Fix #1729 Binding query/path params and form fields to struct only works for explicit tags (#1734)

* Binding query/path params and form fields to struct only works for fields that have explicit TAG defined on struct
* remove unnecessary benchmark after change because it is not valid test anymore

bind.go

@@ -116,12 +116,13 @@ func (b *DefaultBinder) Bind(i interface{}, c Context) (err error) {
 	return b.BindBody(c, i)
 }
 
-func (b *DefaultBinder) bindData(ptr interface{}, data map[string][]string, tag string) error {
-	if ptr == nil || len(data) == 0 {
+// bindData will bind data ONLY fields in destination struct that have EXPLICIT tag
+func (b *DefaultBinder) bindData(destination interface{}, data map[string][]string, tag string) error {
+	if destination == nil || len(data) == 0 {
 		return nil
 	}
-	typ := reflect.TypeOf(ptr).Elem()
-	val := reflect.ValueOf(ptr).Elem()
+	typ := reflect.TypeOf(destination).Elem()
+	val := reflect.ValueOf(destination).Elem()
 
 	// Map
 	if typ.Kind() == reflect.Map {
@@ -146,14 +147,15 @@ func (b *DefaultBinder) bindData(ptr interface{}, data map[string][]string, tag
 		inputFieldName := typeField.Tag.Get(tag)
 
 		if inputFieldName == "" {
-			inputFieldName = typeField.Name
-			// If tag is nil, we inspect if the field is a struct.
+			// If tag is nil, we inspect if the field is a not BindUnmarshaler struct and try to bind data into it (might contains fields with tags).
+			// structs that implement BindUnmarshaler are binded only when they have explicit tag
 			if _, ok := structField.Addr().Interface().(BindUnmarshaler); !ok && structFieldKind == reflect.Struct {
 				if err := b.bindData(structField.Addr().Interface(), data, tag); err != nil {
 					return err
 				}
-				continue
 			}
+			// does not have explicit tag and is not an ordinary struct - so move to next field
+			continue
 		}
 
 		inputValue, exists := data[inputFieldName]

bind_test.go

@@ -160,6 +160,31 @@ var values = map[string][]string{
 	"ST":      {"bar"},
 }
 
+func TestToMultipleFields(t *testing.T) {
+	e := New()
+	req := httptest.NewRequest(http.MethodGet, "/?id=1&ID=2", nil)
+	rec := httptest.NewRecorder()
+	c := e.NewContext(req, rec)
+
+	type Root struct {
+		ID     int64 `query:"id"`
+		Child2 struct {
+			ID int64
+		}
+		Child1 struct {
+			ID int64 `query:"id"`
+		}
+	}
+
+	u := new(Root)
+	err := c.Bind(u)
+	if assert.NoError(t, err) {
+		assert.Equal(t, int64(1), u.ID)        // perfectly reasonable
+		assert.Equal(t, int64(1), u.Child1.ID) // untagged struct containing tagged field gets filled (by tag)
+		assert.Equal(t, int64(0), u.Child2.ID) // untagged struct containing untagged field should not be bind
+	}
+}
+
 func TestBindJSON(t *testing.T) {
 	assert := assert.New(t)
 	testBindOkay(assert, strings.NewReader(userJSON), MIMEApplicationJSON)
@@ -242,6 +267,9 @@ func TestBindUnmarshalParam(t *testing.T) {
 		TA        []Timestamp `query:"ta"`
 		SA        StringArray `query:"sa"`
 		ST        Struct
+		StWithTag struct {
+			Foo string `query:"st"`
+		}
 	}{}
 	err := c.Bind(&result)
 	ts := Timestamp(time.Date(2016, 12, 6, 19, 9, 5, 0, time.UTC))
@@ -252,7 +280,8 @@ func TestBindUnmarshalParam(t *testing.T) {
 		assert.Equal(ts, result.T)
 		assert.Equal(StringArray([]string{"one", "two", "three"}), result.SA)
 		assert.Equal([]Timestamp{ts, ts}, result.TA)
-		assert.Equal(Struct{"baz"}, result.ST)
+		assert.Equal(Struct{""}, result.ST)       // child struct does not have a field with matching tag
+		assert.Equal("baz", result.StWithTag.Foo) // child struct has field with matching tag
 	}
 }
 
