🔥 v3: update Ctx.Format to match Express's res.format (#2766)

* 🔥 v3: update Ctx.Format to match Express's res.format While the existing Ctx.Format provides a concise convenience method for basic content negotiation on simple structures, res.format allows developers to set their own custom handlers for each content type. The existing Ctx.Format is renamed to Ctx.AutoFormat. * doc: add docs for Ctx.Format * refactor: update based on code review feedback - Rename Fmt to ResFmt - Add comments in several places - Return errors instead of panicking in Format - Add 'Accept' to the Vary header in Format to match res.format * chore: improve docs and tests for AutoFormat and Format
2025-02-06 23:51:40 +00:00 · 2024-01-04 00:50:36 -08:00 · 2024-01-04 00:50:36 -08:00 · 408fa20a91
commit 408fa20a91
parent 2954e3bbae
5 changed files with 328 additions and 36 deletions
--- a/ctx.go
+++ b/ctx.go
@ -105,6 +105,12 @@ type Views interface {
 	Render(io.Writer, string, any, ...string) error
 }

+// ResFmt associates a Content Type to a fiber.Handler for c.Format
+type ResFmt struct {
+	MediaType string
+	Handler   func(Ctx) error
+}
+
 // Accepts checks if the specified extensions or content types are acceptable.
 func (c *DefaultCtx) Accepts(offers ...string) string {
 	return getOffer(c.Get(HeaderAccept), acceptsOfferType, offers...)
@ -375,9 +381,61 @@ func (c *DefaultCtx) Response() *fasthttp.Response {
 }

 // Format performs content-negotiation on the Accept HTTP header.
+// It uses Accepts to select a proper format and calls the matching
+// user-provided handler function.
+// If no accepted format is found, and a format with MediaType "default" is given,
+// that default handler is called. If no format is found and no default is given,
+// StatusNotAcceptable is sent.
+func (c *DefaultCtx) Format(handlers ...ResFmt) error {
+	if len(handlers) == 0 {
+		return ErrNoHandlers
+	}
+
+	c.Vary(HeaderAccept)
+
+	if c.Get(HeaderAccept) == "" {
+		c.Response().Header.SetContentType(handlers[0].MediaType)
+		return handlers[0].Handler(c)
+	}
+
+	// Using an int literal as the slice capacity allows for the slice to be
+	// allocated on the stack. The number was chosen arbitrarily as an
+	// approximation of the maximum number of content types a user might handle.
+	// If the user goes over, it just causes allocations, so it's not a problem.
+	types := make([]string, 0, 8)
+	var defaultHandler Handler
+	for _, h := range handlers {
+		if h.MediaType == "default" {
+			defaultHandler = h.Handler
+			continue
+		}
+		types = append(types, h.MediaType)
+	}
+	accept := c.Accepts(types...)
+
+	if accept == "" {
+		if defaultHandler == nil {
+			return c.SendStatus(StatusNotAcceptable)
+		}
+		return defaultHandler(c)
+	}
+
+	for _, h := range handlers {
+		if h.MediaType == accept {
+			c.Response().Header.SetContentType(h.MediaType)
+			return h.Handler(c)
+		}
+	}
+
+	return fmt.Errorf("%w: format: an Accept was found but no handler was called", errUnreachable)
+}
+
+// AutoFormat performs content-negotiation on the Accept HTTP header.
 // It uses Accepts to select a proper format.
+// The supported content types are text/html, text/plain, application/json, and application/xml.
+// For more flexible content negotiation, use Format.
 // If the header is not specified or there is no proper format, text/plain is used.
-func (c *DefaultCtx) Format(body any) error {
+func (c *DefaultCtx) AutoFormat(body any) error {
 	// Get accepted content type
 	accept := c.Accepts("html", "json", "txt", "xml")
 	// Set accepted content type
--- a/ctx_interface.go
+++ b/ctx_interface.go
@ -90,9 +90,19 @@ type Ctx interface {
 	Response() *fasthttp.Response

