🐛 bug: Fix square bracket notation in Multipart FormData (#3235)

* 🐛 bug: add square bracket notation support to BindMultipart

* Fix golangci-lint issues

* Fixing undef variable

* Fix more lint issues

* test

* update1

* improve coverage

* fix linter

* reduce code duplication

* reduce code duplications in bindMultipart

---------

Co-authored-by: Juan Calderon-Perez <835733+gaby@users.noreply.github.com>
Co-authored-by: René <rene@gofiber.io>

bind_test.go

@@ -7,6 +7,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"mime/multipart"
 	"net/http/httptest"
 	"reflect"
 	"testing"
@@ -887,6 +888,7 @@ func Test_Bind_Body(t *testing.T) {
 
 	type Demo struct {
 		Name  string   `json:"name" xml:"name" form:"name" query:"name"`
+		Names []string `json:"names" xml:"names" form:"names" query:"names"`
 	}
 
 	// Helper function to test compressed bodies
@@ -996,6 +998,48 @@ func Test_Bind_Body(t *testing.T) {
 		Data []Demo `query:"data"`
 	}
 
+	t.Run("MultipartCollectionQueryDotNotation", func(t *testing.T) {
+		c := app.AcquireCtx(&fasthttp.RequestCtx{})
+		c.Request().Reset()
+
+		buf := &bytes.Buffer{}
+		writer := multipart.NewWriter(buf)
+		require.NoError(t, writer.WriteField("data.0.name", "john"))
+		require.NoError(t, writer.WriteField("data.1.name", "doe"))
+		require.NoError(t, writer.Close())
+
+		c.Request().Header.SetContentType(writer.FormDataContentType())
+		c.Request().SetBody(buf.Bytes())
+		c.Request().Header.SetContentLength(len(c.Body()))
+
+		cq := new(CollectionQuery)
+		require.NoError(t, c.Bind().Body(cq))
+		require.Len(t, cq.Data, 2)
+		require.Equal(t, "john", cq.Data[0].Name)
+		require.Equal(t, "doe", cq.Data[1].Name)
+	})
+
+	t.Run("MultipartCollectionQuerySquareBrackets", func(t *testing.T) {
+		c := app.AcquireCtx(&fasthttp.RequestCtx{})
+		c.Request().Reset()
+
+		buf := &bytes.Buffer{}
+		writer := multipart.NewWriter(buf)
+		require.NoError(t, writer.WriteField("data[0][name]", "john"))
+		require.NoError(t, writer.WriteField("data[1][name]", "doe"))
+		require.NoError(t, writer.Close())
+
+		c.Request().Header.SetContentType(writer.FormDataContentType())
+		c.Request().SetBody(buf.Bytes())
+		c.Request().Header.SetContentLength(len(c.Body()))
+
+		cq := new(CollectionQuery)
+		require.NoError(t, c.Bind().Body(cq))
+		require.Len(t, cq.Data, 2)
+		require.Equal(t, "john", cq.Data[0].Name)
+		require.Equal(t, "doe", cq.Data[1].Name)
+	})
+
 	t.Run("CollectionQuerySquareBrackets", func(t *testing.T) {
 		c := app.AcquireCtx(&fasthttp.RequestCtx{})
 		c.Request().Reset()
@@ -1192,9 +1236,14 @@ func Benchmark_Bind_Body_MultipartForm(b *testing.B) {
 		Name string `form:"name"`
 	}
 
-	body := []byte("--b\r\nContent-Disposition: form-data; name=\"name\"\r\n\r\njohn\r\n--b--")
+	buf := &bytes.Buffer{}
+	writer := multipart.NewWriter(buf)
+	require.NoError(b, writer.WriteField("name", "john"))
+	require.NoError(b, writer.Close())
+	body := buf.Bytes()
+
 	c.Request().SetBody(body)
-	c.Request().Header.SetContentType(MIMEMultipartForm + `;boundary="b"`)
+	c.Request().Header.SetContentType(MIMEMultipartForm + `;boundary=` + writer.Boundary())
 	c.Request().Header.SetContentLength(len(body))
 	d := new(Demo)
 
