allow filename for mp3decoder.file property

Author: FoamyGuy

shared-bindings/audiomp3/MP3Decoder.c

@@ -139,7 +139,7 @@ static void check_for_deinit(audiomp3_mp3file_obj_t *self) {
 //|
 //  Provided by context manager helper.
 
-//|     file: typing.BinaryIO
+//|     file: Union[str, typing.BinaryIO] The name of a mp3 file (preferred) or an already opened mp3 file.
 //|     """File to play back."""
 //|
 static mp_obj_t audiomp3_mp3file_obj_get_file(mp_obj_t self_in) {
@@ -152,6 +152,9 @@ MP_DEFINE_CONST_FUN_OBJ_1(audiomp3_mp3file_get_file_obj, audiomp3_mp3file_obj_ge
 static mp_obj_t audiomp3_mp3file_obj_set_file(mp_obj_t self_in, mp_obj_t stream) {
     audiomp3_mp3file_obj_t *self = MP_OBJ_TO_PTR(self_in);
     check_for_deinit(self);
+    if (mp_obj_is_str(stream)) {
+        stream = mp_call_function_2(MP_OBJ_FROM_PTR(&mp_builtin_open_obj), stream, MP_ROM_QSTR(MP_QSTR_rb));
+    }
     const mp_stream_p_t *stream_p = mp_get_stream_raise(stream, MP_STREAM_OP_READ);
 
     if (stream_p->is_text) {