generator: tweak how MultiStrOpt defaults are handled

If a MultiStrOpt default is set to None or [], the best thing to do is
just add:

  #multi_str_opt =

to the sample config file.

Change-Id: Ibaee466978870082be47a2135ae3f412d3efd623

2 files changed, 32 insertions, 3 deletions

diff --git a/oslo/config/generator.py b/oslo/config/generator.py
index 57c70bd..d5bdf13 100644
--- a/oslo/config/generator.py
+++ b/oslo/config/generator.py
@@ -186,8 +186,8 @@ class _OptFormatter(object):
         if isinstance(opt, cfg.MultiStrOpt):
             if opt.sample_default is not None:
                 defaults = opt.sample_default
-            elif opt.default is None:
-                defaults = ['<None>']
+            elif not opt.default:
+                defaults = ['']
             else:
                 defaults = opt.default
         else:
@@ -216,7 +216,9 @@ class _OptFormatter(object):
         for default_str in defaults:
             if default_str.strip() != default_str:
                 default_str = '"%s"' % default_str
-            lines.append('#%s = %s\n' % (opt.dest, default_str))
+            if default_str:
+                default_str = ' ' + default_str
+            lines.append('#%s =%s\n' % (opt.dest, default_str))
 
         self.writelines(lines)
 
diff --git a/tests/test_generator.py b/tests/test_generator.py
index aa274e0..6b99967 100644
--- a/tests/test_generator.py
+++ b/tests/test_generator.py
@@ -85,6 +85,11 @@ class GeneratorTestCase(base.BaseTestCase):
         'multi_opt': cfg.MultiStrOpt('multi_opt',
                                      default=['1', '2', '3'],
                                      help='multiple strings'),
+        'multi_opt_none': cfg.MultiStrOpt('multi_opt_none',
+                                          help='multiple strings'),
+        'multi_opt_empty': cfg.MultiStrOpt('multi_opt_empty',
+                                           default=[],
+                                           help='multiple strings'),
         'multi_opt_sample_default': cfg.MultiStrOpt('multi_opt',
                                                     default=['1', '2', '3'],
                                                     sample_default=['5', '6'],
@@ -408,6 +413,28 @@ class GeneratorTestCase(base.BaseTestCase):
 #multi_opt = 2
 #multi_opt = 3
 ''')),
+        ('multi_opt_none',
+         dict(opts=[('test', [(None, [opts['multi_opt_none']])])],
+              expected='''[DEFAULT]
+
+#
+# From test
+#
+
+# multiple strings (multi valued)
+#multi_opt_none =
+''')),
+        ('multi_opt_empty',
+         dict(opts=[('test', [(None, [opts['multi_opt_empty']])])],
+              expected='''[DEFAULT]
+
+#
+# From test
+#
+
+# multiple strings (multi valued)
+#multi_opt_empty =
+''')),
         ('str_opt_sample_default',
          dict(opts=[('test', [(None, [opts['str_opt_sample_default']])])],
               expected='''[DEFAULT]