 	// Format performs content-negotiation on the Accept HTTP header.
+	// It uses Accepts to select a proper format and calls the matching
+	// user-provided handler function.
+	// If no accepted format is found, and a format with MediaType "default" is given,
+	// that default handler is called. If no format is found and no default is given,
+	// StatusNotAcceptable is sent.
+	Format(handlers ...ResFmt) error
+
+	// AutoFormat performs content-negotiation on the Accept HTTP header.
 	// It uses Accepts to select a proper format.
+	// The supported content types are text/html, text/plain, application/json, and application/xml.
+	// For more flexible content negotiation, use Format.
 	// If the header is not specified or there is no proper format, text/plain is used.
-	Format(body any) error
+	AutoFormat(body any) error

 	// FormFile returns the first file by key from a MultipartForm.
 	FormFile(key string) (*multipart.FileHeader, error)
--- a/ctx_test.go
+++ b/ctx_test.go
@ -717,49 +717,198 @@ func Test_Ctx_Format(t *testing.T) {
 	app := New()
 	c := app.NewCtx(&fasthttp.RequestCtx{})

+	// set `accepted` to whatever media type was chosen by Format
+	var accepted string
+	formatHandlers := func(types ...string) []ResFmt {
+		fmts := []ResFmt{}
+		for _, t := range types {
+			t := utils.CopyString(t)
+			fmts = append(fmts, ResFmt{t, func(c Ctx) error {
+				accepted = t
+				return nil
+			}})
+		}
+		return fmts
+	}
+
+	c.Request().Header.Set(HeaderAccept, `text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7`)
+	err := c.Format(formatHandlers("application/xhtml+xml", "application/xml", "foo/bar")...)
+	require.Equal(t, "application/xhtml+xml", accepted)
+	require.Equal(t, "application/xhtml+xml", c.GetRespHeader(HeaderContentType))
+	require.NoError(t, err)
+	require.NotEqual(t, StatusNotAcceptable, c.Response().StatusCode())
+
+	err = c.Format(formatHandlers("foo/bar;a=b")...)
+	require.Equal(t, "foo/bar;a=b", accepted)
+	require.Equal(t, "foo/bar;a=b", c.GetRespHeader(HeaderContentType))
+	require.NoError(t, err)
+	require.NotEqual(t, StatusNotAcceptable, c.Response().StatusCode())
+
+	myError := errors.New("this is an error")
+	err = c.Format(ResFmt{"text/html", func(c Ctx) error { return myError }})
+	require.ErrorIs(t, err, myError)
+
+	c.Request().Header.Set(HeaderAccept, "application/json")
+	err = c.Format(ResFmt{"text/html", func(c Ctx) error { return c.SendStatus(StatusOK) }})
+	require.Equal(t, StatusNotAcceptable, c.Response().StatusCode())
+	require.NoError(t, err)
+
+	err = c.Format(formatHandlers("text/html", "default")...)
+	require.Equal(t, "default", accepted)
+	require.Equal(t, "text/html", c.GetRespHeader(HeaderContentType))
+	require.NoError(t, err)
+
+	err = c.Format()
+	require.ErrorIs(t, err, ErrNoHandlers)
+}
+
+func Benchmark_Ctx_Format(b *testing.B) {
+	app := New()
+	c := app.NewCtx(&fasthttp.RequestCtx{})
+	c.Request().Header.Set(HeaderAccept, "application/json,text/plain; format=flowed; q=0.9")
+
+	fail := func(_ Ctx) error {
+		require.FailNow(b, "Wrong type chosen")
+		return errors.New("Wrong type chosen")
+	}
+	ok := func(_ Ctx) error {
+		return nil
+	}
+
+	var err error
+	b.Run("with arg allocation", func(b *testing.B) {
+		for n := 0; n < b.N; n++ {
+			err = c.Format(
+				ResFmt{"application/xml", fail},
+				ResFmt{"text/html", fail},
+				ResFmt{"text/plain;format=fixed", fail},
+				ResFmt{"text/plain;format=flowed", ok},
+			)
+		}
+		require.NoError(b, err)
+	})
+
+	b.Run("pre-allocated args", func(b *testing.B) {
+		offers := []ResFmt{
+			{"application/xml", fail},
+			{"text/html", fail},
+			{"text/plain;format=fixed", fail},
+			{"text/plain;format=flowed", ok},
+		}
+		for n := 0; n < b.N; n++ {
+			err = c.Format(offers...)
+		}
+		require.NoError(b, err)
+	})
+
+	c.Request().Header.Set("Accept", "text/plain")
+	b.Run("text/plain", func(b *testing.B) {
+		offers := []ResFmt{
+			{"application/xml", fail},
+			{"text/plain", ok},
+		}
+		for n := 0; n < b.N; n++ {
+			err = c.Format(offers...)
+		}
+		require.NoError(b, err)
+	})
+
+	c.Request().Header.Set("Accept", "json")
+	b.Run("json", func(b *testing.B) {
+		offers := []ResFmt{
+			{"xml", fail},
+			{"html", fail},
+			{"json", ok},
+		}
+		for n := 0; n < b.N; n++ {
+			err = c.Format(offers...)
+		}
+		require.NoError(b, err)
+	})
+}
+
+// go test -run Test_Ctx_AutoFormat
+func Test_Ctx_AutoFormat(t *testing.T) {
+	t.Parallel()
+	app := New()
+	c := app.NewCtx(&fasthttp.RequestCtx{})
+
 	c.Request().Header.Set(HeaderAccept, MIMETextPlain)
-	err := c.Format([]byte("Hello, World!"))
+	err := c.AutoFormat([]byte("Hello, World!"))
 	require.NoError(t, err)
 	require.Equal(t, "Hello, World!", string(c.Response().Body()))

 	c.Request().Header.Set(HeaderAccept, MIMETextHTML)
-	err = c.Format("Hello, World!")
+	err = c.AutoFormat("Hello, World!")
 	require.NoError(t, err)
 	require.Equal(t, "<p>Hello, World!</p>", string(c.Response().Body()))

 	c.Request().Header.Set(HeaderAccept, MIMEApplicationJSON)
-	err = c.Format("Hello, World!")
+	err = c.AutoFormat("Hello, World!")
 	require.NoError(t, err)
 	require.Equal(t, `"Hello, World!"`, string(c.Response().Body()))

 	c.Request().Header.Set(HeaderAccept, MIMETextPlain)
-	err = c.Format(complex(1, 1))
+	err = c.AutoFormat(complex(1, 1))
 	require.NoError(t, err)
 	require.Equal(t, "(1+1i)", string(c.Response().Body()))

 	c.Request().Header.Set(HeaderAccept, MIMEApplicationXML)
-	err = c.Format("Hello, World!")
+	err = c.AutoFormat("Hello, World!")
 	require.NoError(t, err)
 	require.Equal(t, `<string>Hello, World!</string>`, string(c.Response().Body()))

-	err = c.Format(complex(1, 1))
+	err = c.AutoFormat(complex(1, 1))
 	require.Error(t, err)

 	c.Request().Header.Set(HeaderAccept, MIMETextPlain)
-	err = c.Format(Map{})
+	err = c.AutoFormat(Map{})
 	require.NoError(t, err)
 	require.Equal(t, "map[]", string(c.Response().Body()))

 	type broken string
 	c.Request().Header.Set(HeaderAccept, "broken/accept")
 	require.NoError(t, err)
-	err = c.Format(broken("Hello, World!"))
+	err = c.AutoFormat(broken("Hello, World!"))
 	require.NoError(t, err)
 	require.Equal(t, `Hello, World!`, string(c.Response().Body()))
 }

-// go test -v -run=^$ -bench=Benchmark_Ctx_Format -benchmem -count=4
-func Benchmark_Ctx_Format(b *testing.B) {
+func Test_Ctx_AutoFormat_Struct(t *testing.T) {
+	t.Parallel()
+	app := New()
+	c := app.NewCtx(&fasthttp.RequestCtx{})
+
+	type Message struct {
+		Recipients []string
+		Sender     string `xml:"sender,attr"`
+		Urgency    int    `xml:"urgency,attr"`
+	}
+	data := Message{
+		Recipients: []string{"Alice", "Bob"},
+		Sender:     "Carol",
+		Urgency:    3,
+	}
+
+	c.Request().Header.Set(HeaderAccept, MIMEApplicationJSON)
+	err := c.AutoFormat(data)
+	require.NoError(t, err)
+	require.Equal(t,
+		`{"Recipients":["Alice","Bob"],"Sender":"Carol","Urgency":3}`,
+		string(c.Response().Body()),
+	)
+
+	c.Request().Header.Set(HeaderAccept, MIMEApplicationXML)
+	err = c.AutoFormat(data)
+	require.NoError(t, err)
+	require.Equal(t,
+		`<Message sender="Carol" urgency="3"><Recipients>Alice</Recipients><Recipients>Bob</Recipients></Message>`,
+		string(c.Response().Body()),
+	)
+}
+
+// go test -v -run=^$ -bench=Benchmark_Ctx_AutoFormat -benchmem -count=4
+func Benchmark_Ctx_AutoFormat(b *testing.B) {
 	app := New()
 	c := app.NewCtx(&fasthttp.RequestCtx{})

