Return None for a missing subnet instead of asserting in subtensor getters

bittensor/core/subtensor.py

@@ -900,7 +900,8 @@ def blocks_since_last_update(
         call: Optional[list[int]] = self.get_hyperparameter(
             param_name="LastUpdate", netuid=netuid, block=block
         )
-        assert call is not None
+        if call is None:
+            return None
         return None if len(call) == 0 else (block - int(call[uid]))
 
     def blocks_until_next_epoch(
@@ -973,15 +974,18 @@ def bonds(
 
         return bond_map
 
-    def commit_reveal_enabled(self, netuid: int, block: Optional[int] = None) -> bool:
+    def commit_reveal_enabled(
+        self, netuid: int, block: Optional[int] = None
+    ) -> Optional[bool]:
         """Check if commit-reveal mechanism is enabled for a given subnet at a specific block.
 
         Parameters:
             netuid: The unique identifier of the subnet for which to check the commit-reveal mechanism.
             block: The block number to query. If `None`, queries the current chain head.
 
         Returns:
-            True if commit-reveal mechanism is enabled, False otherwise.
+            True if commit-reveal mechanism is enabled, False otherwise, or `None` if the subnet
+            does not exist.
 
         Notes:
             - <https://docs.learnbittensor.org/glossary#commit-reveal>
@@ -990,10 +994,11 @@ def commit_reveal_enabled(self, netuid: int, block: Optional[int] = None) -> boo
         call: Optional[bool] = self.get_hyperparameter(
             param_name="CommitRevealWeightsEnabled", block=block, netuid=netuid
         )
-        assert call is not None
+        if call is None:
+            return None
         return call
 
-    def difficulty(self, netuid: int, block: Optional[int] = None) -> int:
+    def difficulty(self, netuid: int, block: Optional[int] = None) -> Optional[int]:
         """Retrieves the 'Difficulty' hyperparameter for a specified subnet in the Bittensor network.
 
         This parameter determines the computational challenge required for neurons to participate in consensus and
@@ -1016,7 +1021,8 @@ def difficulty(self, netuid: int, block: Optional[int] = None) -> int:
         call: Optional[int] = self.get_hyperparameter(
             param_name="Difficulty", netuid=netuid, block=block
         )
-        assert call is not None
+        if call is None:
+            return None
         return int(call)
 
     def does_hotkey_exist(self, hotkey_ss58: str, block: Optional[int] = None) -> bool:

mypy.ini

@@ -1,6 +1,13 @@
 [mypy]
 ignore_missing_imports = True
 ignore_errors = True
+follow_imports_for_stubs = True
+
+[mypy-numpy.*]
+follow_imports = skip
+
+[mypy-numpy]
+follow_imports = skip
 
 [mypy-*.axon.*]
 ignore_errors = False

tests/unit_tests/test_subtensor.py

@@ -1989,6 +1989,27 @@ def test_difficulty_success(subtensor, mocker):
     assert result == int(mocked_get_hyperparameter.return_value)
 
 
+@pytest.mark.parametrize(
+    "getter,param_name,extra_kwargs",
+    [
+        ("difficulty", "Difficulty", {}),
+        ("commit_reveal_enabled", "CommitRevealWeightsEnabled", {}),
+        ("blocks_since_last_update", "LastUpdate", {"uid": 0}),
+    ],
+)
+def test_subnet_getter_returns_none_when_subnet_missing(
+    subtensor, mocker, getter, param_name, extra_kwargs
+):
+    """When the subnet/uid is absent, get_hyperparameter returns None; the getter must
+    return None (honouring its docstring) instead of raising AssertionError."""
+    mocker.patch.object(subtensor, "get_hyperparameter", return_value=None)
+    mocker.patch.object(subtensor, "get_current_block", return_value=1)
+
+    result = getattr(subtensor, getter)(netuid=999, block=1, **extra_kwargs)
+
+    assert result is None
+
+
 def test_recycle_success(subtensor, mocker):
     """Tests recycle method with successfully result."""
     # Preps