Fix serve sanity checking

CHANGELOG.md

@@ -18,6 +18,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 ### Fixed
 
 
+- Fixed a bug where serve sanity checking would not be triggered using the latest PyTorchLightning version ([#493](https://github.com/PyTorchLightning/lightning-flash/pull/493))
+
+
 ## [0.4.0] - 2021-06-22
 
 ### Added

flash/core/trainer.py

@@ -87,8 +87,15 @@ def __init__(self, *args, serve_sanity_check: bool = False, **kwargs):
 
         self.serve_sanity_check = serve_sanity_check
 
+    def _run_sanity_check(self, ref_model):
+        if hasattr(super(), "_run_sanity_check"):
+            super()._run_sanity_check(ref_model)
+
+        self.run_sanity_check(ref_model)
+
     def run_sanity_check(self, ref_model):
-        super().run_sanity_check(ref_model)
+        if hasattr(super(), "run_sanity_check"):
+            super().run_sanity_check(ref_model)
 
         if self.serve_sanity_check and ref_model.is_servable and _SERVE_AVAILABLE:
             ref_model.run_serve_sanity_check()