fix: avoid instantiating StateChart class in diagram extraction

The extract function now uses the class directly (never instantiates it)
since all structural metadata (states, transitions, name) is already
available on the class thanks to the metaclass. Active-state highlighting
is only produced when an instance is passed.

Author: fgmacedo

statemachine/contrib/diagram/extract.py

@@ -1,5 +1,6 @@
 from typing import TYPE_CHECKING
 from typing import List
+from typing import Union
 
 from .model import DiagramAction
 from .model import DiagramGraph
@@ -11,6 +12,9 @@
     from statemachine.state import State
     from statemachine.statemachine import StateChart
 
+    # A StateChart class or instance — both expose the same structural metadata.
+    MachineRef = Union["StateChart", "type[StateChart]"]
+
 
 def _determine_state_type(state: "State") -> StateType:
     from statemachine.state import HistoryState
@@ -27,7 +31,7 @@ def _determine_state_type(state: "State") -> StateType:
     return StateType.REGULAR
 
 
-def _actions_getter(machine: "StateChart"):
+def _actions_getter(machine: "MachineRef"):
     from statemachine.statemachine import StateChart
 
     if isinstance(machine, StateChart):
@@ -67,7 +71,7 @@ def _extract_state_actions(state: "State", getter) -> List[DiagramAction]:
 
 def _extract_state(
     state: "State",
-    machine: "StateChart",
+    machine: "MachineRef",
     getter,
     active_values: set,
 ) -> DiagramState:
@@ -131,9 +135,14 @@ def _extract_all_transitions(states, getter) -> List[DiagramTransition]:
     return result
 
 
-def extract(machine_or_class: "StateChart | type") -> DiagramGraph:
+def extract(machine_or_class: "MachineRef") -> DiagramGraph:
     """Extract a DiagramGraph IR from a state machine instance or class.
 
+    Accepts either a class or an instance.  The class is **never** instantiated
+    — all structural metadata (states, transitions, name) is available on the
+    class itself thanks to the metaclass.  Active-state highlighting is only
+    produced when an *instance* is passed.
+
     Args:
         machine_or_class: A StateMachine/StateChart instance or class.
 
@@ -142,17 +151,17 @@ def extract(machine_or_class: "StateChart | type") -> DiagramGraph:
     """
     from statemachine.statemachine import StateChart
 
-    is_class = isinstance(machine_or_class, type)
-    if is_class and issubclass(machine_or_class, StateChart):  # type: ignore[arg-type]
-        machine = machine_or_class()  # type: ignore[operator]
-    elif isinstance(machine_or_class, StateChart):
+    if isinstance(machine_or_class, StateChart):
+        machine: "MachineRef" = machine_or_class
+    elif isinstance(machine_or_class, type) and issubclass(machine_or_class, StateChart):
         machine = machine_or_class
     else:
         raise TypeError(f"Expected a StateChart instance or class, got {type(machine_or_class)}")
 
     getter = _actions_getter(machine)
+
     active_values: set = set()
-    if not is_class and hasattr(machine, "configuration_values"):
+    if isinstance(machine, StateChart) and hasattr(machine, "configuration_values"):
         active_values = set(machine.configuration_values)
 
     states: List[DiagramState] = []