From 168321bdef2a9ac2b10157dbc27b97eed27c76a7 Mon Sep 17 00:00:00 2001
From: Stephan Finkensieper <stephan.finkensieper@dwd.de>
Date: Fri, 25 Oct 2019 13:54:56 +0000
Subject: [PATCH] Fix handling of header attributes in CF writer

Header attributes equal to zero were not included in the global
nc attributes.
---
 satpy/tests/writer_tests/test_cf.py | 13 +++++++++----
 satpy/writers/cf_writer.py          |  3 ++-
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/satpy/tests/writer_tests/test_cf.py b/satpy/tests/writer_tests/test_cf.py
index 6e47b0f231..d3af850ace 100644
--- a/satpy/tests/writer_tests/test_cf.py
+++ b/satpy/tests/writer_tests/test_cf.py
@@ -324,14 +324,19 @@ def test_header_attrs(self):
                                                     end_time=end_time))
         with TempFile() as filename:
             header_attrs = {'sensor': 'SEVIRI',
-                            'orbit': None}
+                            'orbit': None,
+                            'empty': [],
+                            'num': 1.1,
+                            'zero': 0}
             scn.save_datasets(filename=filename,
                               header_attrs=header_attrs,
                               writer='cf')
             with xr.open_dataset(filename) as f:
-                self.assertTrue(f.attrs['sensor'] == 'SEVIRI')
-                self.assertTrue('sensor' in f.attrs.keys())
-                self.assertTrue('orbit' not in f.attrs.keys())
+                self.assertEqual(f.attrs['sensor'], 'SEVIRI')
+                self.assertEqual(f.attrs['num'], 1.1)
+                self.assertEqual(f.attrs['zero'], 0)
+                self.assertNotIn('orbit', f.attrs)
+                self.assertNotIn('empty', f.attrs)
 
     def get_test_attrs(self):
         """Create some dataset attributes for testing purpose.
diff --git a/satpy/writers/cf_writer.py b/satpy/writers/cf_writer.py
index eaa7e7da86..e94ab8c043 100644
--- a/satpy/writers/cf_writer.py
+++ b/satpy/writers/cf_writer.py
@@ -638,7 +638,8 @@ def save_datasets(self, datasets, filename=None, groups=None, header_attrs=None,
 
         root = xr.Dataset({}, attrs={'history': 'Created by pytroll/satpy on {}'.format(datetime.utcnow())})
         if header_attrs is not None:
-            root.attrs.update({k: v for k, v in header_attrs.items() if v})
+            root.attrs.update({k: v for k, v in header_attrs.items()
+                               if (np.isscalar(v) and v is not None) or v})
         if groups is None:
             # Groups are not CF-1.7 compliant
             root.attrs['Conventions'] = CF_VERSION