Merge pull request #113 from LSSTDESC/Validation

Validation step

ceci/stage.py

@@ -148,6 +148,13 @@ def get_aliased_tag(self, tag):
     def run(self):  # pragma: no cover
         """Run the stage and return the execution status"""
         raise NotImplementedError("run")
+
+    def validate(self):
+        """Check that the inputs actually have the data needed for execution,
+        This is called before the run method. It is an optional stage, meant
+        for checking that the input to the stage is actual in the form and
+        shape needed before an expensive run is executed."""
+        pass 
 
     def load_configs(self, args):
         """
@@ -661,6 +668,18 @@ def execute(cls, args, comm=None):
         if args.memmon:  # pragma: no cover
             monitor = MemoryMonitor.start_in_thread(interval=args.memmon)
 
+        # Now we try to see if the validation step has been changed,
+        # if it has then we will run the validation step, and raise any errors
+        try:
+            stage.validate()
+        except Exception as error:
+            if stage.rank==0:
+                print(f"Looks like there is an validation error in: {cls.name}",
+                        "the input data for this stage did not pass the checks implemented on it.")
+                print(error)
+            raise
+
+
         try:
             stage.run()
         except Exception as error:  # pragma: no cover