🔥 feat: Add support for NewErrorf

app.go

@@ -881,16 +881,29 @@
 	return e.Message
 }
 
-// NewError creates a new Error instance with an optional message
-func NewError(code int, message ...string) *Error {
-	err := &Error{
-		Code:    code,
-		Message: utils.StatusMessage(code),
-	}
-	if len(message) > 0 {
-		err.Message = message[0]
+// NewError creates a new Error instance with an optional message.
+// Additional arguments are formatted using fmt.Sprintf when provided.
+// If the first argument in the message slice is not a string, the function
+// falls back to using fmt.Sprint on the first element to generate the message.
+func NewError(code int, message ...any) *Error {
+	switch len(message) {
+	case 0:
+		// nothing to override
+	case 1:
+		// One argument → treat it like fmt.Sprint(arg)
+		msg = fmt.Sprint(message[0])
+	default:
+		// Two or more → first must be a format string.
+		if format, ok := message[0].(string); ok {
+			msg = fmt.Sprintf(format, message[1:]...)
+		} else {
+			// If the first arg isn’t a string, fall back gracefully
+			// instead of panicking on the type assertion.
+			msg = fmt.Sprint(message[0])
+		}
 	}
-	return err
+
+	return &Error{Code: code, Message: utils.StatusMessage(code)}
 }
 
 // Config returns the app config as value ( read-only ).

app_test.go

@@ -1309,6 +1309,72 @@ func Test_NewError(t *testing.T) {
 	require.Equal(t, "permission denied", e.Message)
 }
 
+// go test -run Test_NewError_Format
+func Test_NewError_Format(t *testing.T) {
+	t.Parallel()
+
+	type args []any
+
+	tests := []struct { //nolint:govet // fieldalignment: this struct is already optimally ordered
+		name string
+		want string
+		code int
+		in   args
+	}{
+		{
+			name: "no-args → default text",
+			code: StatusNotFound,
+			in:   nil,
+			want: utils.StatusMessage(StatusNotFound),
+		},
+		{
+			name: "single-string arg overrides",
+			code: StatusBadRequest,
+			in:   args{"custom bad request"},
+			want: "custom bad request",
+		},
+		{
+			name: "single non-string arg stringified",
+			code: StatusInternalServerError,
+			in:   args{errors.New("db down")},
+			want: "db down",
+		},
+		{
+			name: "single nil interface",
+			code: StatusInternalServerError,
+			in:   args{any(nil)},
+			want: "<nil>",
+		},
+		{
+			name: "format string + args",
+			code: StatusBadRequest,
+			in:   args{"invalid id %d", 10},
+			want: "invalid id 10",
+		},
+		{
+			name: "format string + excess args",
+			code: StatusBadRequest,
+			in:   args{"odd %d", 1, 2, 3},
+			want: "odd 1%!(EXTRA int=2, int=3)",
+		},
+		{
+			name: "≥2 args but first not string",
+			code: StatusBadRequest,
+			in:   args{errors.New("boom"), 42},
+			want: "boom",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			e := NewError(tt.code, tt.in...)
+			require.Equal(t, tt.code, e.Code)
+			require.Equal(t, tt.want, e.Message)
+		})
+	}
+}
+
 // go test -run Test_Test_Timeout
 func Test_Test_Timeout(t *testing.T) {
 	t.Parallel()

ctx.go

@@ -1652,7 +1652,7 @@ func (c *DefaultCtx) SendFile(file string, config ...SendFile) error {
 
 	// Check for error
 	if status != StatusNotFound && fsStatus == StatusNotFound {
-		return NewError(StatusNotFound, fmt.Sprintf("sendfile: file %s not found", filename))
+		return NewError(StatusNotFound, "sendfile: file %s not found", filename)
 	}
 
 	// Set the status code set by the user if it is different from the fasthttp status code and 200

docs/api/fiber.md

@@ -243,12 +243,12 @@ func (app *App) ShutdownWithContext(ctx context.Context) error
 NewError creates a new HTTPError instance with an optional message.
 
 ```go title="Signature"
-func NewError(code int, message ...string) *Error
+func NewError(code int, message ...any) *Error
 ```
 
 ```go title="Example"
 app.Get("/", func(c fiber.Ctx) error {
-    return fiber.NewError(782, "Custom error message")
+    return fiber.NewError(782, "Custom error %s", "message")
 })
 ```
 

docs/guide/error-handling.md

@@ -61,7 +61,7 @@ app.Get("/", func(c fiber.Ctx) error {
     return fiber.ErrServiceUnavailable
 
     // 503 On vacation!
-    return fiber.NewError(fiber.StatusServiceUnavailable, "On vacation!")
+    return fiber.NewError(fiber.StatusServiceUnavailable, "On %s", "vacation!")
 })
 ```