Improve control over repr parameters when empty.

law/task/base.py

@@ -434,6 +434,7 @@ class Task(six.with_metaclass(Register, BaseTask)):
     exclude_index = True
     exclude_params_req = set()
     exclude_params_repr = set()
+    exclude_params_repr_empty = set()
 
     @classmethod
     def req_params(cls, inst, _exclude=None, _prefer_cli=None, **kwargs):
@@ -595,8 +596,14 @@ def _repr_params(self, all_params=False):
         # build a map "name -> value" for all significant parameters
         params = OrderedDict()
         for name, param in self.get_params():
-            if param.significant and not multi_match(name, exclude):
-                params[name] = getattr(self, name)
+            value = getattr(self, name)
+            include = (
+                param.significant and
+                not multi_match(name, exclude) and
+                (name not in self.exclude_params_repr_empty or value)
+            )
+            if include:
+                params[name] = value
 
         return params
 

law/workflow/base.py

@@ -481,8 +481,10 @@ def _repr_params(self, *args, **kwargs):
 
         if self.is_workflow():
             # when this is a workflow, add the workflow type
-            if "workflow" not in params:
-                params["workflow"] = self.workflow
+            params.setdefault("workflow", self.workflow)
+            # skip branches when empty
+            if not params.get("branches"):
+                params.pop("branches", None)
         else:
             # when this is a branch, remove workflow parameters
             for param in self.exclude_params_branch: