fix(io): materialize transition validators from dict definitions

create_machine_class_from_definition threaded cond/unless/on/before/after
into Transition(), but dropped validators — so a 'validators' entry in a
dict/JSON definition was silently ignored and never ran at send(). The
TransitionDict TypedDict also mistyped validators as bool.

Pass validators through to Transition() and fix the type to the same
callback-spec union as cond/unless. Adds a regression test proving a
definition-supplied validator runs (and aborts) on send().

Closes #<issue>.

Signed-off-by: Christian Sentis <christian.sentis@icloud.com>

Author: csentis

statemachine/io/class_factory.py

@@ -35,7 +35,7 @@ class TransitionDict(TypedDict, total=False):
     event: "str | None"
     internal: bool
     initial: bool
-    validators: bool
+    validators: "str | ActionProtocol | Sequence[str] | Sequence[ActionProtocol]"
     cond: "str | ActionProtocol | Sequence[str] | Sequence[ActionProtocol]"
     unless: "str | ActionProtocol | Sequence[str] | Sequence[ActionProtocol]"
     on: "str | ActionProtocol | Sequence[str] | Sequence[ActionProtocol]"
@@ -204,6 +204,7 @@ def create_machine_class_from_definition(
                     "event": transition_event_name,
                     "internal": transition_data.get("internal"),
                     "initial": transition_data.get("initial"),
+                    "validators": transition_data.get("validators"),
                     "cond": transition_data.get("cond"),
                     "unless": transition_data.get("unless"),
                     "on": transition_data.get("on"),

tests/test_io.py

@@ -1,5 +1,6 @@
 """Tests for statemachine.io module (dictionary-based state machine definitions)."""
 
+import pytest
 from statemachine.io import create_machine_class_from_definition
 from statemachine.io.class_factory import _parse_history
 
@@ -44,3 +45,34 @@ def test_transition_with_both_parent_and_own_event_name(self):
         event_ids = sorted(e.id for e in sm.events)
         assert "parent_evt" in event_ids
         assert "sub_evt" in event_ids
+
+
+class TestTransitionValidators:
+    """A ``validators`` entry in a transition definition must be materialized
+    onto the Transition (the explicit-rejection channel), not silently dropped.
+    """
+
+    def test_validators_from_definition_run_on_send(self):
+        class Rejected(Exception):
+            pass
+
+        def reject(*args, **kwargs):
+            raise Rejected("not allowed")
+
+        sm_cls = create_machine_class_from_definition(
+            "ValidatedMachine",
+            states={
+                "s1": {
+                    "initial": True,
+                    "on": {"go": [{"target": "s2", "validators": reject}]},
+                },
+                "s2": {"final": True},
+            },
+        )
+        sm = sm_cls()
+
+        # Without the validator being materialized, send() would succeed and
+        # the machine would land in s2. With it, the validator aborts.
+        with pytest.raises(Rejected):
+            sm.send("go")
+        assert sm.current_state.id == "s1"