config: raise on setting mistyped or non-existent ConfigVar

electrum/simple_config.py

@@ -244,6 +244,8 @@ class SimpleConfig(Logger):
         self.amt_precision_post_satoshi = self.BTC_AMOUNTS_PREC_POST_SAT
         self.amt_add_thousands_sep = self.BTC_AMOUNTS_ADD_THOUSANDS_SEP
 
+        self._init_done = True
+
     def list_config_vars(self) -> Sequence[str]:
         return list(sorted(_config_var_from_key.keys()))
 
@@ -897,6 +899,21 @@ class SimpleConfig(Logger):
     def get_decimal_point(self):
         return self.decimal_point
 
+    def __setattr__(self, name, value):
+        """Disallows setting instance attributes outside __init__.
+
+        The point is to make the following code raise:
+        >>> config.NETORK_AUTO_CONNECTT = False
+        (i.e. catch mistyped or non-existent ConfigVars)
+        """
+        # If __init__ not finished yet, or this field already exists, set it:
+        if not getattr(self, "_init_done", False) or hasattr(self, name):
+            return super().__setattr__(name, value)
+        raise AttributeError(
+            f"Tried to define new instance attribute for config: {name=!r}. "
+            "Did you perhaps mistype a ConfigVar?"
+        )
+
     @cached_property
     def cv(config):
         """Allows getting a reference to a config variable without dereferencing it.

tests/test_simple_config.py

@@ -136,6 +136,12 @@ class Test_SimpleConfig(ElectrumTestCase):
             # revert:
             config.NETWORK_SERVER = None
 
+    def test_configvars_setter_catches_typo(self):
+        config = SimpleConfig(self.options)
+        assert not hasattr(config, "NETORK_AUTO_CONNECTT")
+        with self.assertRaises(AttributeError):
+            config.NETORK_AUTO_CONNECTT = False
+
     def test_configvars_get_default_value(self):
         config = SimpleConfig(self.options)
         self.assertEqual(MAX_MSG_SIZE_DEFAULT, config.cv.NETWORK_MAX_INCOMING_MSG_SIZE.get_default_value())