made dataless copy opt-in behaviour

lib/iris/__init__.py

@@ -148,7 +148,6 @@ def __init__(
         datum_support=False,
         pandas_ndim=False,
         save_split_attrs=False,
-        dataless_cube=False,
     ):
         """Container for run-time options controls.
 
@@ -187,20 +186,18 @@ def __init__(
         self.__dict__["datum_support"] = datum_support
         self.__dict__["pandas_ndim"] = pandas_ndim
         self.__dict__["save_split_attrs"] = save_split_attrs
-        self.__dict__["dataless_cube"] = dataless_cube
 
         # TODO: next major release: set IrisDeprecation to subclass
         #  DeprecationWarning instead of UserWarning.
 
     def __repr__(self):
         # msg = ('Future(example_future_flag={})')
         # return msg.format(self.example_future_flag)
-        msg = "Future(datum_support={}, pandas_ndim={}, save_split_attrs={}, dataless_cubes={})"
+        msg = "Future(datum_support={}, pandas_ndim={}, save_split_attrs={})"
         return msg.format(
             self.datum_support,
             self.pandas_ndim,
             self.save_split_attrs,
-            self.dataless_cube,
         )
 
     # deprecated_options = {'example_future_flag': 'warning',}
@@ -846,4 +843,4 @@ def use_plugin(plugin_name):
     importlib.import_module(f"iris.plugins.{plugin_name}")
 
 
-MAINTAIN_DATA = "MAINTAINDATA"
+DATALESS_COPY = "NONE"

lib/iris/_data_manager.py

@@ -159,18 +159,15 @@ def _deepcopy(self, memo, data=None):
         """
         shape = None
         try:
-            if iris.FUTURE.dataless_cube and data is None:
-                shape = self.shape
-            elif (
-                iris.FUTURE.dataless_cube
-                and type(data) is str
-                and data == iris.MAINTAIN_DATA
-            ) or (data is None):
+            if data is None:
                 # Copy the managed data.
                 if self.has_lazy_data():
                     data = copy.deepcopy(self._lazy_array, memo)
                 else:
                     data = self._real_array.copy()
+            elif type(data) is str and data == iris.DATALESS_COPY:
+                shape = self.shape
+                data = None
             else:
                 # Check that the replacement data is valid relative to
                 # the currently managed data.

lib/iris/coords.py

@@ -2708,8 +2708,7 @@ def __deepcopy__(self, memo):  # numpydoc ignore=SS02
         """
         new_coord = copy.deepcopy(super(), memo)
         # Ensure points and bounds arrays are read-only.
-        if not (new_coord._values_dm.data is None and iris.FUTURE.dataless_cube):
-            new_coord._values_dm.data.flags.writeable = False
+        new_coord._values_dm.data.flags.writeable = False
         if new_coord._bounds_dm is not None:
             new_coord._bounds_dm.data.flags.writeable = False
         return new_coord

lib/iris/tests/unit/cube/test_Cube.py

@@ -2090,12 +2090,11 @@ def test_copy_new_data(self):
         _shared_utils.assert_array_equal(new_cube.data, new_data)
 
     def test_copy_remove_data(self):
-        with iris.FUTURE.context(dataless_cube=True):
-            cube = stock.simple_3d()
-            new_cube = cube.copy()
-            assert new_cube.metadata == cube.metadata
-            assert new_cube.data is None
-            assert new_cube.shape == cube.shape
+        cube = stock.simple_3d()
+        new_cube = cube.copy(iris.DATALESS_COPY)
+        assert new_cube.metadata == cube.metadata
+        assert new_cube.data is None
+        assert new_cube.shape == cube.shape
 
     def test__masked_emptymask(self):
         cube = Cube(ma.array([0, 1]))