Update pp save rules to handle time means

lib/iris/fileformats/pp_save_rules.py

@@ -174,7 +174,14 @@ def _general_time_rules(cube, pp):
     if (time_coord is not None and
             time_coord.has_bounds() and
             clim_season_coord is None and
-            (fp_coord is not None or frt_coord is not None) and
+            cm_time_mean is not None):
+        pp.lbtim.ib = 2
+        pp.t1 = time_coord.units.num2date(time_coord.bounds[0, 0])
+        pp.t2 = time_coord.units.num2date(time_coord.bounds[0, 1])
+
+    if (time_coord is not None and
+            time_coord.has_bounds() and
+            clim_season_coord is None and
             cm_time_mean is not None and
             cm_time_mean.intervals != () and
             cm_time_mean.intervals[0].endswith('hour')):

lib/iris/tests/test_cube_to_pp.py

@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2010 - 2017, Met Office
+# (C) British Crown Copyright 2010 - 2018, Met Office
 #
 # This file is part of Iris.
 #
@@ -26,6 +26,7 @@
 import tempfile
 
 import cf_units
+import cftime
 import numpy as np
 
 import iris.coords
@@ -294,8 +295,8 @@ def test_lbvc(self):
             self.assertEqual(field.lbvc, lbvc)
             self.assertEqual(field.lblev, lblev)
             self.assertEqual(field.blev, blev)
-        
-        
+
+
 def fields_from_cube(cubes):
     """
     Return an iterator of PP fields generated from saving the given cube(s)

lib/iris/tests/unit/fileformats/pp/test_save.py

@@ -19,14 +19,17 @@
 from __future__ import (absolute_import, division, print_function)
 from six.moves import (filter, input, map, range, zip)  # noqa
 
+import cftime
+import cf_units
+
 # Import iris.tests first so that some things can be initialised before
 # importing anything else.
 import iris.tests as tests
 
 from iris.coords import DimCoord, CellMethod
 from iris.fileformats._ff_cross_references import STASH_TRANS
 import iris.fileformats.pp as pp
-from iris.fileformats.pp_save_rules import _lbproc_rules
+from iris.fileformats.pp_save_rules import _lbproc_rules, verify
 from iris.tests import mock
 import iris.tests.stock as stock
 
@@ -198,5 +201,140 @@ def test_maximum(self):
         self.assertEqual(lbproc, 8192)
 
 
+class TestTimeMean(tests.IrisTest):
+    '''
+    Tests that time mean cell method is converted to pp appropriately.
+
+    Pattern is pairs of tests - one with time mean method, and one without, to
+    show divergent behaviour.
+
+    '''
+    def test_t1_time_mean(self):
+        cube = _get_single_time_cube(set_time_mean=True)
+        tc = cube.coord(axis='t')
+        expected = tc.units.num2date(0)
+
+        with mock.patch('iris.fileformats.pp.PPField3',
+                        autospec=True) as pp_field:
+            verify(cube, pp_field)
+        actual = pp_field.t1
+
+        self.assertEqual(expected, actual)
+
+    def test_t1_no_time_mean(self):
+        cube = _get_single_time_cube()
+        tc = cube.coord(axis='t')
+        expected = tc.units.num2date(15)
+
+        with mock.patch('iris.fileformats.pp.PPField3',
+                        autospec=True) as pp_field:
+            verify(cube, pp_field)
+        actual = pp_field.t1
+
+        self.assertEqual(expected, actual)
+
+    def test_t2_time_mean(self):
+        cube = _get_single_time_cube(set_time_mean=True)
+        tc = cube.coord(axis='t')
+        expected = tc.units.num2date(30)
+
+        with mock.patch('iris.fileformats.pp.PPField3',
+                        autospec=True) as pp_field:
+            verify(cube, pp_field)
+        actual = pp_field.t2
+
+        self.assertEqual(expected, actual)
+
+    def test_t2_no_time_mean(self):
+        cube = _get_single_time_cube(set_time_mean=False)
+        expected = cftime.datetime(0, 0, 0)
+
+        with mock.patch('iris.fileformats.pp.PPField3',
+                        autospec=True) as pp_field:
+            verify(cube, pp_field)
+        actual = pp_field.t2
+        self.assertEqual(expected, actual)
+
+    def test_lbft_no_forecast_time(self):
+        # Different pattern here: checking that lbft hasn't been changed from
+        # the default value.
+        cube = _get_single_time_cube()
+        mock_lbft = mock.sentinel.lbft
+
+        with mock.patch('iris.fileformats.pp.PPField3',
+                        autospec=True) as pp_field:
+            pp_field.lbft = mock_lbft
+            verify(cube, pp_field)
+        actual = pp_field.lbft
+
+        assert(mock_lbft is actual)
+
+    def test_lbtim_no_time_mean(self):
+        cube = _get_single_time_cube()
+        expected_ib = 0
+        expected_ic = 2  # 360 day calendar
+
+        with mock.patch('iris.fileformats.pp.PPField3',
+                        autospec=True) as pp_field:
+            verify(cube, pp_field)
+        actual_ib = pp_field.lbtim.ib
+        actual_ic = pp_field.lbtim.ic
+
+        self.assertEqual(expected_ib, actual_ib)
+        self.assertEqual(expected_ic, actual_ic)
+
+    def test_lbtim_time_mean(self):
+        cube = _get_single_time_cube(set_time_mean=True)
+        expected_ib = 2  # Time mean
+        expected_ic = 2  # 360 day calendar
+
+        with mock.patch('iris.fileformats.pp.PPField3',
+                        autospec=True) as pp_field:
+            verify(cube, pp_field)
+        actual_ib = pp_field.lbtim.ib
+        actual_ic = pp_field.lbtim.ic
+
+        self.assertEqual(expected_ib, actual_ib)
+        self.assertEqual(expected_ic, actual_ic)
+
+    def test_lbproc_no_time_mean(self):
+        cube = _get_single_time_cube()
+        expected = 0
+
+        with mock.patch('iris.fileformats.pp.PPField3',
+                        autospec=True) as pp_field:
+            verify(cube, pp_field)
+        actual = pp_field.lbproc
+
+        self.assertEqual(expected, actual)
+
+    def test_lbproc_time_mean(self):
+        cube = _get_single_time_cube(set_time_mean=True)
+        expected = 128
+
+        with mock.patch('iris.fileformats.pp.PPField3',
+                        autospec=True) as pp_field:
+            verify(cube, pp_field)
+        actual = pp_field.lbproc
+
+        self.assertEqual(expected, actual)
+
+
+def _get_single_time_cube(set_time_mean=False):
+    cube = stock.realistic_3d()[0:1, :, :]
+    cube.remove_coord('time')
+    cube.remove_coord('forecast_period')
+    tc = DimCoord(
+        points=[15, ],
+        standard_name='time',
+        units=cf_units.Unit('days since epoch', calendar='360_day'),
+        bounds=[[0, 30], ],
+    )
+    cube.add_dim_coord(tc, 0)
+    if set_time_mean:
+        cube.cell_methods = (CellMethod("mean", coords='time'), )
+    return cube
+
+
 if __name__ == "__main__":
     tests.main()