config: always use bytes() for default value

extmod/modtrezorconfig/modtrezorconfig.c

@@ -32,7 +32,7 @@ STATIC mp_obj_t mod_TrezorConfig_Config_make_new(const mp_obj_type_t *type, size
 
 /// def trezor.config.get(app: int, key: int) -> bytes:
 ///     '''
-///     Gets a value of given key for given app (or None if not set).
+///     Gets a value of given key for given app (or empty bytes if not set).
 ///     '''
 STATIC mp_obj_t mod_TrezorConfig_Config_get(mp_obj_t self, mp_obj_t app, mp_obj_t key) {
     uint8_t a = mp_obj_get_int(app);
@@ -41,8 +41,8 @@ STATIC mp_obj_t mod_TrezorConfig_Config_get(mp_obj_t self, mp_obj_t app, mp_obj_
     const void *val;
     uint32_t len;
     bool r = norcow_get(appkey, &val, &len);
-    if (!r) {
-        return mp_const_none;
+    if (!r || len == 0) {
+        return mp_const_empty_bytes;
     }
     vstr_t vstr;
     vstr_init_len(&vstr, len);

src/trezor/config.py

@@ -6,12 +6,14 @@ else:
     from TrezorConfig import Config
     _config = Config()
 
-def get(app, key, default=None):
-    v = _config.get(app, key)
-    return v if v else default
 
-def set(app, key, value):
+def get(app: int, key: int) -> bytes:
+    return _config.get(app, key)
+
+
+def set(app: int, key: int, value: bytes):
     return _config.set(app, key, value)
 
+
 def wipe():
     return _config.wipe()

src/trezor/config_mock.py

@@ -2,7 +2,8 @@
 
 import ustruct
 
-def Config():
+
+class Config:
 
     def __init__(self, filename):
         self._data = {}
@@ -25,8 +26,8 @@ def Config():
                 f.write(ustruct.pack('<HH', k, len(v)))
                 f.write(v)
 
-    def get(self, app_id, key, default=None):
-        return self._data.get((app_id << 8) | key, default)
+    def get(self, app_id, key):
+        return self._data.get((app_id << 8) | key, bytes())
 
     def set(self, app_id, key, value):
         self._data[(app_id << 8) | key] = value

tests/test_trezor.config.py

@@ -33,9 +33,8 @@ class TestConfig(unittest.TestCase):
         config.wipe()
         for _ in range(64):
             appid, key = random.uniform(256), random.uniform(256)
-           value = random.bytes(128)
-           value2 = config.get(appid, key, value)
-           self.assertEqual(value, value2)
+            value = config.get(appid, key)
+            self.assertEqual(value, bytes())
 
 if __name__ == '__main__':
     unittest.main()