Add the pending future from ensemble builder to the history

autosklearn/automl.py

@@ -751,19 +751,21 @@ def fit(
         if proc_ensemble is not None:
             self.ensemble_performance_history = list(proc_ensemble.history)
 
-            # save the ensemble performance history file
-            if len(self.ensemble_performance_history) > 0:
-                pd.DataFrame(self.ensemble_performance_history).to_json(
-                        os.path.join(self._backend.internals_directory, 'ensemble_history.json'))
-
             if len(proc_ensemble.futures) > 0:
-                future = proc_ensemble.futures.pop()
                 # Now we need to wait for the future to return as it cannot be cancelled while it
                 # is running: https://stackoverflow.com/a/49203129
                 self._logger.info("Ensemble script still running, waiting for it to finish.")
-                future.result()
+                result = proc_ensemble.futures.pop().result()
+                if result:
+                    ensemble_history, _, _, _, _ = result
+                    self.ensemble_performance_history.extend(ensemble_history)
                 self._logger.info("Ensemble script finished, continue shutdown.")
 
+            # save the ensemble performance history file
+            if len(self.ensemble_performance_history) > 0:
+                pd.DataFrame(self.ensemble_performance_history).to_json(
+                        os.path.join(self._backend.internals_directory, 'ensemble_history.json'))
+
         if load_models:
             self._logger.info("Loading models...")
             self._load_models()