L2SS-909: Do not allow writes of smaller arrays

tangostationcontrol/tangostationcontrol/clients/attribute_wrapper.py

 from operator import mul
 from functools import reduce
 
+import numpy
 from tango.server import attribute
 from tango import AttrWriteType, AttReqType
 
@@ -40,6 +41,21 @@ class attribute_io(object):
     def cached_write_function(self, value):
         """ Writes the given value to the device, and updates the cache. """
 
+        # flexible array sizes are not supported by all clients. make sure we only write arrays of maximum size.
+        if self.attribute_wrapper.write_max_shape and self.attribute_wrapper.shape != ():
+            if isinstance(value, numpy.ndarray):
+                value_shape = value.shape
+            else:
+                if len(value) > 0 and isinstance(value[0], list):
+                    # nested list
+                    value_shape = (len(value), len(value[0]))
+                else:
+                    # straight list
+                    value_shape = (len(value),)
+
+            if value_shape != self.attribute_wrapper.shape:
+                raise ValueError(f"Tried writing an array of shape {value_shape} into an attribute of shape {self.attribute_wrapper.shape}")
+
         self.write_function(value)
         self.cached_value = value
 
@@ -77,20 +93,30 @@ class attribute_wrapper(attribute):
             max_dim_x = 1
             max_dim_y = 0
             dtype = datatype
+            shape = ()
         elif len(dims) == 1:
             max_dim_x = dims[0]
             max_dim_y = 0
             dtype = (datatype,)
+            shape = (max_dim_x,)
         elif len(dims) == 2:
             max_dim_x = dims[1]
             max_dim_y = dims[0]
             dtype = ((datatype,),)
+            shape = (max_dim_y, max_dim_x)
         else:
             # >2D arrays collapse into the X and Y dimensions. The Y (major) dimension mirrors the first dimension given, the
             # rest collapses into the X (minor) dimension.
             max_dim_x = reduce(mul, dims[1:])
             max_dim_y = dims[0]
             dtype = ((datatype,),)
+            shape = (max_dim_y, max_dim_x)
+
+        # actual shape of the data as it is read/written
+        self.shape = shape
+
+        # force maximum shape to be written (do not accept writes with shapes smaller than the maximum for each dimension)
+        self.write_max_shape = True
 
         if access == AttrWriteType.READ_WRITE:
             """ If the attribute is of READ_WRITE type, assign the write and read functions to it"""