add io/fs support to static mw

docs/middleware/static.md

@@ -108,6 +108,7 @@ If you want to define static routes using `Get`, you need to use wildcard (`*`)
 | Property   | Type                    | Description                                                                                                                | Default                |
 |:-----------|:------------------------|:---------------------------------------------------------------------------------------------------------------------------|:-----------------------|
 | Next       | `func(fiber.Ctx) bool` | Next defines a function to skip this middleware when returned true.                                                                              | `nil`                  |
+| FS       | `fs.FS` | FS is the file system to serve the static files from.<br /><br />You can use interfaces compatible with fs.FS like embed.FS, os.DirFS etc.                                                 | `nil`                  |
 | Compress       | `bool` | When set to true, the server tries minimizing CPU usage by caching compressed files.<br /><br />This works differently than the github.com/gofiber/compression middleware.                                                                              | `false`                  |
 | ByteRange       | `bool` | When set to true, enables byte range requests.                                                                             | `false`                  |
 | Browse       | `bool` | When set to true, enables directory browsing.                                                                             | `false`                  |

middleware/static/config.go

@@ -15,6 +15,7 @@ type Config struct {
 	Next func(c fiber.Ctx) bool
 
 	// FS is the file system to serve the static files from.
+	// You can use interfaces compatible with fs.FS like embed.FS, os.DirFS etc.
 	//
 	// Optional. Default: nil
 	FS fs.FS

middleware/static/static.go

@@ -1,12 +1,14 @@
 package static
 
 import (
+	"io/fs"
 	"os"
 	"strconv"
 	"strings"
 	"sync"
 
 	"github.com/gofiber/fiber/v3"
+	"github.com/gofiber/utils/v2"
 	"github.com/valyala/fasthttp"
 )
 
@@ -22,14 +24,10 @@ func New(root string, cfg ...Config) fiber.Handler {
 	var cacheControlValue string
 
 	// adjustments for io/fs compatibility
-	if config.FS != nil && root != "" {
+	if config.FS != nil && root == "" {
 		root = "."
 	}
 
-	if root != "." && !strings.HasPrefix(root, "/") {
-		root = "./" + root
-	}
-
 	return func(c fiber.Ctx) error {
 		// Don't execute middleware if Next returns true
 		if config.Next != nil && config.Next(c) {
@@ -77,14 +75,16 @@ func New(root string, cfg ...Config) fiber.Handler {
 				path := fctx.Path()
 
 				if len(path) >= prefixLen {
-					checkFile, err := isFile(root)
+					checkFile, err := isFile(root, fs.FS)
 					if err != nil {
 						return path
 					}
 
 					// If the root is a file, we need to reset the path to "/" always.
-					if checkFile {
+					if checkFile && fs.FS == nil {
 						path = append(path[0:0], '/')
+					} else if checkFile && fs.FS != nil {
+						path = utils.UnsafeBytes(root)
 					} else {
 						path = path[prefixLen:]
 						if len(path) == 0 || path[len(path)-1] != '/' {
@@ -145,10 +145,20 @@ func New(root string, cfg ...Config) fiber.Handler {
 }
 
 // isFile checks if the root is a file.
-func isFile(root string) (bool, error) {
-	file, err := os.Open(root)
-	if err != nil {
-		return false, err
+func isFile(root string, filesystem fs.FS) (bool, error) {
+	var file fs.File
+	var err error
+
+	if filesystem != nil {
+		file, err = filesystem.Open(root)
+		if err != nil {
+			return false, err
+		}
+	} else {
+		file, err = os.Open(root)
+		if err != nil {
+			return false, err
+		}
 	}
 
 	stat, err := file.Stat()

middleware/static/static_test.go

@@ -3,6 +3,7 @@ package static
 import (
 	"embed"
 	"io"
+	"io/fs"
 	"net/http/httptest"
 	"os"
 	"strings"
@@ -527,7 +528,8 @@ func Test_Static_FS_Prefix_Wildcard(t *testing.T) {
 	app := fiber.New()
 
 	app.Get("/test*", New("index.html", Config{
-		FS: os.DirFS("../../.github"),
+		FS:    os.DirFS("../../.github"),
+		Index: "not_index.html",
 	}))
 
 	req := httptest.NewRequest(fiber.MethodGet, "/test/john/doe", nil)
@@ -541,3 +543,75 @@ func Test_Static_FS_Prefix_Wildcard(t *testing.T) {
 	require.NoError(t, err)
 	require.Contains(t, string(body), "Test file")
 }
+
+func Test_isFile(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		name       string
+		path       string
+		filesystem fs.FS
+		expected   bool
+		gotError   error
+	}{
+		{
+			name:       "file",
+			path:       "index.html",
+			filesystem: os.DirFS("../../.github"),
+			expected:   true,
+		},
+		{
+			name:       "file",
+			path:       "index2.html",
+			filesystem: os.DirFS("../../.github"),
+			expected:   false,
+			gotError:   fs.ErrNotExist,
+		},
+		{
+			name:       "directory",
+			path:       ".",
+			filesystem: os.DirFS("../../.github"),
+			expected:   false,
+		},
+		{
+			name:       "directory",
+			path:       "not_exists",
+			filesystem: os.DirFS("../../.github"),
+			expected:   false,
+			gotError:   fs.ErrNotExist,
+		},
+		{
+			name:       "directory",
+			path:       ".",
+			filesystem: os.DirFS("../../.github/testdata/fs/css"),
+			expected:   false,
+		},
+		{
+			name:       "file",
+			path:       "../../.github/testdata/fs/css/style.css",
+			filesystem: nil,
+			expected:   true,
+		},
+		{
+			name:       "file",
+			path:       "../../.github/testdata/fs/css/style2.css",
+			filesystem: nil,
+			expected:   false,
+			gotError:   fs.ErrNotExist,
+		},
+		{
+			name:       "directory",
+			path:       "../../.github/testdata/fs/css",
+			filesystem: nil,
+			expected:   false,
+		},
+	}
+
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			actual, err := isFile(c.path, c.filesystem)
+			require.ErrorIs(t, err, c.gotError)
+			require.Equal(t, c.expected, actual)
+		})
+	}
+}