@@ -1204,10 +1253,58 @@ func Benchmark_Bind_Body_MultipartForm(b *testing.B) {
 	for n := 0; n < b.N; n++ {
 		err = c.Bind().Body(d)
 	}
+
 	require.NoError(b, err)
 	require.Equal(b, "john", d.Name)
 }
 
+// go test -v -run=^$ -bench=Benchmark_Bind_Body_MultipartForm_Nested -benchmem -count=4
+func Benchmark_Bind_Body_MultipartForm_Nested(b *testing.B) {
+	var err error
+
+	app := New()
+	c := app.AcquireCtx(&fasthttp.RequestCtx{})
+
+	type Person struct {
+		Name string `form:"name"`
+		Age  int    `form:"age"`
+	}
+
+	type Demo struct {
+		Name    string   `form:"name"`
+		Persons []Person `form:"persons"`
+	}
+
+	buf := &bytes.Buffer{}
+	writer := multipart.NewWriter(buf)
+	require.NoError(b, writer.WriteField("name", "john"))
+	require.NoError(b, writer.WriteField("persons.0.name", "john"))
+	require.NoError(b, writer.WriteField("persons[0][age]", "10"))
+	require.NoError(b, writer.WriteField("persons[1][name]", "doe"))
+	require.NoError(b, writer.WriteField("persons.1.age", "20"))
+	require.NoError(b, writer.Close())
+	body := buf.Bytes()
+
+	c.Request().SetBody(body)
+	c.Request().Header.SetContentType(MIMEMultipartForm + `;boundary=` + writer.Boundary())
+	c.Request().Header.SetContentLength(len(body))
+	d := new(Demo)
+
+	b.ReportAllocs()
+	b.ResetTimer()
+
+	for n := 0; n < b.N; n++ {
+		err = c.Bind().Body(d)
+	}
+
+	require.NoError(b, err)
+	require.Equal(b, "john", d.Name)
+	require.Equal(b, "john", d.Persons[0].Name)
+	require.Equal(b, 10, d.Persons[0].Age)
+	require.Equal(b, "doe", d.Persons[1].Name)
+	require.Equal(b, 20, d.Persons[1].Age)
+}
+
 // go test -v -run=^$ -bench=Benchmark_Bind_Body_Form_Map -benchmem -count=4
 func Benchmark_Bind_Body_Form_Map(b *testing.B) {
 	var err error

binder/cookie.go

@@ -1,9 +1,6 @@
 package binder
 
 import (
-	"reflect"
-	"strings"
-
 	"github.com/gofiber/utils/v2"
 	"github.com/valyala/fasthttp"
 )
@@ -30,15 +27,7 @@ func (b *CookieBinding) Bind(req *fasthttp.Request, out any) error {
 
 		k := utils.UnsafeString(key)
 		v := utils.UnsafeString(val)
-
+		err = formatBindData(out, data, k, v, b.EnableSplitting, false)
-		if b.EnableSplitting && strings.Contains(v, ",") && equalFieldType(out, reflect.Slice, k) {
-			values := strings.Split(v, ",")
-			for i := 0; i < len(values); i++ {
-				data[k] = append(data[k], values[i])
-			}
-		} else {
-			data[k] = append(data[k], v)
-		}
 	})
 
 	if err != nil {

binder/form.go

@@ -1,9 +1,6 @@
 package binder
 
 import (
-	"reflect"
-	"strings"
-
 	"github.com/gofiber/utils/v2"
 	"github.com/valyala/fasthttp"
 )
@@ -37,19 +34,7 @@ func (b *FormBinding) Bind(req *fasthttp.Request, out any) error {
 
 		k := utils.UnsafeString(key)
 		v := utils.UnsafeString(val)
-
+		err = formatBindData(out, data, k, v, b.EnableSplitting, true)
-		if strings.Contains(k, "[") {
-			k, err = parseParamSquareBrackets(k)
-		}
-
-		if b.EnableSplitting && strings.Contains(v, ",") && equalFieldType(out, reflect.Slice, k) {
-			values := strings.Split(v, ",")
-			for i := 0; i < len(values); i++ {
-				data[k] = append(data[k], values[i])
-			}
-		} else {
-			data[k] = append(data[k], v)
-		}
 	})
 
 	if err != nil {
@@ -61,12 +46,20 @@ func (b *FormBinding) Bind(req *fasthttp.Request, out any) error {
 
