[planner] try bends=2 before bends=(2, 4)

masque/builder/planner/planner.py

@@ -50,6 +50,7 @@ from .interface import (
     PreparedRouteResult,
     RoutePlanningError,
     RoutePortContext,
+    route_error_is_fatal,
     )
 
 
@@ -908,6 +909,12 @@ class RoutingPlanner:
 
     TRACE_INTO_MAX_BENDS: int = 4
 
+    def trace_into_bend_budgets(self, family: PrimitiveKind) -> tuple[int, ...]:
+        """Return staged trace_into bend budgets for the route rotation parity."""
+        if family == 'bend':
+            return tuple(budget for budget in (1, 3) if budget <= self.TRACE_INTO_MAX_BENDS)
+        return tuple(budget for budget in (2, 4) if budget <= self.TRACE_INTO_MAX_BENDS)
+
     def plan_leg(
             self,
             family: PrimitiveKind,
@@ -1197,17 +1204,30 @@ class RoutingPlanner:
         desired.rotation = port_dst.rotation - pi
         desired.ptype = out_ptype
         family, length, jog, ccw = self.trace_into_spec(context_src.port, desired)
-        leg = self.plan_leg(
-            family,
-            context_src,
-            length=length,
-            jog=jog,
-            ccw=ccw,
-            plug_into=portspec_dst if plug_destination else None,
-            constrain_jog=family == 'bend',
-            max_bends=self.TRACE_INTO_MAX_BENDS,
-            **(dict(kwargs) | {'out_ptype': out_ptype}),
-            )
+        leg = None
+        last_error: Exception | None = None
+        for max_bends in self.trace_into_bend_budgets(family):
+            try:
+                leg = self.plan_leg(
+                    family,
+                    context_src,
+                    length=length,
+                    jog=jog,
+                    ccw=ccw,
+                    plug_into=portspec_dst if plug_destination else None,
+                    constrain_jog=family == 'bend',
+                    max_bends=max_bends,
+                    **(dict(kwargs) | {'out_ptype': out_ptype}),
+                    )
+                break
+            except (BuildError, NotImplementedError) as err:
+                if route_error_is_fatal(err):
+                    raise
+                last_error = err
+        if leg is None:
+            if last_error is not None:
+                raise last_error
+            raise BuildError('No legal primitive offer for trace_into route')
         renames = ((thru, context_src.portspec),) if thru is not None else ()
         return self.prepared_result_from_legs(
             (leg,),