feat: allow custom unmarshalers for form binding: json/text/binary

binding/form_mapping.go

@@ -197,6 +197,18 @@ func setByForm(value reflect.Value, field reflect.StructField, form map[string][
 	}
 }
 
+type jsonUnmarshaler interface {
+	UnmarshalJSON([]byte) error
+}
+
+type textUnmarshaler interface {
+	UnmarshalText([]byte) error
+}
+
+type binaryUnmarshaler interface {
+	UnmarshalBinary([]byte) error
+}
+
 func setWithProperType(val string, value reflect.Value, field reflect.StructField) error {
 	switch value.Kind() {
 	case reflect.Int:
@@ -236,6 +248,15 @@ func setWithProperType(val string, value reflect.Value, field reflect.StructFiel
 		case time.Time:
 			return setTimeField(val, field, value)
 		}
+		if unmarshaler, ok := value.Addr().Interface().(jsonUnmarshaler); ok {
+			return unmarshaler.UnmarshalJSON(bytesconv.StringToBytes(val))
+		}
+		if unmarshaler, ok := value.Addr().Interface().(textUnmarshaler); ok {
+			return unmarshaler.UnmarshalText(bytesconv.StringToBytes(val))
+		}
+		if unmarshaler, ok := value.Addr().Interface().(binaryUnmarshaler); ok {
+			return unmarshaler.UnmarshalBinary(bytesconv.StringToBytes(val))
+		}
 		return json.Unmarshal(bytesconv.StringToBytes(val), value.Addr().Interface())
 	case reflect.Map:
 		return json.Unmarshal(bytesconv.StringToBytes(val), value.Addr().Interface())

binding/form_mapping_test.go

@@ -5,7 +5,9 @@
 package binding
 
 import (
+	"errors"
 	"reflect"
+	"strings"
 	"testing"
 	"time"
 
@@ -288,3 +290,93 @@ func TestMappingIgnoredCircularRef(t *testing.T) {
 	err := mappingByPtr(&s, formSource{}, "form")
 	assert.NoError(t, err)
 }
+
+// this structure has special json unmarshaller, in order to parse email (as an example) as specific structure
+type withJsonUnmarshaller struct {
+	Name string
+	Host string
+}
+
+func (o *withJsonUnmarshaller) UnmarshalJSON(data []byte) error {
+	elems := strings.Split(string(data), "@")
+	if len(elems) != 2 {
+		return errors.New("cannot parse %q as email")
+	}
+	o.Name = elems[0]
+	o.Host = elems[1]
+	return nil
+}
+
+func TestMappingStructFieldJSONUnmarshaller(t *testing.T) {
+	var s struct {
+		Email withJsonUnmarshaller
+	}
+
+	err := mappingByPtr(&s, formSource{"Email": {`test@example.org`}}, "form")
+	assert.NoError(t, err)
+	assert.Equal(t, "test", s.Email.Name)
+	assert.Equal(t, "example.org", s.Email.Host)
+
+	err = mappingByPtr(&s, formSource{"Email": {`not an email`}}, "form")
+	assert.Error(t, err)
+}
+
+// this structure has special text unmarshaller, in order to parse email (as an example) as specific structure
+type withTextUnmarshaller struct {
+	Name string
+	Host string
+}
+
+func (o *withTextUnmarshaller) UnmarshalText(data []byte) error {
+	elems := strings.Split(string(data), "@")
+	if len(elems) != 2 {
+		return errors.New("cannot parse %q as email")
+	}
+	o.Name = elems[0]
+	o.Host = elems[1]
+	return nil
+}
+
+func TestMappingStructFieldTextUnmarshaller(t *testing.T) {
+	var s struct {
+		Email withTextUnmarshaller
+	}
+
+	err := mappingByPtr(&s, formSource{"Email": {`test@example.org`}}, "form")
+	assert.NoError(t, err)
+	assert.Equal(t, "test", s.Email.Name)
+	assert.Equal(t, "example.org", s.Email.Host)
+
+	err = mappingByPtr(&s, formSource{"Email": {`not an email`}}, "form")
+	assert.Error(t, err)
+}
+
+// this structure has special binary unmarshaller, in order to parse email (as an example) as specific structure
+type withBinaryUnmarshaller struct {
+	Name string
+	Host string
+}
+
+func (o *withBinaryUnmarshaller) UnmarshalBinary(data []byte) error {
+	elems := strings.Split(string(data), "@")
+	if len(elems) != 2 {
+		return errors.New("cannot parse %q as email")
+	}
+	o.Name = elems[0]
+	o.Host = elems[1]
+	return nil
+}
+
+func TestMappingStructFieldBinaryUnmarshaller(t *testing.T) {
+	var s struct {
+		Email withBinaryUnmarshaller
+	}
+
+	err := mappingByPtr(&s, formSource{"Email": {`test@example.org`}}, "form")
+	assert.NoError(t, err)
+	assert.Equal(t, "test", s.Email.Name)
+	assert.Equal(t, "example.org", s.Email.Host)
+
+	err = mappingByPtr(&s, formSource{"Email": {`not an email`}}, "form")
+	assert.Error(t, err)
+}

docs/doc.md

@@ -57,6 +57,7 @@
   - [Bind form-data request with custom struct](#bind-form-data-request-with-custom-struct)
   - [Try to bind body into different structs](#try-to-bind-body-into-different-structs)
   - [Bind form-data request with custom struct and custom tag](#bind-form-data-request-with-custom-struct-and-custom-tag)
+  - [Bind Query with custom unmarshalers](#bind-query-with-custom-unmarshalers)
   - [http2 server push](#http2-server-push)
   - [Define format for the log of routes](#define-format-for-the-log-of-routes)
   - [Set and get a cookie](#set-and-get-a-cookie)
@@ -2002,6 +2003,59 @@ func ListHandler(s *Service) func(ctx *gin.Context) {
 }
 ```
 
+### Bind Query with custom unmarshalers
+
+Any structure that has custom `UnmarshalJSON` or `UnmarshalText` or `UnmarshalBinary` can be used to parse input as necessary
+
+```go
+package main
+import (
+  "fmt"
+  "net/http"
+  "strings"
+  "github.com/gin-gonic/gin"
+)
+// Booking contains data binded using custom unmarshaler.
+type Payload struct {
+  Email  EmailDetails `form:"email"`
+}
+// this structure has special json unmarshaller, in order to parse email (as an example) as specific structure
+type EmailDetails struct {
+  Name string
+  Host string
+}
+func (o *EmailDetails) UnmarshalJSON(data []byte) error {
+  elems := strings.Split(string(data), "@")
+  if len(elems) != 2 {
+    return fmt.Errorf("cannot parse %q as email", string(data))
+  }
+  o.Name = elems[0]
+  o.Host = elems[1]
+  return nil
+}
+func main() {
+  route := gin.Default()
+  route.GET("/email", getEmail)
+  route.Run(":8085")
+}
+func getEmail(c *gin.Context) {
+  var p Payload
+  if err := c.ShouldBindQuery(&p); err == nil {
+    c.JSON(http.StatusOK, gin.H{"message": "Email information is correct"})
+  } else {
+    c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+  }
+}
+```
+
+```console
+$ curl "localhost:8085/email?email=test@example.org"
+{"message":"Email information is correct"}
+
+$ curl "localhost:8085/email?email=test-something-else"
+{"error":"cannot parse \"test-something-else\" as email"}
+```
+
 ### http2 server push
 
 http.Pusher is supported only **go1.8+**. See the [golang blog](https://go.dev/blog/h2push) for detail information.