 // bindMultipart parses the request body and returns the result.
 func (b *FormBinding) bindMultipart(req *fasthttp.Request, out any) error {
-	data, err := req.MultipartForm()
+	multipartForm, err := req.MultipartForm()
 	if err != nil {
 		return err
 	}
 
-	return parse(b.Name(), out, data.Value)
+	data := make(map[string][]string)
+	for key, values := range multipartForm.Value {
+		err = formatBindData(out, data, key, values, b.EnableSplitting, true)
+		if err != nil {
+			return err
+		}
+	}
+
+	return parse(b.Name(), out, data)
 }
 
 // Reset resets the FormBinding binder.

binder/form_test.go

@@ -93,9 +93,14 @@ func Test_FormBinder_BindMultipart(t *testing.T) {
 	}
 	require.Equal(t, "form", b.Name())
 
+	type Post struct {
+		Title string `form:"title"`
+	}
+
 	type User struct {
 		Name  string   `form:"name"`
 		Names []string `form:"names"`
+		Posts []Post   `form:"posts"`
 		Age   int      `form:"age"`
 	}
 	var user User
@@ -106,9 +111,13 @@ func Test_FormBinder_BindMultipart(t *testing.T) {
 	mw := multipart.NewWriter(buf)
 
 	require.NoError(t, mw.WriteField("name", "john"))
-	require.NoError(t, mw.WriteField("names", "john"))
+	require.NoError(t, mw.WriteField("names", "john,eric"))
 	require.NoError(t, mw.WriteField("names", "doe"))
 	require.NoError(t, mw.WriteField("age", "42"))
+	require.NoError(t, mw.WriteField("posts[0][title]", "post1"))
+	require.NoError(t, mw.WriteField("posts[1][title]", "post2"))
+	require.NoError(t, mw.WriteField("posts[2][title]", "post3"))
+
 	require.NoError(t, mw.Close())
 
 	req.Header.SetContentType(mw.FormDataContentType())
@@ -125,6 +134,11 @@ func Test_FormBinder_BindMultipart(t *testing.T) {
 	require.Equal(t, 42, user.Age)
 	require.Contains(t, user.Names, "john")
 	require.Contains(t, user.Names, "doe")
+	require.Contains(t, user.Names, "eric")
+	require.Len(t, user.Posts, 3)
+	require.Equal(t, "post1", user.Posts[0].Title)
+	require.Equal(t, "post2", user.Posts[1].Title)
+	require.Equal(t, "post3", user.Posts[2].Title)
 }
 
 func Benchmark_FormBinder_BindMultipart(b *testing.B) {

binder/header.go

@@ -1,9 +1,6 @@
 package binder
 
 import (
-	"reflect"
-	"strings"
-
 	"github.com/gofiber/utils/v2"
 	"github.com/valyala/fasthttp"
 )
@@ -21,20 +18,21 @@ func (*HeaderBinding) Name() string {
 // Bind parses the request header and returns the result.
 func (b *HeaderBinding) Bind(req *fasthttp.Request, out any) error {
 	data := make(map[string][]string)
+	var err error
 	req.Header.VisitAll(func(key, val []byte) {
+		if err != nil {
+			return
+		}
+
 		k := utils.UnsafeString(key)
 		v := utils.UnsafeString(val)
-
+		err = formatBindData(out, data, k, v, b.EnableSplitting, false)
-		if b.EnableSplitting && strings.Contains(v, ",") && equalFieldType(out, reflect.Slice, k) {
-			values := strings.Split(v, ",")
-			for i := 0; i < len(values); i++ {
-				data[k] = append(data[k], values[i])
-			}
-		} else {
-			data[k] = append(data[k], v)
-		}
 	})
 
+	if err != nil {
+		return err
+	}
+
 	return parse(b.Name(), out, data)
 }
 

binder/mapping.go

@@ -107,7 +107,7 @@ func parseToStruct(aliasTag string, out any, data map[string][]string) error {
 func parseToMap(ptr any, data map[string][]string) error {
 	elem := reflect.TypeOf(ptr).Elem()
 
