Add value only output formattter

It may be useful to have a value only output formatter to perform operationgs like:
   TOKEN=$(openstack token create -c id -f value)
Rather than:
   eval $(openstack token create -c id -f shell)
   TOKEN="${id}"

Change-Id: I7bda3cc1a1d154a05e8e31eed564dae1e82066d6
Closes-Bug: #1292578

3 files changed, 31 insertions, 0 deletions

diff --git a/cliff/formatters/value.py b/cliff/formatters/value.py
new file mode 100644
index 0000000..9910319
--- /dev/null
+++ b/cliff/formatters/value.py
@@ -0,0 +1,15 @@
+"""Output formatters values only
+"""
+
+from .base import SingleFormatter
+
+
+class ValueFormatter(SingleFormatter):
+
+    def add_argument_group(self, parser):
+        pass
+
+    def emit_one(self, column_names, data, stdout, parsed_args):
+        for value in data:
+            stdout.write('%s\n' % str(value))
+        return
diff --git a/cliff/tests/test_formatters_value.py b/cliff/tests/test_formatters_value.py
new file mode 100644
index 0000000..25fb23d
--- /dev/null
+++ b/cliff/tests/test_formatters_value.py
@@ -0,0 +1,15 @@
+#!/usr/bin/env python
+from six import StringIO
+
+from cliff.formatters import value
+
+
+def test_value_formatter():
+    sf = value.ValueFormatter()
+    c = ('a', 'b', 'c', 'd')
+    d = ('A', 'B', 'C', '"no escape me"')
+    expected = 'A\nB\nC\n"no escape me"\n'
+    output = StringIO()
+    sf.emit_one(c, d, output, None)
+    actual = output.getvalue()
+    assert expected == actual
diff --git a/setup.cfg b/setup.cfg
index e019b4f..b7f1529 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -33,6 +33,7 @@ cliff.formatter.list =
 cliff.formatter.show =
     table = cliff.formatters.table:TableFormatter
     shell = cliff.formatters.shell:ShellFormatter
+    value = cliff.formatters.value:ValueFormatter
 
 cliff.formatter.completion =
     bash = cliff.complete:CompleteBash