support encoding variant of null array

Author: oroulet

opcua/ua/uatypes.py

@@ -821,10 +821,11 @@ def __str__(self):
     def to_binary(self):
         b = []
         encoding = self.VariantType.value & 0b111111
-        if type(self.Value) in (list, tuple):
+        if self.is_array or type(self.Value) in (list, tuple):
+            self.is_array = True
+            encoding = uabin.set_bit(encoding, 7)
             if self.Dimensions is not None:
                 encoding = uabin.set_bit(encoding, 6)
-            encoding = uabin.set_bit(encoding, 7)
             b.append(uabin.Primitives.UInt8.pack(encoding))
             b.append(uabin.pack_uatype_array(self.VariantType, flatten(self.Value)))
             if self.Dimensions is not None:
@@ -842,8 +843,6 @@ def from_binary(data):
         encoding = ord(data.read(1))
         int_type = encoding & 0b00111111
         vtype = datatype_to_varianttype(int_type)
-        if vtype == VariantType.Null:
-            return Variant(None, vtype, encoding)
         if uabin.test_bit(encoding, 7):
             value = uabin.unpack_uatype_array(vtype, data)
             array = True
@@ -886,7 +885,9 @@ def flatten_and_get_shape(mylist):
 
 
 def flatten(mylist):
-    if len(mylist) == 0:
+    if mylist is None:
+        return None
+    elif len(mylist) == 0:
         return mylist
     while isinstance(mylist[0], (list, tuple)):
         mylist = [item for sublist in mylist for item in sublist]

tests/tests_unit.py

@@ -25,6 +25,19 @@ class TestUnit(unittest.TestCase):
     Simple unit test that do not need to setup a server or a client
     '''
 
+    def test_variant_array_none(self):
+        v = ua.Variant(None, varianttype=ua.VariantType.Int32, is_array=True)
+        data = v.to_binary()
+        v2 = ua.Variant.from_binary(ua.utils.Buffer(data))
+        self.assertEqual(v, v2)
+        self.assertTrue(v2.is_array)
+
+        v = ua.Variant(None, varianttype=ua.VariantType.Null, is_array=True)
+        data = v.to_binary()
+        v2 = ua.Variant.from_binary(ua.utils.Buffer(data))
+        self.assertEqual(v, v2)
+        self.assertTrue(v2.is_array)
+
     def test_custom_structs(self):
         xmlpath = "tests/example.bsd"
         c = StructGenerator(xmlpath, "structures.py")