✨ feature: add XML to context. (#2003)

* ✨ feature: add XML to context.

* Update app.go

app.go

@@ -23,6 +23,7 @@ import (
 	"time"
 
 	"encoding/json"
+	"encoding/xml"
 
 	"github.com/gofiber/fiber/v2/utils"
 	"github.com/valyala/fasthttp"
@@ -324,6 +325,13 @@ type Config struct {
 	// Default: json.Unmarshal
 	JSONDecoder utils.JSONUnmarshal `json:"-"`
 
+	// XMLEncoder set by an external client of Fiber it will use the provided implementation of a
+	// XMLMarshal
+	//
+	// Allowing for flexibility in using another XML library for encoding
+	// Default: xml.Marshal
+	XMLEncoder utils.XMLMarshal `json:"-"`
+
 	// Known networks are "tcp", "tcp4" (IPv4-only), "tcp6" (IPv6-only)
 	// WARNING: When prefork is set to true, only "tcp4" and "tcp6" can be chose.
 	//
@@ -513,6 +521,9 @@ func New(config ...Config) *App {
 	if app.config.JSONDecoder == nil {
 		app.config.JSONDecoder = json.Unmarshal
 	}
+	if app.config.XMLEncoder == nil {
+		app.config.XMLEncoder = xml.Marshal
+	}
 	if app.config.Network == "" {
 		app.config.Network = NetworkTCP4
 	}

ctx.go

@@ -518,12 +518,7 @@ func (c *Ctx) Format(body interface{}) error {
 	case "txt":
 		return c.SendString(b)
 	case "xml":
-		raw, err := xml.Marshal(body)
-		if err != nil {
-			return fmt.Errorf("error serializing xml: %v", body)
-		}
-		c.fasthttp.Response.SetBody(raw)
-		return nil
+		return c.XML(body)
 	}
 	return c.SendString(b)
 }
@@ -736,6 +731,18 @@ func (c *Ctx) JSONP(data interface{}, callback ...string) error {
 	return c.SendString(result)
 }
 
+// XML converts any interface or string to XML.
+// This method also sets the content header to application/xml.
+func (c *Ctx) XML(data interface{}) error {
+	raw, err := c.app.config.XMLEncoder(data)
+	if err != nil {
+		return err
+	}
+	c.fasthttp.Response.SetBodyRaw(raw)
+	c.fasthttp.Response.Header.SetContentType(MIMEApplicationXML)
+	return nil
+}
+
 // Links joins the links followed by the property to populate the response's Link HTTP header field.
 func (c *Ctx) Links(link ...string) {
 	if len(link) == 0 {

ctx_test.go

@@ -12,6 +12,7 @@ import (
 	"bytes"
 	"compress/gzip"
 	"context"
+	"encoding/xml"
 	"errors"
 	"fmt"
 	"io"
@@ -2134,6 +2135,65 @@ func Benchmark_Ctx_JSONP(b *testing.B) {
 	utils.AssertEqual(b, `emit({"Name":"Grame","Age":20});`, string(c.Response().Body()))
 }
 
+// go test -run Test_Ctx_XML
+func Test_Ctx_XML(t *testing.T) {
+	t.Parallel()
+	app := New()
+	c := app.AcquireCtx(&fasthttp.RequestCtx{})
+	defer app.ReleaseCtx(c)
+
+	utils.AssertEqual(t, true, c.JSON(complex(1, 1)) != nil)
+
+	type xmlResult struct {
+		XMLName xml.Name `xml:"Users"`
+		Names   []string `xml:"Names"`
+		Ages    []int    `xml:"Ages"`
+	}
+
+	c.XML(xmlResult{
+		Names: []string{"Grame", "John"},
+		Ages:  []int{1, 12, 20},
+	})
+
+	utils.AssertEqual(t, `<Users><Names>Grame</Names><Names>John</Names><Ages>1</Ages><Ages>12</Ages><Ages>20</Ages></Users>`, string(c.Response().Body()))
+	utils.AssertEqual(t, "application/xml", string(c.Response().Header.Peek("content-type")))
+
+	testEmpty := func(v interface{}, r string) {
+		err := c.XML(v)
+		utils.AssertEqual(t, nil, err)
+		utils.AssertEqual(t, r, string(c.Response().Body()))
+	}
+
+	testEmpty(nil, "")
+	testEmpty("", `<string></string>`)
+	testEmpty(0, "<int>0</int>")
+	testEmpty([]int{}, "")
+}
+
+// go test -run=^$ -bench=Benchmark_Ctx_XML -benchmem -count=4
+func Benchmark_Ctx_XML(b *testing.B) {
+	app := New()
+	c := app.AcquireCtx(&fasthttp.RequestCtx{})
+	defer app.ReleaseCtx(c)
+	type SomeStruct struct {
+		Name string `xml:"Name"`
+		Age  uint8  `xml:"Age"`
+	}
+	data := SomeStruct{
+		Name: "Grame",
+		Age:  20,
+	}
+	var err error
+	b.ReportAllocs()
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		err = c.XML(data)
+	}
+
+	utils.AssertEqual(b, nil, err)
+	utils.AssertEqual(b, `<SomeStruct><Name>Grame</Name><Age>20</Age></SomeStruct>`, string(c.Response().Body()))
+}
+
 // go test -run Test_Ctx_Links
 func Test_Ctx_Links(t *testing.T) {
 	t.Parallel()

utils/xml.go

@@ -0,0 +1,4 @@
+package utils
+
+// XMLMarshal returns the XML encoding of v.
+type XMLMarshal func(v interface{}) ([]byte, error)

utils/xml_test.go

@@ -0,0 +1,59 @@
+package utils
+
+import (
+	"encoding/xml"
+	"testing"
+)
+
+type serversXMLStructure struct {
+	XMLName xml.Name             `xml:"servers"`
+	Version string               `xml:"version,attr"`
+	Servers []serverXMLStructure `xml:"server"`
+}
+
+type serverXMLStructure struct {
+	XMLName xml.Name `xml:"server"`
+	Name    string   `xml:"name"`
+}
+
+var xmlString = `<servers version="1"><server><name>fiber one</name></server><server><name>fiber two</name></server></servers>`
+
+func Test_GolangXMLEncoder(t *testing.T) {
+	t.Parallel()
+
+	var (
+		ss = &serversXMLStructure{
+			Version: "1",
+			Servers: []serverXMLStructure{
+				{Name: "fiber one"},
+				{Name: "fiber two"},
+			},
+		}
+		xmlEncoder XMLMarshal = xml.Marshal
+	)
+
+	raw, err := xmlEncoder(ss)
+	AssertEqual(t, err, nil)
+
+	AssertEqual(t, string(raw), xmlString)
+}
+
+func Test_DefaultXMLEncoder(t *testing.T) {
+	t.Parallel()
+
+	var (
+		ss = &serversXMLStructure{
+			Version: "1",
+			Servers: []serverXMLStructure{
+				{Name: "fiber one"},
+				{Name: "fiber two"},
+			},
+		}
+		xmlEncoder XMLMarshal = xml.Marshal
+	)
+
+	raw, err := xmlEncoder(ss)
+	AssertEqual(t, err, nil)
+
+	AssertEqual(t, string(raw), xmlString)
+}