static middleware: do not unescape path twice

The URL path is already unescaped by the http server. Unescaping again
could lead to FileNotFound errors if the file on disk contains '%' chars.

_fixture/special/file with spaces.txt

@@ -0,0 +1 @@
+file with spaces in filename

_fixture/special/file%20with%20percent.txt

@@ -0,0 +1 @@
+file with percents in filename

middleware/static.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"html/template"
 	"net/http"
-	"net/url"
 	"os"
 	"path"
 	"strings"
@@ -171,10 +170,6 @@ func StaticWithConfig(config StaticConfig) echo.MiddlewareFunc {
 			if strings.HasSuffix(c.Path(), "*") { // When serving from a group, e.g. `/static*`.
 				p = c.Param("*")
 			}
-			p, err = url.PathUnescape(p)
-			if err != nil {
-				return
-			}
 			name := path.Join(config.Root, path.Clean("/"+p)) // "/"+ for security
 
 			if config.IgnoreBase {

middleware/static_test.go

@@ -4,6 +4,7 @@ import (
 	"io/fs"
 	"net/http"
 	"net/http/httptest"
+	"net/url"
 	"os"
 	"strings"
 	"testing"
@@ -123,6 +124,30 @@ func TestStatic(t *testing.T) {
 			expectCode:     http.StatusOK,
 			expectContains: "<title>Echo</title>",
 		},
+		{
+			name:           "ok, serve file with whitespace on disk",
+			whenURL:        "/special/" + url.PathEscape("file with spaces.txt"),
+			expectCode:     http.StatusOK,
+			expectContains: "file with spaces in filename",
+		},
+		{
+			name:           "nok, when filename with spaces on disk is decoded twice",
+			whenURL:        "/special/" + url.PathEscape("file%20with%20spaces.txt"),
+			expectCode:     http.StatusNotFound,
+			expectContains: "{\"message\":\"Not Found\"}\n",
+		},
+		{
+			name:           "ok, serve file with '%20' in filename on disk",
+			whenURL:        "/special/" + url.PathEscape("file%20with%20percent.txt"), // file%2520with%2520percent.txt
+			expectCode:     http.StatusOK,
+			expectContains: "file with percents in filename",
+		},
+		{
+			name:           "nok, when filename with '%20' on disk is decoded twice",
+			whenURL:        "/special/file%20with%20percent.txt",
+			expectCode:     http.StatusNotFound,
+			expectContains: "{\"message\":\"Not Found\"}\n",
+		},
 	}
 
 	for _, tc := range testCases {