refactor(router): fold block-and-fallback decision into one method

Collapse the SIM103-flagged if/return into a direct boolean return and
cover the folded method by name so the router coverage gate stays green

litellm/router.py

@@ -10019,11 +10019,9 @@ class Router:
         deployments: Final = self.get_model_list(model_name=model_name, team_id=team_id) or []
         if not self._are_all_deployments_blocked(deployments):
             return False
-        if reachable_fallbacks is not None and self._has_reachable_fallback(
+        return reachable_fallbacks is None or not self._has_reachable_fallback(
             model_name=model_name, fallbacks=reachable_fallbacks, team_id=team_id
-        ):
-            return False
-        return True
+        )
 
     async def async_get_fully_unhealthy_model_names(self) -> set[str]:
         """

tests/test_litellm/test_router_block_helpers.py

@@ -145,3 +145,39 @@ class TestHasReachableFallback:
             ]
         )
         assert router._has_reachable_fallback("primary", fallbacks=["fallback"]) is True
+
+
+class TestIsBlockedWithoutReachableFallback:
+    def test_blocked_and_no_fallback_returns_true(self):
+        router = Router(model_list=[_deployment("primary", "p0", blocked=True)])
+        assert router._is_blocked_without_reachable_fallback("primary", reachable_fallbacks=None, team_id=None) is True
+
+    def test_not_all_blocked_returns_false(self):
+        router = Router(model_list=[_deployment("primary", "p0", blocked=False)])
+        assert router._is_blocked_without_reachable_fallback("primary", reachable_fallbacks=None, team_id=None) is False
+
+    def test_blocked_with_reachable_fallback_returns_false(self):
+        router = Router(
+            model_list=[
+                _deployment("primary", "p0", blocked=True),
+                _deployment("fallback", "f0", blocked=False),
+            ]
+        )
+        reachable = [{"primary": ["fallback"]}]
+        assert (
+            router._is_blocked_without_reachable_fallback("primary", reachable_fallbacks=reachable, team_id=None)
+            is False
+        )
+
+    def test_blocked_with_fully_blocked_fallback_returns_true(self):
+        router = Router(
+            model_list=[
+                _deployment("primary", "p0", blocked=True),
+                _deployment("fallback", "f0", blocked=True),
+            ]
+        )
+        reachable = [{"primary": ["fallback"]}]
+        assert (
+            router._is_blocked_without_reachable_fallback("primary", reachable_fallbacks=reachable, team_id=None)
+            is True
+        )