Expand documentation.

Author: pp-mo

docs/src/further_topics/index.rst

@@ -15,6 +15,7 @@ Extra information on specific technical issues.
    lenient_maths
    um_files_loading
    missing_data_handling
+   dataless_cubes
    netcdf_io
    dask_best_practices/index
    ugrid/index

docs/src/whatsnew/latest.rst

@@ -40,6 +40,14 @@ This document explains the changes made to Iris for this release
    :func:`~iris.fileformats.netcdf.saver.save_mesh` also supports ``zlib``
    compression. (:issue:`6565`, :pull:`6728`)
 
+#. `@pp-mo`_ added the ability to merge dataless cubes.  This also means they can be
+   re-loaded normally with :meth:`iris.load`.  See: :ref:`dataless_merge`.
+   (:issue:`5770`, :pull:`6581`)
+
+#. `@pp-mo`_ added a documentation section on dataless cubes.
+   See: :ref:`dataless-cubes`.
+   (:issue:`XXX`, :pull:`XXX`)
+
 
 🐛 Bugs Fixed
 =============

lib/iris/tests/integration/merge/test_merge.py

@@ -53,8 +53,7 @@ def mangle_cubelist(cubelist, dataless_option):
             or dataless_option == "dataless_all"
         ):
             # Make this one dataless
-            cube = cube.copy()
-            cube.data = None
+            cube = cube.copy(iris.DATALESS)
 
         result.append(cube)