-	switch elem.Kind() { //nolint:exhaustive // it's not necessary to check all types
+	switch elem.Kind() {
 	case reflect.Slice:
 		newMap, ok := ptr.(map[string][]string)
 		if !ok {
@@ -130,6 +130,8 @@ func parseToMap(ptr any, data map[string][]string) error {
 			}
 			newMap[k] = v[len(v)-1]
 		}
+	default:
+		return nil // it's not necessary to check all types
 	}
 
 	return nil
@@ -247,3 +249,37 @@ func FilterFlags(content string) string {
 	}
 	return content
 }
+
+func formatBindData[T any](out any, data map[string][]string, key string, value T, enableSplitting, supportBracketNotation bool) error { //nolint:revive // it's okay
+	var err error
+	if supportBracketNotation && strings.Contains(key, "[") {
+		key, err = parseParamSquareBrackets(key)
+		if err != nil {
+			return err
+		}
+	}
+
+	switch v := any(value).(type) {
+	case string:
+		assignBindData(out, data, key, v, enableSplitting)
+	case []string:
+		for _, val := range v {
+			assignBindData(out, data, key, val, enableSplitting)
+		}
+	default:
+		return fmt.Errorf("unsupported value type: %T", value)
+	}
+
+	return err
+}
+
+func assignBindData(out any, data map[string][]string, key, value string, enableSplitting bool) { //nolint:revive // it's okay
+	if enableSplitting && strings.Contains(value, ",") && equalFieldType(out, reflect.Slice, key) {
+		values := strings.Split(value, ",")
+		for i := 0; i < len(values); i++ {
+			data[key] = append(data[key], values[i])
+		}
+	} else {
+		data[key] = append(data[key], value)
+	}
+}

binder/query.go

@@ -1,9 +1,6 @@
 package binder
 
 import (
-	"reflect"
-	"strings"
-
 	"github.com/gofiber/utils/v2"
 	"github.com/valyala/fasthttp"
 )
@@ -30,19 +27,7 @@ func (b *QueryBinding) Bind(reqCtx *fasthttp.Request, out any) error {
 
 		k := utils.UnsafeString(key)
 		v := utils.UnsafeString(val)
-
+		err = formatBindData(out, data, k, v, b.EnableSplitting, true)
-		if strings.Contains(k, "[") {
-			k, err = parseParamSquareBrackets(k)
-		}
-
-		if b.EnableSplitting && strings.Contains(v, ",") && equalFieldType(out, reflect.Slice, k) {
-			values := strings.Split(v, ",")
-			for i := 0; i < len(values); i++ {
-				data[k] = append(data[k], values[i])
-			}
-		} else {
-			data[k] = append(data[k], v)
-		}
 	})
 
 	if err != nil {

binder/resp_header.go

@@ -1,9 +1,6 @@
 package binder
 
 import (
-	"reflect"
-	"strings"
-
 	"github.com/gofiber/utils/v2"
 	"github.com/valyala/fasthttp"
 )
@@ -21,20 +18,22 @@ func (*RespHeaderBinding) Name() string {
 // Bind parses the response header and returns the result.
 func (b *RespHeaderBinding) Bind(resp *fasthttp.Response, out any) error {
 	data := make(map[string][]string)
+	var err error
+
 	resp.Header.VisitAll(func(key, val []byte) {
+		if err != nil {
+			return
+		}
+
 		k := utils.UnsafeString(key)
 		v := utils.UnsafeString(val)
-
+		err = formatBindData(out, data, k, v, b.EnableSplitting, false)
-		if b.EnableSplitting && strings.Contains(v, ",") && equalFieldType(out, reflect.Slice, k) {
-			values := strings.Split(v, ",")
-			for i := 0; i < len(values); i++ {
-				data[k] = append(data[k], values[i])
-			}
-		} else {
-			data[k] = append(data[k], v)
-		}
 	})
 
+	if err != nil {
+		return err
+	}
+
 	return parse(b.Name(), out, data)
 }