feat(binding): Support custom BindUnmarshaler for binding.

binding/form_mapping.go

@@ -165,6 +165,23 @@ func tryToSetValue(value reflect.Value, field reflect.StructField, setter setter
 	return setter.TrySet(value, field, tagValue, setOpt)
 }
 
+// BindUnmarshaler is the interface used to wrap the UnmarshalParam method.
+type BindUnmarshaler interface {
+	// UnmarshalParam decodes and assigns a value from an form or query param.
+	UnmarshalParam(param string) error
+}
+
+// trySetCustom tries to set a custom type value
+// If the value implements the BindUnmarshaler interface, it will be used to set the value, we will return `true`
+// to skip the default value setting.
+func trySetCustom(val string, value reflect.Value) (isSet bool, err error) {
+	switch v := value.Addr().Interface().(type) {
+	case BindUnmarshaler:
+		return true, v.UnmarshalParam(val)
+	}
+	return false, nil
+}
+
 func setByForm(value reflect.Value, field reflect.StructField, form map[string][]string, tagValue string, opt setOptions) (isSet bool, err error) {
 	vs, ok := form[tagValue]
 	if !ok && !opt.isDefaultExists {
@@ -194,6 +211,9 @@ func setByForm(value reflect.Value, field reflect.StructField, form map[string][
 		if len(vs) > 0 {
 			val = vs[0]
 		}
+		if ok, err := trySetCustom(val, value); ok {
+			return ok, err
+		}
 		return true, setWithProperType(val, value, field)
 	}
 }

binding/form_mapping_test.go

@@ -5,8 +5,11 @@
 package binding
 
 import (
+	"fmt"
 	"mime/multipart"
 	"reflect"
+	"strconv"
+	"strings"
 	"testing"
 	"time"
 
@@ -323,3 +326,99 @@ func TestMappingIgnoredCircularRef(t *testing.T) {
 	err := mappingByPtr(&s, formSource{}, "form")
 	assert.NoError(t, err)
 }
+
+type customUnmarshalParamHex int
+
+func (f *customUnmarshalParamHex) UnmarshalParam(param string) error {
+	v, err := strconv.ParseInt(param, 16, 64)
+	if err != nil {
+		return err
+	}
+	*f = customUnmarshalParamHex(v)
+	return nil
+}
+
+func TestMappingCustomUnmarshalParamHexWithFormTag(t *testing.T) {
+	var s struct {
+		Foo customUnmarshalParamHex `form:"foo"`
+	}
+	err := mappingByPtr(&s, formSource{"foo": {`f5`}}, "form")
+	assert.NoError(t, err)
+
+	assert.EqualValues(t, 245, s.Foo)
+}
+
+func TestMappingCustomUnmarshalParamHexWithURITag(t *testing.T) {
+	var s struct {
+		Foo customUnmarshalParamHex `uri:"foo"`
+	}
+	err := mappingByPtr(&s, formSource{"foo": {`f5`}}, "uri")
+	assert.NoError(t, err)
+
+	assert.EqualValues(t, 245, s.Foo)
+}
+
+type customUnmarshalParamType struct {
+	Protocol string
+	Path     string
+	Name     string
+}
+
+func (f *customUnmarshalParamType) UnmarshalParam(param string) error {
+	parts := strings.Split(param, ":")
+	if len(parts) != 3 {
+		return fmt.Errorf("invalid format")
+	}
+	f.Protocol = parts[0]
+	f.Path = parts[1]
+	f.Name = parts[2]
+	return nil
+}
+
+func TestMappingCustomStructTypeWithFormTag(t *testing.T) {
+	var s struct {
+		FileData customUnmarshalParamType `form:"data"`
+	}
+	err := mappingByPtr(&s, formSource{"data": {`file:/foo:happiness`}}, "form")
+	assert.NoError(t, err)
+
+	assert.EqualValues(t, "file", s.FileData.Protocol)
+	assert.EqualValues(t, "/foo", s.FileData.Path)
+	assert.EqualValues(t, "happiness", s.FileData.Name)
+}
+
+func TestMappingCustomStructTypeWithURITag(t *testing.T) {
+	var s struct {
+		FileData customUnmarshalParamType `uri:"data"`
+	}
+	err := mappingByPtr(&s, formSource{"data": {`file:/foo:happiness`}}, "uri")
+	assert.NoError(t, err)
+
+	assert.EqualValues(t, "file", s.FileData.Protocol)
+	assert.EqualValues(t, "/foo", s.FileData.Path)
+	assert.EqualValues(t, "happiness", s.FileData.Name)
+}
+
+func TestMappingCustomPointerStructTypeWithFormTag(t *testing.T) {
+	var s struct {
+		FileData *customUnmarshalParamType `form:"data"`
+	}
+	err := mappingByPtr(&s, formSource{"data": {`file:/foo:happiness`}}, "form")
+	assert.NoError(t, err)
+
+	assert.EqualValues(t, "file", s.FileData.Protocol)
+	assert.EqualValues(t, "/foo", s.FileData.Path)
+	assert.EqualValues(t, "happiness", s.FileData.Name)
+}
+
+func TestMappingCustomPointerStructTypeWithURITag(t *testing.T) {
+	var s struct {
+		FileData *customUnmarshalParamType `uri:"data"`
+	}
+	err := mappingByPtr(&s, formSource{"data": {`file:/foo:happiness`}}, "uri")
+	assert.NoError(t, err)
+
+	assert.EqualValues(t, "file", s.FileData.Protocol)
+	assert.EqualValues(t, "/foo", s.FileData.Path)
+	assert.EqualValues(t, "happiness", s.FileData.Name)
+}

