add typehints for required CS attributes

bsb/storage/interfaces.py

@@ -11,6 +11,10 @@
 from .._util import obj_str_insert, immutable
 
 
+if typing.TYPE_CHECKING:
+    from ..cell_types import CellType
+
+
 @config.pluggable(key="engine", plugin_name="storage engine")
 class StorageNode:
     root = config.slot()
@@ -364,6 +368,10 @@ def __init__(self, engine, cell_type):
         self._type = cell_type
         self._tag = cell_type.name
 
+    @abc.abstractmethod
+    def __len__(self):
+        pass
+
     @obj_str_insert
     def __repr__(self):
         cell_type = self.cell_type
@@ -887,6 +895,15 @@ class ConnectivitySet(Interface):
     connections.
     """
 
+    # The following attributes must be set on each ConnectivitySet by the engine:
+    tag: str
+    pre_type: "CellType"
+    post_type: "CellType"
+
+    @abc.abstractmethod
+    def __len__(self):
+        pass
+
     @classmethod
     @abc.abstractmethod
     def create(cls, engine, tag):

bsb/unittest/engines.py

@@ -478,6 +478,18 @@ def test_require(self):
             "must exist after require",
         )
 
+    def test_attrs(self):
+        ct = self.network.cell_types.add(
+            "new_cell", dict(spatial=dict(radius=2, density=1e-3))
+        )
+        self.network.require_connectivity_set(
+            ct, self.network.cell_types.test_cell, "test"
+        )
+        cs = self.storage._ConnectivitySet(self.storage._engine, "test")
+        for attr in ("tag", "pre_type", "post_type"):
+            with self.subTest(attr=attr):
+                self.assertTrue(hasattr(cs, attr), f"CS must have `{attr}` attr")
+
     def test_io(self):
         # Test that connections can be stored over chunked layout and can be loaded again.
         cs = self.network.get_connectivity_set("all_to_all")