Support ordered form data (#391)

middleware.go

@@ -2,6 +2,7 @@ package req
 
 import (
 	"bytes"
+	"errors"
 	"io"
 	"mime/multipart"
 	"net/http"
@@ -124,17 +125,30 @@ func writeMultipartFormFile(w *multipart.Writer, file *FileUpload, r *Request) e
 
 func writeMultiPart(r *Request, w *multipart.Writer) {
 	defer w.Close() // close multipart to write tailer boundary
-	for k, vs := range r.FormData {
-		for _, v := range vs {
-			w.WriteField(k, v)
+	if len(r.FormData) > 0 {
+		for k, vs := range r.FormData {
+			for _, v := range vs {
+				w.WriteField(k, v)
+			}
+		}
+	} else if len(r.OrderedFormData) > 0 {
+		if len(r.OrderedFormData)%2 != 0 {
+			r.error = errBadOrderedFormData
+			return
+		}
+		maxIndex := len(r.OrderedFormData) - 2
+		for i := 0; i <= maxIndex; i += 2 {
+			key := r.OrderedFormData[i]
+			value := r.OrderedFormData[i+1]
+			w.WriteField(key, value)
 		}
 	}
 	for _, file := range r.uploadFiles {
 		writeMultipartFormFile(w, file, r)
 	}
 }
 
-func handleMultiPart(c *Client, r *Request) (err error) {
+func handleMultiPart(r *Request) (err error) {
 	if r.forceChunkedEncoding {
 		pr, pw := io.Pipe()
 		r.GetBody = func() (io.ReadCloser, error) {
@@ -164,6 +178,29 @@ func handleFormData(r *Request) {
 	r.SetBodyBytes([]byte(r.FormData.Encode()))
 }
 
+var errBadOrderedFormData = errors.New("bad ordered form data, the number of key-value pairs should be an even number")
+
+func handleOrderedFormData(r *Request) {
+	r.SetContentType(header.FormContentType)
+	if len(r.OrderedFormData)%2 != 0 {
+		r.error = errBadOrderedFormData
+		return
+	}
+	maxIndex := len(r.OrderedFormData) - 2
+	var buf strings.Builder
+	for i := 0; i <= maxIndex; i += 2 {
+		key := r.OrderedFormData[i]
+		value := r.OrderedFormData[i+1]
+		if buf.Len() > 0 {
+			buf.WriteByte('&')
+		}
+		buf.WriteString(url.QueryEscape(key))
+		buf.WriteByte('=')
+		buf.WriteString(url.QueryEscape(value))
+	}
+	r.SetBodyString(buf.String())
+}
+
 func handleMarshalBody(c *Client, r *Request) error {
 	ct := ""
 	if r.Headers != nil {
@@ -205,16 +242,20 @@ func parseRequestBody(c *Client, r *Request) (err error) {
 	}
 	// handle multipart
 	if r.isMultiPart {
-		return handleMultiPart(c, r)
+		return handleMultiPart(r)
 	}
 
 	// handle form data
 	if len(c.FormData) > 0 {
 		r.SetFormDataFromValues(c.FormData)
 	}
+
 	if len(r.FormData) > 0 {
 		handleFormData(r)
 		return
+	} else if len(r.OrderedFormData) > 0 {
+		handleOrderedFormData(r)
+		return
 	}
 
 	// handle marshal body

request.go

@@ -25,20 +25,21 @@ import (
 // req client. Request provides lots of chainable settings which can
 // override client level settings.
 type Request struct {
-	PathParams   map[string]string
-	QueryParams  urlpkg.Values
-	FormData     urlpkg.Values
-	Headers      http.Header
-	Cookies      []*http.Cookie
-	Result       interface{}
-	Error        interface{}
-	RawRequest   *http.Request
-	StartTime    time.Time
-	RetryAttempt int
-	RawURL       string // read only
-	Method       string
-	Body         []byte
-	GetBody      GetContentFunc
+	PathParams      map[string]string
+	QueryParams     urlpkg.Values
+	FormData        urlpkg.Values
+	OrderedFormData []string
+	Headers         http.Header
+	Cookies         []*http.Cookie
+	Result          interface{}
+	Error           interface{}
+	RawRequest      *http.Request
+	StartTime       time.Time
+	RetryAttempt    int
+	RawURL          string // read only
+	Method          string
+	Body            []byte
+	GetBody         GetContentFunc
 	// URL is an auto-generated field, and is nil in request middleware (OnBeforeRequest),
 	// consider using RawURL if you want, it's not nil in client middleware (WrapRoundTripFunc)
 	URL *urlpkg.URL
@@ -187,6 +188,12 @@ func (r *Request) SetFormData(data map[string]string) *Request {
 	return r
 }
 
+// SetOrderedFormData set the ordered form data from key-values pairs.
+func (r *Request) SetOrderedFormData(kvs ...string) *Request {
+	r.OrderedFormData = append(r.OrderedFormData, kvs...)
+	return r
+}
+
 // SetFormDataAnyType set the form data from a map, which value could be any type,
 // will convert to string automatically.
 // It will not been used if request method does not allow payload.