docs/doc.md

@@ -27,6 +27,7 @@
   - [Only Bind Query String](#only-bind-query-string)
   - [Bind Query String or Post Data](#bind-query-string-or-post-data)
   - [Bind Uri](#bind-uri)
+  - [Bind custom unmarshaler](#bind-custom-unmarshaler)
   - [Bind Header](#bind-header)
   - [Bind HTML checkboxes](#bind-html-checkboxes)
   - [Multipart/Urlencoded binding](#multiparturlencoded-binding)
@@ -899,6 +900,46 @@ curl -v localhost:8088/thinkerou/987fbc97-4bed-5078-9f07-9141ba07c9f3
 curl -v localhost:8088/thinkerou/not-uuid
 ```
 
+### Bind custom unmarshaler
+
+```go
+package main
+
+import (
+  "github.com/gin-gonic/gin"
+  "strings"
+)
+
+type Birthday string
+
+func (b *Birthday) UnmarshalParam(param string) error {
+  *b = Birthday(strings.Replace(param, "-", "/", -1))
+  return nil
+}
+
+func main() {
+  route := gin.Default()
+  var request struct {
+    Birthday Birthday `form:"birthday"`
+  }
+  route.GET("/test", func(ctx *gin.Context) {
+    _ = ctx.BindQuery(&request)
+    ctx.JSON(200, request.Birthday)
+  })
+  route.Run(":8088")
+}
+```
+
+Test it with:
+
+```sh
+curl 'localhost:8088/test?birthday=2000-01-01'
+```
+Result
+```sh
+"2000/01/01"
+```
+
 ### Bind Header
 
 ```go

gin_test.go

@@ -14,6 +14,7 @@ import (
 	"net/http/httptest"
 	"reflect"
 	"strconv"
+	"strings"
 	"sync/atomic"
 	"testing"
 	"time"
@@ -730,3 +731,26 @@ func TestWithOptionFunc(t *testing.T) {
 	assertRoutePresent(t, routes, RouteInfo{Path: "/test1", Method: "GET", Handler: "github.com/gin-gonic/gin.handlerTest1"})
 	assertRoutePresent(t, routes, RouteInfo{Path: "/test2", Method: "GET", Handler: "github.com/gin-gonic/gin.handlerTest2"})
 }
+
+type Birthday string
+
+func (b *Birthday) UnmarshalParam(param string) error {
+	*b = Birthday(strings.Replace(param, "-", "/", -1))
+	return nil
+}
+
+func TestCustomUnmarshalStruct(t *testing.T) {
+	route := Default()
+	var request struct {
+		Birthday Birthday `form:"birthday"`
+	}
+	route.GET("/test", func(ctx *Context) {
+		_ = ctx.BindQuery(&request)
+		ctx.JSON(200, request.Birthday)
+	})
+	req := httptest.NewRequest("GET", "/test?birthday=2000-01-01", nil)
+	w := httptest.NewRecorder()
+	route.ServeHTTP(w, req)
+	assert.Equal(t, 200, w.Code)
+	assert.Equal(t, `"2000/01/01"`, w.Body.String())
+}