Handle complex objects in yaml formatter better

this patch adds special handling of objects that have either 'toDict'
or 'to_dict' method, converting those to dictionary before passing
them to pyYaml.

The main immediate aim is to support instances of
openstack.utils.Munch class in the YAML output.

Story: 2010906
Task: 48728
Change-Id: If3718477533987b6b88b27ac639c6689a2e4b327

cliff/formatters/yaml_format.py

@@ -17,6 +17,17 @@ from . import base
 from cliff import columns
 
 
+def _yaml_friendly(value):
+    if isinstance(value, columns.FormattableColumn):
+        return value.machine_readable()
+    elif hasattr(value, "toDict"):
+        return value.toDict()
+    elif hasattr(value, "to_dict"):
+        return value.to_dict()
+    else:
+        return value
+
+
 class YAMLFormatter(base.ListFormatter, base.SingleFormatter):
 
     def add_argument_group(self, parser):
@@ -29,10 +40,7 @@ class YAMLFormatter(base.ListFormatter, base.SingleFormatter):
         items = []
         for item in data:
             items.append(
-                {n: (i.machine_readable()
-                     if isinstance(i, columns.FormattableColumn)
-                     else i)
-                 for n, i in zip(column_names, item)}
+                {n: _yaml_friendly(i) for n, i in zip(column_names, item)}
             )
         yaml.safe_dump(items, stream=stdout, default_flow_style=False)
 
@@ -41,9 +49,5 @@ class YAMLFormatter(base.ListFormatter, base.SingleFormatter):
         import yaml
 
         for key, value in zip(column_names, data):
-            dict_data = {
-                key: (value.machine_readable()
-                      if isinstance(value, columns.FormattableColumn)
-                      else value)
-            }
+            dict_data = {key: _yaml_friendly(value)}
             yaml.safe_dump(dict_data, stream=stdout, default_flow_style=False)

cliff/tests/test_formatters_yaml.py

@@ -22,6 +22,23 @@ from cliff.tests import base
 from cliff.tests import test_columns
 
 
+class _toDict:
+
+    def __init__(self, **kwargs):
+        self._data = kwargs
+
+    def toDict(self):
+        return self._data
+
+
+class _to_Dict:
+    def __init__(self, **kwargs):
+        self._data = kwargs
+
+    def to_dict(self):
+        return self._data
+
+
 class TestYAMLFormatter(base.TestBase):
 
     def test_format_one(self):
@@ -98,3 +115,39 @@ class TestYAMLFormatter(base.TestBase):
         sf.emit_list(c, d, output, args)
         actual = yaml.safe_load(output.getvalue())
         self.assertEqual(expected, actual)
+
+    def test_one_custom_object(self):
+        sf = yaml_format.YAMLFormatter()
+        c = ('a', 'b', 'toDict', 'to_dict')
+        d = ('A', 'B', _toDict(spam="ham"), _to_Dict(ham="eggs"))
+        expected = {
+            'a': 'A',
+            'b': 'B',
+            'toDict': {"spam": "ham"},
+            'to_dict': {"ham": "eggs"}
+        }
+        output = StringIO()
+        args = mock.Mock()
+        sf.emit_one(c, d, output, args)
+        actual = yaml.safe_load(output.getvalue())
+        self.assertEqual(expected, actual)
+
+    def test_list_custom_object(self):
+        sf = yaml_format.YAMLFormatter()
+        c = ('a', 'toDict', 'to_dict')
+        d = (
+            ('A1', _toDict(B=1), _to_Dict(C=1)),
+            ('A2', _toDict(B=2), _to_Dict(C=2)),
+            ('A3', _toDict(B=3), _to_Dict(C=3))
+        )
+        expected = [
+            {'a': 'A1', 'toDict': {'B': 1}, 'to_dict': {'C': 1}},
+            {'a': 'A2', 'toDict': {'B': 2}, 'to_dict': {'C': 2}},
+            {'a': 'A3', 'toDict': {'B': 3}, 'to_dict': {'C': 3}}
+        ]
+        output = StringIO()
+        args = mock.Mock()
+        sf.add_argument_group(args)
+        sf.emit_list(c, d, output, args)
+        actual = yaml.safe_load(output.getvalue())
+        self.assertEqual(expected, actual)