L2SS-281: Dim (1,0) is by definition a scalar according to PyTango. Honour this.

L2SS-244: Dim (1,0) is by definition a scalar according to PyTango. Honour this.

(cherry picked from commit d487f383)

devices/util/attribute_wrapper.py

@@ -14,18 +14,20 @@ class attribute_wrapper(attribute):
     Wraps all the attributes in a wrapper class to manage most of the redundant code behind the scenes
     """
 
-    def __init__(self, comms_annotation=None, datatype=None, dims=None, access=AttrWriteType.READ, init_value=None, **kwargs):
+    def __init__(self, comms_annotation=None, datatype=None, dims=(1,), access=AttrWriteType.READ, init_value=None, **kwargs):
         """
         wraps around the tango Attribute class. Provides an easier interface for 1d or 2d arrays. Also provides a way to abstract
         managing the communications interface.
 
         comms_annotation: data passed along to the attribute. can be given any form of data. handling is up to client implementation
         datatype: any numpy datatype
-        dims: dimensions of the attribute as a tuple, or None for a scalar.
+        dims: dimensions of the attribute as a tuple, or (1,) for a scalar.
         init_value: value
         """
 
-        # ensure the type is a numpy array
+        # ensure the type is a numpy array.
+        # see also https://pytango.readthedocs.io/en/stable/server_api/server.html?highlight=devlong#module-tango.server for 
+        # more details about type conversion Python/numpy -> PyTango
         if "numpy" not in str(datatype) and datatype != str:
             raise TypeError("Attribute needs to be a Tango-supported numpy or str type, but has type \"%s\"" % (datatype,))
 
@@ -33,7 +35,7 @@ class attribute_wrapper(attribute):
         self.numpy_type = datatype  # tango changes our attribute to their representation (E.g numpy.int64 becomes "DevLong64")
 
         self.init_value = init_value
-        max_dim_y = 0
+        is_scalar = dims == (1,)
 
         # tango doesn't recognise numpy.str_, for consistencies sake we convert it here and hide this from the top level
         # NOTE: discuss, idk if this is an important detail somewhere else
@@ -41,8 +43,12 @@ class attribute_wrapper(attribute):
             datatype = str
 
         # check if not scalar
-        if isinstance(dims, tuple):
-
+        if is_scalar:
+            # scalar, just set the single dimension.
+            # Tango defines a scalar as having dimensions (1,0), see https://pytango.readthedocs.io/en/stable/server_api/attribute.html
+            max_dim_x = 1
+            max_dim_y = 0
+        else:
             # get first dimension
             max_dim_x = dims[0]
 
@@ -55,8 +61,7 @@ class attribute_wrapper(attribute):
                 # wrap the datatype tuple in another tuple for 2d arrays/images
                 datatype = (datatype,)
             else:
-            # scalar, just set the single dimension
-            max_dim_x = 1
+                max_dim_y = 0
 
         if access == AttrWriteType.READ_WRITE:
             """ if the attribute is of READ_WRITE type, assign the RW and write function to it"""