Resolve empty container types as the generic form of the container

Signed-off-by: Adam Glustein <[email protected]>

csp/impl/types/instantiation_type_resolver.py

@@ -557,10 +557,7 @@ def _resolve_tvar_container_internal_types(self, tvar, container_typ, arg, raise
             else:
                 return False
         if len(arg) == 0:
-            if raise_on_error:
-                raise ContainerTypeVarResolutionError(self._function_name, tvar, arg)
-            else:
-                return None
+            return container_typ
         res = None
         if isinstance(arg, set):
             first_val = arg.__iter__().__next__()

csp/tests/test_type_checking.py

@@ -314,13 +314,8 @@ def graph():
                     },
                 )
             l_good = csp.const.using(T={int: float})({})
-            with self.assertRaisesRegex(
-                TypeError,
-                "Unable to resolve container type for type variable T explicit value must have"
-                + " uniform values and be non empty.*",
-            ):
-                # Passing a Dummy value instead of expected float
-                l_bad = csp.const({})
+            l_also_good = csp.const({})
+            self.assertEqual(l_also_good.tstype.typ, dict)
 
             l_good = csp.const.using(T={int: float})({2: 1})
             l_good = csp.const.using(T={int: float})({2: 1.0})
@@ -377,13 +372,8 @@ def graph():
                 typed_ts_and_scalar_generic(l_i, [1, 2], TestTypeChecking.Dummy())
 
             l_good = csp.const.using(T=[int])([])
-            with self.assertRaisesRegex(
-                TypeError,
-                "Unable to resolve container type for type variable T explicit value must have"
-                + " uniform values and be non empty.*",
-            ):
-                # Passing a Dummy value instead of expected float
-                l_bad = csp.const([])
+            l_also_good = csp.const([])
+            self.assertEqual(l_also_good.tstype.typ, list)
 
         csp.run(graph, starttime=datetime(2020, 2, 7, 9), endtime=datetime(2020, 2, 7, 9, 1))
 
@@ -434,13 +424,8 @@ def graph():
                 typed_ts_and_scalar_generic(l_i, {1, 2}, TestTypeChecking.Dummy())
 
             l_good = csp.const.using(T={int})(set())
-            with self.assertRaisesRegex(
-                TypeError,
-                "Unable to resolve container type for type variable T explicit value must have"
-                + " uniform values and be non empty.*",
-            ):
-                # Passing a Dummy value instead of expected float
-                l_bad = csp.const({})
+            l_also_good = csp.const(set())
+            self.assertEqual(l_also_good.tstype.typ, set)
 
         csp.run(graph, starttime=datetime(2020, 2, 7, 9), endtime=datetime(2020, 2, 7, 9, 1))
 
@@ -612,6 +597,21 @@ def test_pickle_type_resolver_errors(self):
             pickled = pickle.loads(pickle.dumps(err))
             self.assertEqual(str(err), str(pickled))
 
+    def test_empty_containers(self):
+        def g():
+            x = csp.const([])
+            y = csp.const(set())
+            z = csp.const(dict())
+
+            csp.add_graph_output("x", x)
+            csp.add_graph_output("y", y)
+            csp.add_graph_output("z", z)
+
+        res = csp.run(g, starttime=datetime(2020, 1, 1), endtime=timedelta())
+        self.assertEqual(res["x"][0][1], [])
+        self.assertEqual(res["y"][0][1], set())
+        self.assertEqual(res["z"][0][1], {})
+
 
 if __name__ == "__main__":
     unittest.main()