📚 Doc: Clarify SendFile Docs (#3172)

* 📚 Doc: Clarify SendFile ContentType header set by file format

* 📚 Doc: Make SendFile default value formatting consistent

* 📚 Doc: Add missing `fiber.` in SendFile usage docs

* 📚 Doc: Hyphenate 'case-sensitive'

* 📚 Doc: Clarify `SendFile` behavior for missing/invalid file extensions

* 🚨 Test: Validate `SendFile` Content-Type header

---------

Co-authored-by: Juan Calderon-Perez <[email protected]>

app.go

@@ -142,7 +142,7 @@ type Config struct { //nolint:govet // Aligning the struct fields is not necessa
 	// Default: false
 	StrictRouting bool `json:"strict_routing"`
 
-	// When set to true, enables case sensitive routing.
+	// When set to true, enables case-sensitive routing.
 	// E.g. "/FoO" and "/foo" are treated as different routes.
 	// By default this is disabled and both "/FoO" and "/foo" will execute the same handler.
 	//

app_test.go

@@ -451,9 +451,9 @@ func Test_App_Use_CaseSensitive(t *testing.T) {
 	require.NoError(t, err, "app.Test(req)")
 	require.Equal(t, StatusOK, resp.StatusCode, "Status code")
 
-	// check the detected path when the case insensitive recognition is activated
+	// check the detected path when the case-insensitive recognition is activated
 	app.config.CaseSensitive = false
-	// check the case sensitive feature
+	// check the case-sensitive feature
 	resp, err = app.Test(httptest.NewRequest(MethodGet, "/AbC", nil))
 	require.NoError(t, err, "app.Test(req)")
 	require.Equal(t, StatusOK, resp.StatusCode, "Status code")

ctx.go

@@ -83,29 +83,29 @@ type SendFile struct {
 	// You have to set Content-Encoding header to compress the file.
 	// Available compression methods are gzip, br, and zstd.
 	//
-	// Optional. Default value false
+	// Optional. Default: false
 	Compress bool `json:"compress"`
 
 	// When set to true, enables byte range requests.
 	//
-	// Optional. Default value false
+	// Optional. Default: false
 	ByteRange bool `json:"byte_range"`
 
 	// When set to true, enables direct download.
 	//
-	// Optional. Default: false.
+	// Optional. Default: false
 	Download bool `json:"download"`
 
 	// Expiration duration for inactive file handlers.
 	// Use a negative time.Duration to disable it.
 	//
-	// Optional. Default value 10 * time.Second.
+	// Optional. Default: 10 * time.Second
 	CacheDuration time.Duration `json:"cache_duration"`
 
 	// The value for the Cache-Control HTTP-header
 	// that is set on the file response. MaxAge is defined in seconds.
 	//
-	// Optional. Default value 0.
+	// Optional. Default: 0
 	MaxAge int `json:"max_age"`
 }
 
@@ -1496,9 +1496,10 @@ func (c *DefaultCtx) Send(body []byte) error {
 	return nil
 }
 
-// SendFile transfers the file from the given path.
-// The file is not compressed by default, enable this by passing a 'true' argument
-// Sets the Content-Type response HTTP header field based on the filenames extension.
+// SendFile transfers the file from the specified path.
+// By default, the file is not compressed. To enable compression, set SendFile.Compress to true.
+// The Content-Type response HTTP header field is set based on the file's extension.
+// If the file extension is missing or invalid, the Content-Type is detected from the file's format.
 func (c *DefaultCtx) SendFile(file string, config ...SendFile) error {
 	// Save the filename, we will need it in the error message if the file isn't found
 	filename := file

ctx_test.go

@@ -3122,6 +3122,49 @@ func Test_Ctx_SendFile(t *testing.T) {
 	app.ReleaseCtx(c)
 }
 
+// go test -race -run Test_Ctx_SendFile_ContentType
+func Test_Ctx_SendFile_ContentType(t *testing.T) {
+	t.Parallel()
+	app := New()
+
+	// 1) simple case
+	c := app.AcquireCtx(&fasthttp.RequestCtx{})
+	err := c.SendFile("./.github/testdata/fs/img/fiber.png")
+	// check expectation
+	require.NoError(t, err)
+	require.Equal(t, StatusOK, c.Response().StatusCode())
+	require.Equal(t, "image/png", string(c.Response().Header.Peek(HeaderContentType)))
+	app.ReleaseCtx(c)
+
+	// 2) set by valid file extension, not file header
+	// see: https://github.com/valyala/fasthttp/blob/d795f13985f16622a949ea9fc3459cf54dc78b3e/fs.go#L1638
+	c = app.AcquireCtx(&fasthttp.RequestCtx{})
+	err = c.SendFile("./.github/testdata/fs/img/fiberpng.jpeg")
+	// check expectation
+	require.NoError(t, err)
+	require.Equal(t, StatusOK, c.Response().StatusCode())
+	require.Equal(t, "image/jpeg", string(c.Response().Header.Peek(HeaderContentType)))
+	app.ReleaseCtx(c)
+
+	// 3) set by file header if extension is invalid
+	c = app.AcquireCtx(&fasthttp.RequestCtx{})
+	err = c.SendFile("./.github/testdata/fs/img/fiberpng.notvalidext")
+	// check expectation
+	require.NoError(t, err)
+	require.Equal(t, StatusOK, c.Response().StatusCode())
+	require.Equal(t, "image/png", string(c.Response().Header.Peek(HeaderContentType)))
+	app.ReleaseCtx(c)
+
+	// 4) set by file header if extension is missing
+	c = app.AcquireCtx(&fasthttp.RequestCtx{})
+	err = c.SendFile("./.github/testdata/fs/img/fiberpng")
+	// check expectation
+	require.NoError(t, err)
+	require.Equal(t, StatusOK, c.Response().StatusCode())
+	require.Equal(t, "image/png", string(c.Response().Header.Peek(HeaderContentType)))
+	app.ReleaseCtx(c)
+}
+
 func Test_Ctx_SendFile_Download(t *testing.T) {
 	t.Parallel()
 	app := New()