@@ -274,7 +303,7 @@ func TestBindUnmarshalText(t *testing.T) {
 		assert.Equal(t, ts, result.T)
 		assert.Equal(t, StringArray([]string{"one", "two", "three"}), result.SA)
 		assert.Equal(t, []time.Time{ts, ts}, result.TA)
-		assert.Equal(t, Struct{"baz"}, result.ST)
+		assert.Equal(t, Struct{""}, result.ST) // field in child struct does not have tag
 	}
 }
 
@@ -323,11 +352,27 @@ func TestBindUnsupportedMediaType(t *testing.T) {
 }
 
 func TestBindbindData(t *testing.T) {
-	assert := assert.New(t)
+	a := assert.New(t)
 	ts := new(bindTestStruct)
 	b := new(DefaultBinder)
-	b.bindData(ts, values, "form")
-	assertBindTestStruct(assert, ts)
+	err := b.bindData(ts, values, "form")
+	a.NoError(err)
+
+	a.Equal(0, ts.I)
+	a.Equal(int8(0), ts.I8)
+	a.Equal(int16(0), ts.I16)
+	a.Equal(int32(0), ts.I32)
+	a.Equal(int64(0), ts.I64)
+	a.Equal(uint(0), ts.UI)
+	a.Equal(uint8(0), ts.UI8)
+	a.Equal(uint16(0), ts.UI16)
+	a.Equal(uint32(0), ts.UI32)
+	a.Equal(uint64(0), ts.UI64)
+	a.Equal(false, ts.B)
+	a.Equal(float32(0), ts.F32)
+	a.Equal(float64(0), ts.F64)
+	a.Equal("", ts.S)
+	a.Equal("", ts.cantSet)
 }
 
 func TestBindParam(t *testing.T) {
@@ -470,20 +515,6 @@ func TestBindSetFields(t *testing.T) {
 	}
 }
 
-func BenchmarkBindbindData(b *testing.B) {
-	b.ReportAllocs()
-	assert := assert.New(b)
-	ts := new(bindTestStruct)
-	binder := new(DefaultBinder)
-	var err error
-	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
-		err = binder.bindData(ts, values, "form")
-	}
-	assert.NoError(err)
-	assertBindTestStruct(assert, ts)
-}
-
 func BenchmarkBindbindDataWithTags(b *testing.B) {
 	b.ReportAllocs()
 	assert := assert.New(b)
@@ -560,8 +591,9 @@ func TestDefaultBinder_BindToStructFromMixedSources(t *testing.T) {
 	// these tests are to document this behaviour and detect further possible regressions when bind implementation is changed
 
 	type Opts struct {
-		ID   int    `json:"id"`
-		Node string `json:"node"`
+		ID   int    `json:"id" form:"id" query:"id"`
+		Node string `json:"node" form:"node" query:"node" param:"node"`
+		Lang string
 	}
 
 	var testCases = []struct {
@@ -727,8 +759,8 @@ func TestDefaultBinder_BindBody(t *testing.T) {
 	// these tests are to document this behaviour and detect further possible regressions when bind implementation is changed
 
 	type Node struct {
-		ID   int    `json:"id" xml:"id"`
-		Node string `json:"node" xml:"node"`
+		ID   int    `json:"id" xml:"id" form:"id" query:"id"`
+		Node string `json:"node" xml:"node" form:"node" query:"node" param:"node"`
 	}
 	type Nodes struct {
 		Nodes []Node `xml:"node" form:"node"`
@@ -824,7 +856,7 @@ func TestDefaultBinder_BindBody(t *testing.T) {
 			expectError:      "code=400, message=Syntax error: line=1, error=XML syntax error on line 1: unexpected EOF, internal=XML syntax error on line 1: unexpected EOF",
 		},
 		{
-			name:             "ok, FORM POST bind to struct with: path + query + empty body",
+			name:             "ok, FORM POST bind to struct with: path + query + body",
 			givenURL:         "/api/real_node/endpoint?node=xxx",
 			givenMethod:      http.MethodPost,
 			givenContentType: MIMEApplicationForm,