@ -769,14 +918,14 @@ func Benchmark_Ctx_Format(b *testing.B) {

 	var err error
 	for n := 0; n < b.N; n++ {
-		err = c.Format("Hello, World!")
+		err = c.AutoFormat("Hello, World!")
 	}
 	require.NoError(b, err)
 	require.Equal(b, `Hello, World!`, string(c.Response().Body()))
 }

-// go test -v -run=^$ -bench=Benchmark_Ctx_Format_HTML -benchmem -count=4
-func Benchmark_Ctx_Format_HTML(b *testing.B) {
+// go test -v -run=^$ -bench=Benchmark_Ctx_AutoFormat_HTML -benchmem -count=4
+func Benchmark_Ctx_AutoFormat_HTML(b *testing.B) {
 	app := New()
 	c := app.NewCtx(&fasthttp.RequestCtx{})

@ -786,14 +935,14 @@ func Benchmark_Ctx_Format_HTML(b *testing.B) {

 	var err error
 	for n := 0; n < b.N; n++ {
-		err = c.Format("Hello, World!")
+		err = c.AutoFormat("Hello, World!")
 	}
 	require.NoError(b, err)
 	require.Equal(b, "<p>Hello, World!</p>", string(c.Response().Body()))
 }

-// go test -v -run=^$ -bench=Benchmark_Ctx_Format_JSON -benchmem -count=4
-func Benchmark_Ctx_Format_JSON(b *testing.B) {
+// go test -v -run=^$ -bench=Benchmark_Ctx_AutoFormat_JSON -benchmem -count=4
+func Benchmark_Ctx_AutoFormat_JSON(b *testing.B) {
 	app := New()
 	c := app.NewCtx(&fasthttp.RequestCtx{})

@ -803,14 +952,14 @@ func Benchmark_Ctx_Format_JSON(b *testing.B) {

 	var err error
 	for n := 0; n < b.N; n++ {
-		err = c.Format("Hello, World!")
+		err = c.AutoFormat("Hello, World!")
 	}
 	require.NoError(b, err)
 	require.Equal(b, `"Hello, World!"`, string(c.Response().Body()))
 }

-// go test -v -run=^$ -bench=Benchmark_Ctx_Format_XML -benchmem -count=4
-func Benchmark_Ctx_Format_XML(b *testing.B) {
+// go test -v -run=^$ -bench=Benchmark_Ctx_AutoFormat_XML -benchmem -count=4
+func Benchmark_Ctx_AutoFormat_XML(b *testing.B) {
 	app := New()
 	c := app.NewCtx(&fasthttp.RequestCtx{})

