Merge "Make 'FormattableColumn' comparable"

3 files changed, 27 insertions, 0 deletions

diff --git a/cliff/columns.py b/cliff/columns.py
index 6ecef64..b9cac5e 100644
--- a/cliff/columns.py
+++ b/cliff/columns.py
@@ -26,6 +26,11 @@ class FormattableColumn(object, metaclass=abc.ABCMeta):
             self.__class__ == other.__class__ and self._value == other._value
         )
 
+    def __lt__(self, other):
+        return (
+            self.__class__ == other.__class__ and self._value < other._value
+        )
+
     @abc.abstractmethod
     def human_readable(self):
         """Return a basic human readable version of the data."""
diff --git a/cliff/tests/test_columns.py b/cliff/tests/test_columns.py
index 564620d..6bce767 100644
--- a/cliff/tests/test_columns.py
+++ b/cliff/tests/test_columns.py
@@ -33,3 +33,16 @@ class TestColumns(unittest.TestCase):
             u"I made this string myself: ['list', 'of', 'values']",
             c.human_readable(),
         )
+
+    def test_sorting(self):
+        cols = [
+            FauxColumn('foo'),
+            FauxColumn('bar'),
+            FauxColumn('baz'),
+            FauxColumn('foo'),
+        ]
+        cols.sort()
+        self.assertEqual(
+            ['bar', 'baz', 'foo', 'foo'],
+            [c.machine_readable() for c in cols],
+        )
diff --git a/releasenotes/notes/comparable-FormattableColumn-31c0030ced70b7fb.yaml b/releasenotes/notes/comparable-FormattableColumn-31c0030ced70b7fb.yaml
new file mode 100644
index 0000000..f32322e
--- /dev/null
+++ b/releasenotes/notes/comparable-FormattableColumn-31c0030ced70b7fb.yaml
@@ -0,0 +1,9 @@
+---
+features:
+  - |
+    Instances of ``cliff.columns.FormattableColumn`` are now comparable. This
+    allows implementations of ``FormattableColumn`` storing primitive data
+    types or containers with primitive data types to be sorted using the
+    ``--sort-column`` option. Implementations of ``FormattableColumn`` that
+    store other types of data will still need to implement their own rich
+    comparison magic methods.