docs/api/ctx.md

@@ -1709,7 +1709,7 @@ app.Get("/", func(c fiber.Ctx) error {
 
 ## SendFile
 
-Transfers the file from the given path. Sets the [Content-Type](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Type) response HTTP header field based on the **filenames** extension.
+Transfers the file from the given path. Sets the [Content-Type](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Type) response HTTP header field based on the **file** extension or format.
 
 ```go title="Config" title="Config"
 // SendFile defines configuration options when to transfer file with SendFile.
@@ -1725,29 +1725,29 @@ type SendFile struct {
   // You have to set Content-Encoding header to compress the file.
   // Available compression methods are gzip, br, and zstd.
   //
-  // Optional. Default value false
+  // Optional. Default: false
   Compress bool `json:"compress"`
 
   // When set to true, enables byte range requests.
   //
-  // Optional. Default value false
+  // Optional. Default: false
   ByteRange bool `json:"byte_range"`
 
   // When set to true, enables direct download.
   //
-  // Optional. Default: false.
+  // Optional. Default: false
   Download bool `json:"download"`
 
   // Expiration duration for inactive file handlers.
   // Use a negative time.Duration to disable it.
   //
-  // Optional. Default value 10 * time.Second.
+  // Optional. Default: 10 * time.Second
   CacheDuration time.Duration `json:"cache_duration"`
 
   // The value for the Cache-Control HTTP-header
   // that is set on the file response. MaxAge is defined in seconds.
   //
-    // Optional. Default value 0.
+  // Optional. Default: 0
   MaxAge int `json:"max_age"`
 }
 ```
@@ -1761,7 +1761,7 @@ app.Get("/not-found", func(c fiber.Ctx) error {
   return c.SendFile("./public/404.html");
 
   // Disable compression
-  return c.SendFile("./static/index.html", SendFile{
+  return c.SendFile("./static/index.html", fiber.SendFile{
     Compress: false,
   });
 })
@@ -1783,7 +1783,7 @@ You can set `CacheDuration` config property to `-1` to disable caching.
 
 ```go title="Example"
 app.Get("/file", func(c fiber.Ctx) error {
-  return c.SendFile("style.css", SendFile{
+  return c.SendFile("style.css", fiber.SendFile{
     CacheDuration: -1,
   })
 })
@@ -1797,16 +1797,16 @@ You can use multiple SendFile with different configurations in single route. Fib
 app.Get("/file", func(c fiber.Ctx) error {
   switch c.Query("config") {
     case "filesystem":
-      return c.SendFile("style.css", SendFile{
+      return c.SendFile("style.css", fiber.SendFile{
         FS: os.DirFS(".")
       })
     case "filesystem-compress":
-      return c.SendFile("style.css", SendFile{
+      return c.SendFile("style.css", fiber.SendFile{
         FS: os.DirFS("."),
         Compress: true,
       })
     case "compress":
-      return c.SendFile("style.css", SendFile{
+      return c.SendFile("style.css", fiber.SendFile{
         Compress: true,
       })
     default:

router.go

@@ -52,7 +52,7 @@ type Route struct {
 	Name   string `json:"name"`   // Route's name
 	//nolint:revive // Having both a Path (uppercase) and a path (lowercase) is fine
 	Path        string      `json:"path"`   // Original registered route path
-	Params      []string    `json:"params"` // Case sensitive param keys
+	Params      []string    `json:"params"` // Case-sensitive param keys
 	Handlers    []Handler   `json:"-"`      // Ctx handlers
 	routeParser routeParser // Parameter parser
 	// Data for routing
@@ -316,7 +316,7 @@ func (app *App) register(methods []string, pathRaw string, group *Group, handler
 		if pathRaw[0] != '/' {
 			pathRaw = "/" + pathRaw
 		}
-		// Create a stripped path in-case sensitive / trailing slashes
+		// Create a stripped path in case-sensitive / trailing slashes
 		pathPretty := pathRaw
 		// Case-sensitive routing, all to lowercase
 		if !app.config.CaseSensitive {