            Mode
 	structCache     *structCacheMap
 	customTypeFuncs map[reflect.Type]DecodeCustomTypeFunc
 	maxArraySize    int
@@ -75,6 +76,7 @@ func NewDecoder() *Decoder {
 
 	d := &Decoder{
 		tagName:      "form",
+		mode:         ModeImplicit,
 		structCache:  newStructCacheMap(),
 		maxArraySize: 10000,
 	}
@@ -95,6 +97,12 @@ func (d *Decoder) SetTagName(tagName string) {
 	d.tagName = tagName
 }
 
+// SetMode sets the mode the decoder should run
+// Default is ModeImplicit
+func (d *Decoder) SetMode(mode Mode) {
+	d.mode = mode
+}
+
 // SetMaxArraySize sets maximum array size that can be created.
 // This limit is for the array indexing this library supports to
 // avoid potential DOS or man-in-the-middle attacks using an unusually

form_encoder.go

@@ -45,6 +45,7 @@ func (e *InvalidEncodeError) Error() string {
 // Encoder is the main encode instance
 type Encoder struct {
 	tagName         string
+	mode            Mode
 	structCache     *structCacheMap
 	customTypeFuncs map[reflect.Type]EncodeCustomTypeFunc
 	dataPool        *sync.Pool
@@ -55,6 +56,7 @@ func NewEncoder() *Encoder {
 
 	e := &Encoder{
 		tagName:     "form",
+		mode:        ModeImplicit,
 		structCache: newStructCacheMap(),
 	}
 
@@ -68,12 +70,18 @@ func NewEncoder() *Encoder {
 	return e
 }
 
-// SetTagName sets the given tag name to be used by the decoder.
+// SetTagName sets the given tag name to be used by the encoder.
 // Default is "form"
 func (e *Encoder) SetTagName(tagName string) {
 	e.tagName = tagName
 }
 
+// SetMode sets the mode the encoder should run
+// Default is ModeImplicit
+func (e *Encoder) SetMode(mode Mode) {
+	e.mode = mode
+}
+
 // RegisterCustomTypeFunc registers a CustomTypeFunc against a number of types
 // NOTE: this method is not thread-safe it is intended that these all be registered prior to any parsing
 func (e *Encoder) RegisterCustomTypeFunc(fn EncodeCustomTypeFunc, types ...interface{}) {