Fix #5347 (#5349)

* fix unit multiplication bug

* docs linkcheck ignore biggus rtd url (#5351)

* add patch whatsnew

---------

Co-authored-by: Bill Little <[email protected]>

docs/src/conf.py

@@ -382,6 +382,7 @@ def _dotv(version):
  "http:https://www.esrl.noaa.gov/psd/data/gridded/conventions/cdc_netcdf_standard.shtml",
  "http:https://www.nationalarchives.gov.uk/doc/open-government-licence",
  "https://www.metoffice.gov.uk/",
+ "https://biggus.readthedocs.io/",
 ]
 
 # list of sources to exclude from the build.

docs/src/whatsnew/3.6.rst

@@ -55,6 +55,23 @@ This document explains the changes made to Iris for this release
  or feature requests for improving Iris. Enjoy!
 
 
+|iris_version| |build_date|
+===========================
+
+.. dropdown:: |iris_version| Patches
+ :color: primary
+ :icon: alert
+ :animate: fade-in
+
+ The patches in this release of Iris include:
+
+ 🐛 **Bugs Fixed**
+
+ #. `@stephenworsley`_ fixed :meth:`~iris.cube.Cube.convert_units` to allow unit
+ conversion of lazy data when using a `Distributed`_ scheduler.
+ (:issue:`5347`, :pull:`5349`)
+
+
 📢 Announcements
 ================
 
@@ -180,4 +197,5 @@ This document explains the changes made to Iris for this release
 .. _PEP-0621: https://peps.python.org/pep-0621/
 .. _pypa/build: https://pypa-build.readthedocs.io/en/stable/
 .. _NEP29: https://numpy.org/neps/nep-0029-deprecation_policy.html
-.. _Contributor Covenant: https://www.contributor-covenant.org/version/2/1/code_of_conduct/
+.. _Contributor Covenant: https://www.contributor-covenant.org/version/2/1/code_of_conduct/
+.. _Distributed: https://distributed.dask.org/en/stable/

lib/iris/cube.py

@@ -19,6 +19,7 @@
 from xml.dom.minidom import Document
 import zlib
 
+from cf_units import Unit
 import dask.array as da
 import numpy as np
 import numpy.ma as ma
@@ -1144,7 +1145,7 @@ def convert_units(self, unit):
  )
  if self.has_lazy_data():
  # Make fixed copies of old + new units for a delayed conversion.
- old_unit = self.units
+ old_unit = Unit(self.units)
  new_unit = unit
 
  pointwise_convert = partial(old_unit.convert, other=new_unit)

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

@@ -14,6 +14,8 @@
 from unittest import mock
 
 from cf_units import Unit
+import dask.array as da
+from distributed import Client
 import numpy as np
 import numpy.ma as ma
 import pytest
@@ -3012,6 +3014,14 @@ def test_preserves_lazy(self):
  self.assertTrue(cube.has_lazy_data())
  self.assertArrayAllClose(cube.data, real_data_ft)
 
+ def test_unit_multiply(self):
+ _client = Client()
+ cube = iris.cube.Cube(da.arange(1), units="m")
+ cube.units *= "s-1"
+ cube.convert_units("m s-1")
+ cube.data
+ _client.close()
+
 
 class Test__eq__data(tests.IrisTest):
  """Partial cube equality testing, for data type only."""