bind: add support of multipart multi files

bind.go

@@ -8,6 +8,7 @@ import (
 	"encoding/xml"
 	"errors"
 	"fmt"
+	"mime/multipart"
 	"net/http"
 	"reflect"
 	"strconv"
@@ -90,7 +91,7 @@ func (b *DefaultBinder) BindBody(c Context, i interface{}) (err error) {
 			}
 			return NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
 		}
-	case strings.HasPrefix(ctype, MIMEApplicationForm), strings.HasPrefix(ctype, MIMEMultipartForm):
+	case strings.HasPrefix(ctype, MIMEApplicationForm):
 		params, err := c.FormParams()
 		if err != nil {
 			return NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
@@ -98,6 +99,14 @@ func (b *DefaultBinder) BindBody(c Context, i interface{}) (err error) {
 		if err = b.bindData(i, params, "form"); err != nil {
 			return NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
 		}
+	case strings.HasPrefix(ctype, MIMEMultipartForm):
+		params, err := c.MultipartForm()
+		if err != nil {
+			return NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
+		}
+		if err = b.bindData(i, params.Value, "form", params.File); err != nil {
+			return NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
+		}
 	default:
 		return ErrUnsupportedMediaType
 	}
@@ -132,8 +141,8 @@ func (b *DefaultBinder) Bind(i interface{}, c Context) (err error) {
 }
 
 // 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 {
+func (b *DefaultBinder) bindData(destination interface{}, data map[string][]string, tag string, files ...map[string][]*multipart.FileHeader) error {
+	if destination == nil || (len(data) == 0 && len(files) == 0) {
 		return nil
 	}
 	typ := reflect.TypeOf(destination).Elem()
@@ -209,6 +218,37 @@ func (b *DefaultBinder) bindData(destination interface{}, data map[string][]stri
 			continue
 		}
 
+		// Handle multiple file uploads ([]*multipart.FileHeader, *multipart.FileHeader, []multipart.FileHeader)
+		if len(files) > 0 {
+			for _, fileMap := range files {
+				fileHeaders, exists := fileMap[inputFieldName]
+				if exists {
+					if structField.Type() == reflect.TypeOf([]*multipart.FileHeader(nil)) {
+						structField.Set(reflect.ValueOf(fileHeaders))
+						continue
+					} else if structField.Type() == reflect.TypeOf([]multipart.FileHeader(nil)) {
+						var headers []multipart.FileHeader
+						for _, fileHeader := range fileHeaders {
+							headers = append(headers, *fileHeader)
+						}
+						structField.Set(reflect.ValueOf(headers))
+						continue
+					} else if structField.Type() == reflect.TypeOf(&multipart.FileHeader{}) {
+
+						if len(fileHeaders) > 0 {
+							structField.Set(reflect.ValueOf(fileHeaders[0]))
+						}
+						continue
+					} else if structField.Type() == reflect.TypeOf(multipart.FileHeader{}) {
+						if len(fileHeaders) > 0 {
+							structField.Set(reflect.ValueOf(*fileHeaders[0]))
+						}
+						continue
+					}
+				}
+			}
+		}
+
 		inputValue, exists := data[inputFieldName]
 		if !exists {
 			// Go json.Unmarshal supports case insensitive binding.  However the

bind_test.go

@@ -1102,6 +1102,103 @@ func TestDefaultBinder_BindBody(t *testing.T) {
 	}
 }
 
+type testFile struct {
+	Fieldname string
+	Filename  string
+	Content   []byte
+}
+
+// createRequestMultipartFiles creates a multipart HTTP request with multiple files.
+func createRequestMultipartFiles(t *testing.T, files ...testFile) *http.Request {
+	var body bytes.Buffer
+	mw := multipart.NewWriter(&body)
+
+	for _, file := range files {
+		fw, err := mw.CreateFormFile(file.Fieldname, file.Filename)
+		assert.NoError(t, err)
+
+		n, err := fw.Write(file.Content)
+		assert.NoError(t, err)
+		assert.Equal(t, len(file.Content), n)
+	}
+
+	err := mw.Close()
+	assert.NoError(t, err)
+
+	req, err := http.NewRequest(http.MethodPost, "/", &body)
+	assert.NoError(t, err)
+
+	req.Header.Set("Content-Type", mw.FormDataContentType())
+
+	return req
+}
+
+func assertMultipartFileHeader(t *testing.T, fh *multipart.FileHeader, file testFile) {
+	assert.Equal(t, file.Filename, fh.Filename)
+	assert.Equal(t, int64(len(file.Content)), fh.Size)
+	fl, err := fh.Open()
+	assert.NoError(t, err)
+	body, err := io.ReadAll(fl)
+	assert.NoError(t, err)
+	assert.Equal(t, string(file.Content), string(body))
+	err = fl.Close()
+	assert.NoError(t, err)
+}
+
+func TestFormMultipartBindTwoFiles(t *testing.T) {
+	var args struct {
+		Files []*multipart.FileHeader `form:"files"`
+	}
+
+	files := []testFile{
+		{
+			Fieldname: "files",
+			Filename:  "file1.txt",
+			Content:   []byte("This is the content of file 1."),
+		},
+		{
+			Fieldname: "files",
+			Filename:  "file2.txt",
+			Content:   []byte("This is the content of file 2."),
+		},
+	}
+
+	e := New()
+	req := createRequestMultipartFiles(t, files...)
+	rec := httptest.NewRecorder()
+	c := e.NewContext(req, rec)
+
+	err := c.Bind(&args)
+	assert.NoError(t, err)
+
+	assert.Len(t, args.Files, len(files))
+	for idx, file := range files {
+		assertMultipartFileHeader(t, args.Files[idx], file)
+	}
+}
+
+func TestFormMultipartBindOneFile(t *testing.T) {
+	var args struct {
+		File *multipart.FileHeader `form:"file"`
+	}
+
+	file := testFile{
+		Fieldname: "file",
+		Filename:  "file1.txt",
+		Content:   []byte("This is the content of file 1."),
+	}
+
+	e := New()
+	req := createRequestMultipartFiles(t, file)
+	rec := httptest.NewRecorder()
+	c := e.NewContext(req, rec)
+
+	err := c.Bind(&args)
+	assert.NoError(t, err)
+
+	assertMultipartFileHeader(t, args.File, file)
+}
+
 func testBindURL(queryString string, target any) error {
 	e := New()
 	req := httptest.NewRequest(http.MethodGet, queryString, nil)