@ -820,7 +969,7 @@ func Benchmark_Ctx_Format_XML(b *testing.B) {

 	var err error
 	for n := 0; n < b.N; n++ {
-		err = c.Format("Hello, World!")
+		err = c.AutoFormat("Hello, World!")
 	}
 	require.NoError(b, err)
 	require.Equal(b, `<string>Hello, World!</string>`, string(c.Response().Body()))
--- a/docs/api/ctx.md
+++ b/docs/api/ctx.md
@ -184,6 +184,47 @@ app.Get("/", func(c *fiber.Ctx) error {
 })
 ```

+## AutoFormat
+
+Performs content-negotiation on the [Accept](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept) HTTP header. It uses [Accepts](ctx.md#accepts) to select a proper format.
+The supported content types are `text/html`, `text/plain`, `application/json`, and `application/xml`.
+For more flexible content negotiation, use [Format](ctx.md#format).
+
+
+:::info
+If the header is **not** specified or there is **no** proper format, **text/plain** is used.
+:::
+
+```go title="Signature"
+func (c *Ctx) AutoFormat(body any) error
+```
+
+```go title="Example"
+app.Get("/", func(c fiber.Ctx) error {
+  // Accept: text/plain
+  c.AutoFormat("Hello, World!")
+  // => Hello, World!
+
+  // Accept: text/html
+  c.AutoFormat("Hello, World!")
+  // => <p>Hello, World!</p>
+
+  type User struct {
+    Name string
+  }
+  user := User{"John Doe"}
+
+  // Accept: application/json
+  c.AutoFormat(user)
+  // => {"Name":"John Doe"}
+
+  // Accept: application/xml
+  c.AutoFormat(user)
+  // => <User><Name>John Doe</Name></User>
+  // ..
+})
+```
+
 ## BaseURL

 Returns the base URL \(**protocol** + **host**\) as a `string`.
@ -510,30 +551,54 @@ app.Get("/", func(c *fiber.Ctx) error {

 ## Format

-Performs content-negotiation on the [Accept](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept) HTTP header. It uses [Accepts](ctx.md#accepts) to select a proper format.
+Performs content-negotiation on the [Accept](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept) HTTP header. It uses [Accepts](ctx.md#accepts) to select a proper format from the supplied offers. A default handler can be provided by setting the `MediaType` to `"default"`. If no offers match and no default is provided, a 406 (Not Acceptable) response is sent. The Content-Type is automatically set when a handler is selected.

 :::info
-If the header is **not** specified or there is **no** proper format, **text/plain** is used.
+If the Accept header is **not** specified, the first handler will be used.
 :::

 ```go title="Signature"
-func (c *Ctx) Format(body interface{}) error
+func (c *Ctx) Format(handlers ...ResFmt) error
 ```

 ```go title="Example"
-app.Get("/", func(c *fiber.Ctx) error {
-  // Accept: text/plain
-  c.Format("Hello, World!")
-  // => Hello, World!
+// Accept: application/json => {"command":"eat","subject":"fruit"}
+// Accept: text/plain => Eat Fruit!
+// Accept: application/xml => Not Acceptable
+app.Get("/no-default", func(c fiber.Ctx) error {
+  return c.Format(
+    fiber.ResFmt{"application/json", func(c fiber.Ctx) error {
+      return c.JSON(fiber.Map{
+        "command": "eat",
+        "subject": "fruit",
+      })
+    }},
+    fiber.ResFmt{"text/plain", func(c fiber.Ctx) error {
+      return c.SendString("Eat Fruit!")
+    }},
+  )
+})

-  // Accept: text/html
-  c.Format("Hello, World!")
-  // => <p>Hello, World!</p>
+// Accept: application/json => {"command":"eat","subject":"fruit"}
+// Accept: text/plain => Eat Fruit!
+// Accept: application/xml => Eat Fruit!
+app.Get("/default", func(c fiber.Ctx) error {
+  textHandler := func(c fiber.Ctx) error {
+    return c.SendString("Eat Fruit!")
+  }

-  // Accept: application/json
-  c.Format("Hello, World!")
-  // => "Hello, World!"
-  // ..
+  handlers := []fiber.ResFmt{
+    {"application/json", func(c fiber.Ctx) error {
+      return c.JSON(fiber.Map{
+        "command": "eat",
+        "subject": "fruit",
+      })
+    }},
+    {"text/plain", textHandler},
+    {"default", textHandler},
+  }
+
+  return c.Format(handlers...)
 })
 ```

--- a/error.go
+++ b/error.go
@ -7,6 +7,10 @@ import (
 	"github.com/gofiber/fiber/v3/internal/schema"
 )

+// Wrap and return this for unreachable code if panicking is undesirable (i.e., in a handler).
+// Unexported because users will hopefully never need to see it.
+var errUnreachable = stdErrors.New("fiber: unreachable code, please create an issue at github.com/gofiber/fiber")
+
 // Graceful shutdown errors
 var (
 	ErrGracefulTimeout = stdErrors.New("shutdown: graceful timeout has been reached, exiting")
@ -26,6 +30,12 @@ var (
 // Binder errors
 var ErrCustomBinderNotFound = stdErrors.New("binder: custom binder not found, please be sure to enter the right name")

+// Format errors
+var (
+	// ErrNoHandlers is returned when c.Format is called with no arguments.
+	ErrNoHandlers = stdErrors.New("format: at least one handler is required, but none were set")
+)
+
 // gorilla/schema errors
 type (
 	// ConversionError Conversion error exposes the internal schema.ConversionError for public use.